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Antimicrobial activity of Eucalyptus camaldulensis essential oils and their interactions with conventional antimicrobial agents against multi-drug resistant Acinetobacter baumannii
Abstract
Ethnopharmacological relevance:
Traditional herbal medicine has become an important issue on the global scale during the past decade. Among drugs of natural origin, special place belongs to essential oils, known as strong antimicrobial agents that can be used to combat antibiotic-resistant bacteria. Eucalyptus camaldulensis leaves are traditional herbal remedy used for various purposes, including treatment of infections. The aim of this study was to determine antimicrobial potential of two E. camaldulensis essential oils against multi-drug resistant (MDR) Acinetobacter baumannii wound isolates and to examine possible interactions of essential oils with conventional antimicrobial agents.
Materials and methods:
Chemical composition of essential oils was determined by gas chromatography-mass spectrometry analysis (GC-MS). MIC values of essential oils against A. baumannii strains were estimated by modified broth microdilution method. The components responsible for antimicrobial activity were detected by bioautographic analysis. The potential synergy between the essential oils and antibiotics (ciprofloxacin, gentamicin and polymyxin B) was examined by checkerboard method and time kill curve.
Results:
The dominant components of both essential oils were spatulenol, cryptone, p-cimene, 1,8-cineole, terpinen-4-ol and β-pinene. The detected MICs for the E. camaldulensis essential oils were in range from 0.5 to 2μl mL-1. The bioautographic assay confirmed antibacterial activity of polar terpene compounds. In combination with conventional antibiotics (ciprofloxacin, gentamicin and polymyxin B), the examined essential oils showed synergistic antibacterial effect in most of the cases, while in some even re-sensitized MDR A. baumannii strains. The synergistic interaction was confirmed by time-kill curves for E. camaldulensis essential oil and polymyxin B combination which reduced bacterial count under detection limit very fast, i.e. after 6h of incubation.
Conclusions:
The detected anti-A. baumannii activity of E. camaldulensis essential oils justifies traditional use of this plant. The proven E. camaldulensis essential oil synergistic interactions with conventional antibiotics could lead to the development of new treatment strategies of infections caused by MDR A. baumannii strains in the term of antibiotic dose reduction.
... Phytochemical concentrations were recalculated from µL mL −1 or percentage to µg mL −1 based on their densities (Table 1) to ensure comparability [80]. ...
... The checkerboard method was used to determine interactions between antibiotics and phytochemicals, and binary combinations between different phytochemicals [80]. Before checkerboard testing, the potential synergistic interactions were examined by combining 1/4 × MIC of both agents (pre-checkerboard method). ...
... The Fractional Inhibitory Concentration Index (FICI) [81] was calculated to assess the interaction type between agents: The kinetics of bacterial growth inhibition for synergistic interaction, over a period of time, between volatile phytochemicals and antibiotics were performed using a slightly modified time-kill method [80,82]. Modifications were made during the setup of the experiment, which was conducted in parallel across four test tubes. ...
Background: MSSA and MRSA strains are challenging human pathogens that can develop resistance to antibiotics, highlighting the need for alternative antimicrobial agents. Plant metabolites, particularly volatile phytochemicals, may offer promising antimicrobial properties. The aim was to evaluate the antimicrobial and antibiofilm efficacy of various commercial volatile phytochemicals from the terpene and terpenoid groups against reference MSSA and MRSA strains, focusing on synergistic effects in both binary combinations and combinations with antibiotics. Methods: The microdilution method was used to determine the minimum inhibitory concentrations (MICs) for antibiotics and phytochemicals. The checkerboard method assessed synergistic interactions between phytochemicals and between phytochemicals and antibiotics, while the time-kill method was used to confirm these results. Biofilm quantification was performed using the microtiter plate method to evaluate the effects of phytochemicals, antibiotics, and their binary combinations on the eradication of 48-hour-old biofilms. Results: Carvacrol and thymol demonstrated the strongest anti-staphylococcal activity, while other terpene compounds showed weaker effects. In binary combinations, carvacrol and thymol exhibited synergy against one MSSA strain (FICI = 0.50) and with tetracycline and chloramphenicol (FICI = 0.28–0.50). Synergy was also noted with streptomycin sulfate against one MRSA strain (FICI = 0.31–0.50) and with other antibiotics, including gentamicin (FICI = 0.25–0.50) and oxacillin (FICI = 0.44). Additionally, effective combinations achieved over 50% biofilm removal at both minimum inhibitory and sub-inhibitory concentrations. Conclusions: Results showed that synergy varies based on strain sensitivity to chemical agents, highlighting their potential for personalized therapy. Despite the difficulty in removing preformed biofilms, the findings highlight the importance of combined treatments to enhance antibiotic effectiveness.
... This study highlights that, in addition to being effective against freefloating bacteria, the combinations can enhance the control of biofilms, bacterial structures that hinder the action of conventional antibiotics, or even sanitizers, when present on surfaces. Knezevic et al. (2016) extracted Eucalyptus camaldulensis EO from two different regions of Montenegro -Herceg Novi (EuHN) and Bar (EuB) -and tested them against 23 strains of Acinetobacter baumannii. Among these strains, 20 were hospital isolates, all of which were identified as multidrug-resistant (MDR). ...
... The inhibitory concentrations of EuHN ranged from 0.5 μL/mL to 2 μL/mL, and for EuB, concentrations ranged from 0.5 μL/mL to 1.41 μL/mL. The bactericidal concentrations of EuB ranged between 0.71 μL/mL and 2 μL/mL, and between 0.71 μL/mL to 4 μL/mL for EuHN (Knezevic et al., 2016). ...
... Both EO, when associated with CIP, resulted in a synergistic effect against two of the three MDR isolates evaluated (Aba-4914 and Aba-5055), with FIC index values below 0.5. The same combination exhibited an additive effect on Aba-6673 (FIC index of 0.53); however, the inhibitory concentration of CIP was reported to be reduced to 1/4 of its original inhibitory concentration when combined with the EO and tested against three other A. baumannii isolates (Knezevic et al., 2016). ...
Antibiotics (ATB) revolutionized medicine, but their overuse has led to antimicrobial resistance (AMR), a major public health crisis. Combining ATBs with essential oils (EO) and their derived compounds (EOC) is a notable option to reduce ATB usage. This combinations lowers the required ATB concentration, addressing resistance issues. This review aims to compile knowledge on ATB-EO/EOC combinations and AMR gene transmission. The articles found indicated that most studies are in vitro, using basic microbiological techniques. These methods, while relevant, don't fully explore combination mechanisms and effects. Furthermore, it was observed that the transmission of resistance genes is extremely common, and a single gene can lead to resistance to multiple drugs, even among ATB exclusively used in animal or human health. AMR is widespread, demanding a multifactorial approach. Combinations offer a potential solution to cut ATB usage, but the pervasive AMR underscores the urgency for innovative technologies to restrict ATB use.
... The in vitro effect of each OT-EO combination was determined by calculation of the fractional inhibitory concentration (FIC) and fractional inhibitory concentration index (FIC index ) according to the following formulas [25,26]: FIC index = FIC OT + FIC EO ; FIC = MIC C /MIC I . ...
... Some studies suggest that these compounds may facilitate drug penetration through the outer layers of the cell wall, block the inhibitory effect of protective enzymes, or interfere with metabolic targets of the antibiotic [30][31][32]. Many authors suggest that whole EOs have greater antimicrobial potential than their single active ingredients due to the synergism between their molecules and the diversity of their mechanisms of action [25]. Another study conducted by Lauteri et al. [33] on tetracycline-resistant Salmonella strains demonstrated that combining this antibiotic with EOs from Coridothymus capitatus (olive thyme), Eugenia caryophyllata (clove), and Thymus vulgaris (common thyme) reduced the MIC of tetracycline from 256 to 4 µg/mL due to an increase in the sensitivity of all strains. ...
Tetracyclines have a high resistance percentage in Salmonella spp. of both human and animal origin. Essential oils, such as cinnamon (Cinnamomum zeylanicum), clove (Eugenia caryophyllata), oregano (Origanum vulgare), and red thyme (Thymus zygis), have shown bactericidal activity against this bacterium. However, in many cases, the minimum inhibitory concentration (MIC) exceeds the cytotoxicity limits. The objective of this study was to assess the in vitro efficacy of combining oxytetracycline with essential these oils against field multidrug-resistant (MDR) Salmonella enterica strains. The MIC of each product was determined using the broth microdilution method. The interaction was evaluated using the checkerboard method, by means of the fractional inhibitory concentration index (FICindex) determination. The results showed a positive interaction (synergy and additivity) between oxytetracycline and the four oils tested, resulting in a reduction in both products’ MICs by 2 to 4 times their initial value, in the case of oils, and by 2 to 1024 times in the case of the antibiotic. The combination of oxytetracycline and cinnamon achieved the best results (FICindex 0.5), with a decrease in the antibiotic effective concentration to below the sensitivity threshold (MIC of the combined oxytetracycline 0.5 µg/mL). There was no antagonistic effect in any case, although differences in response were observed depending on the bacterial strain. The results of this study suggest that combining oxytetracycline with cinnamon oil could be an effective alternative for controlling tetracycline-resistant strains of Salmonella. However, its individual use should be further evaluated through in vitro susceptibility tests.
... In human traditions, herbal medicine has played a role in treating and preventing ailments and diseases, bringing wellness to human beings [1]. One of the most widely used plants in traditional remedies is plants of the Eucalyptus genus. ...
... The use of antimicrobial agents prevents the proliferation of microorganisms that cause food spoilage [11]. Some of secondary metabolites produced by various natural sources such as plants have antimicrobial potential against pathogenic microorganisms and can inhibit virulence factors [1]. These compounds with antibacterial properties have been used in food processing, acting as preservatives and preventing the deterioration of food products both in food pathogenic and non-pathogenic microorganisms [19], and have also been used antioxidant, and antitumor activities [44]. ...
Plants play a key role in the treatment and prevention of diseases since ancient times. Eucalyptus has been traditionally used in the treatment of conditions related to the respiratory system, such as flu, colds, sore throats, bronchitis, as well as neuralgia, and stiffness. Eucalyptus camaldulensis has several phytoconstituents such as ellagitannins endowed with bioactivity, including antioxidant and inhibitory potential on various microorganisms causing foodborne diseases. Tellimagrandin I, pedunculagin, castalagin/vescalagin are among the most representative and have activity against pathogens such as Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, and Bacillus cereus. These antioxidant ellagitannins may have potential application in the food, pharmaceutical, and cosmetic industries. The main industrial uses of E. camaldulensis are related to the production of wood, paper, and charcoal, with its leaves and branches considered by-products from these industrial activities. However, these plant by-products could be used to obtain bioactive compounds for the development of new and improved consumer goods. Therefore, the aim of this work was to review the main ellagitannins of E. camaldulensis and their antioxidant and antibacterial activities in foodborne microorganisms, as well as the relevance that these compounds may have in the food industry and related sectors.
... E. globulus and E. radiata essential oils have demonstrated good antibacterial effects in several studies similar to the results observed in the present work with strains from equine wounds [22,23,[25][26][27][28][34][35][36]. Nicodim et al. observed that E. globulus essential oil resulted in a mean diameter of inhibition greater than some commonly used antibiotics against S. aureus [20]. ...
... Although some studies have proposed a new concept to face bacterial resistance, which includes a combination of conventional antibiotic/antiseptic drugs with essential oils [20,23,35,36], in our study, the interpretation of the results regarding mixtures is not so straightforward. In fact, not all the mixtures seem to bring substantial benefits. ...
Considering the increasing antibiotics resistance, there has been a propensity to replace them with antiseptics when it comes to wound management and treatment. Nevertheless, in recent years, there have been reports regarding resistance to antiseptics by some bacterial strains. There is also concern about the environmental impact of these substances. The aim of this study was to compare the antimicrobial efficacy of antiseptics and eucalyptus essential oils on bacterial strains from horse’s wounds. We used twelve Escherichia coli, eight Staphylococcus aureus, two Staphylococcus pseudintermedius, one Staphylococcus vitulinus and one Staphylococcus saprophyticus strains from equine wounds. The effect of Eucalyptus radiata essential oil, Eucalyptus globulus essential oil, povidone-iodine and chlorhexidine gluconate against the isolated strains was evaluated applying the Kirby-Baüer method. Regarding the Escherichia coli strains, E. radiata and the mixture of E. radiata and E. globulus had a better inhibitory effect than antiseptics. E. globulus had a better effect against most Staphylococcus spp. compared to E. radiata. For both Gram-negative and Gram-positive strains tested, chlorhexidine gluconate had a better inhibitory effect than povidone-iodine. The antibacterial efficacy of essential oils highlights their potential to substitute or complement the use of antiseptics and so reduce resistance to antiseptics.
... E. camaldulensis essential oils and extracts are found to be most active against pathogens when they were compared with other species of genus Eucalyptus. Knezevic et al. (2016) demonstrated that terpinen-4-ol, spatulenol, p-cimene, 1, 8-cineole, cryptone, and β-pinene were the most prominent components in E. camaldulensis essential oils. e MICs for E. camaldulensis essential oils were found to be in the range of 0.5-2 μL/mL. ...
... Time-kill curves for E. camaldulensis essential oils with polymyxin B lowered bacterial count under detection limit which was incredibly fast, that is, after 6 hrs of incubation, confirming the synergistic interaction. [59] In most cases, the studied essential oils had a synergistic antibacterial effect when they are used with traditional antibiotics such as polymyxin, ciprofloxacin, gentamicin, and in some situations, they even resensitized MDR A. baumannii isolates. ...
Carbapenem was originally regarded as a cornerstone therapeutic for Gram-negative bacterial infections that could be fatal, but these pathogens are rapidly acquiring resistance to it by various methods such as forming biofilms, mutations in porin channels, overexpression of efflux pumps, altering or modifying antibiotics, and by horizontal gene transfer of resistance biomarkers. Among Gram-negative pathogens, the World Health Organization has prioritized Acinetobacter baumannii as a “pathogen of concern.” A. baumannii strains have a variety of antibiotics resistance pathways, making them resistant to the majority of antibiotics. Antibiotics are used indiscriminately and excessively, causing extensive natural selection pressure and allowing just the most versatile variants of A. baumannii to flourish. Evolutionary changes are unavoidable, but the widespread utilization of antimicrobials in communities, hospitals, and agriculture industries is certainly contributing to the outbreak. Antibiotic resistance has resulted in a number of adverse outcomes such as inadequacy of antimicrobials, persistent infections, and physical ailments that cause the patients to lose momentum, longer stay in the hospital, increased mortality, and morbidity, as well as increased cost that can overburden the patients and even the hospitals. Therefore, optimizing efficient alternate natural antibacterial compounds is a critical aspect of addressing the problem of antibiotic resistance. Various studies (in vitro) done by scientists and researchers have illustrated the efficacy of plant extracts and their essential oils against A. baumannii and other pathogens. The most urgent need is to do research in vivo and more screening of natural products or plant parts, which might lead to the discovery of novel therapeutically efficient antibacterial agents against resistant bacterial infections.
... E. camaldulensis is also a species within the genus Eucalyptus with biological properties, in addition to being tested against MDR strains such as A. baumannii (Jazani et al. 2012). Knezevic et al. (2016) evaluated two types of E. camaldulensis EOs collected from two coastal areas of Montenegro (Europe -Herceg Novi (EuHN) and Bar (EuB)). Fourty-three compounds were identified in these EO, and the most representative were spatulenol (EuHN -18.90%; ...
... In addition, the researchers observed a synergistic interaction when combining the E. camaldulensis EO with ciprofloxacin, producing FICI values below 0.5 μL mL -1 against two A. baumannii isolates (Aba-4914 and Aba-5055) and an additive effect against Aba-6673. Moreover, a synergistic interaction occurred when the EO was tested with gentamicin against Aba-4914, decreasing the concentrations of the antibiotic, as was shown by combining the EO and polymyxin B, which showed synergistic potential against three multi-resistant microorganisms (Knezevic et al. 2016). ...
Respiratory bacterial infections are a cause of morbidity and mortality worldwide; most of these infections respond well to antibiotic therapies, although several factors cause bacteria to become increasingly resistant, leading to a concerning public health problem. Hence, researchers have sought new antibiotics that can replace or enhance the effectiveness of existing drugs. Given this scenario, this review is based on original articles from the PubMed and Science Direct databases published from May 2015 to February 2022 that reported the potential of essential oils, extracts, and formulations containing Myrtaceae and nanoparticles against bacteria that affect the respiratory system.
... These findings align with those reported by Knezevic et al. [31] in Montenegro, wh spathulenol (21.39%) and cryptone (12.15%) were also identified as dominant compoun though in lower proportions. Similarly, Elgat et al. [32] noted that spathulenol constitu 20.84% of the oil, followed by p-cymene (15.16%), 1,8-cineole (12.01%), and sabine (9.73%). ...
This study investigated the phytochemical profile and evaluated the antimicrobial and insecticidal properties of Eucalyptus camaldulensis Dehn. essential oil (EC-EO) from Algeria, using in vitro and in silico approaches. The yield of EC-EO was 0.27%, with gas chromatography-mass spectrometry (GC-MS) revealing spathulenol (58.24%), cryptone (17.22%), and o-cymene (15.53%) as the major compounds. EC-EO exhibited notable antibacterial activity, particularly against Salmonella typhimurium (14 ± 1.00 mm) and Staphylococcus aureus (14.5 ± 0.50 mm). It also showed effective antifungal activity against Penicillium sp. (11.5 ± 0.49 mm), Candida albicans (11.2 ± 0.29 mm), and Aspergillus fumigatus (9.8 ± 0.27 mm). Insecticidal assays against Tribolium castaneum were conducted using contact toxicity, fumigation toxicity, and repellent activity methods. The median lethal concentration (LC50) for contact toxicity was 0.011 μL/insect after 72 h, while the fumigation test had an LC50 of 122.29 μL/L air. Repellent activity tests showed percentage repellency (PR) values exceeding 80% after 6 h. The molecular geometry and electronic properties of the main compounds were studied using density functional theory (DFT) calculations. In addition, the interaction mode and binding affinity of these molecules with three key enzymes involved in antimicrobial activity, DNA gyrase, dihydrofolate reductase (DHFR) and Tyrosyl-tRNA synthetase (TyrRS), were explored by molecular docking.
... The aim of this study was to investigate the anti-A. baumannii activity of 9 previously extracted and characterized essential oils (Aleksic et al., 2014;Knezevic et al., 2016;Lesjak et al., 2016Lesjak et al., , 2018Nikoli c et al., 2016) and to evaluate mechanism of A. baumannii cells inhibition by the most active oils, including previously confirmed potent M. communis and E. camaldulensis essential oils. For this purpose, we focused on cell membrane integrity (e.g. ...
Essential oils are promising antimicrobial agents against various bacteria. The aim of the study was to examine anti-Acinetobacter baumannii activity of nine essential oils and to elucidate essential oil mechanisms of action against this. In total, 8 out of 9 examined different essential oils exhibited activity against multidrug-resistant (MDR) A. baumannii isolates. The best anti-A. baumannii activity expressed Thymus serpyllum, Satur-eja hortensis and Oreganum majorana essential oil (MBC 1.29 to 2.58 mg mL À1), while essential oils of Menta x piperita, Hyssopus officinalis, Foeniculum vulgare and Artemisia dracunculus expressed the same effect in higher concentrations (1.80 to 3.80 mg mL À1). The effect of Juniperus sabina, Juniperus sibirica and S. hortensis essential oils against A. baumannii is for the first time reported here. The mechanisms of Myrtus communis, Eucalyptus camaldulensis, S. hortensis and T. serpyllum essential oils were further examined. The essential oil treatments led to concentration dependent leakage of biomolecules form the cells, causing an increase in the concentrations of lipids, carbohydrates, and proteins in the suspensions. Microstructural observations confirmed the essential oil effect on cell membranes and disruption the membrane integrity, with obvious leakage of intercellular substance, collapsed cells with perforations, debris presence and autoaggregated cells. The subinhibitory concentrations of oils did not obviously changed protein patterns determined by SDS-PAGE. These results indicate that the essential oils, particularly T. serpyllum, S. hortensis, M. communis and E. camaldulensis express its anti-A. baumannii activity via membrane disruption and increased membrane per-meability, representing very promising alternative antibacterial agents against MDR wound isolates.
... A recent study revealed that synthetic compound 3hydroxy benzoic acid (3-HBA) has significant efficacy in inhibiting biofilm formation and virulence factors in MDR Staphylococcus aureus [126]. Similarly, other research studies indicated that various essential oils (EOs) extracted from plants are enriched with key oil components, such as oregano oil (high in carvacrol and thymol), CINNAMON oil (high in eugenol), and Eucalyptus camaldulens oil (high in thymol), have effectiveness against A. baumannii wound infections [127,128]. There are several natural products, including Myrtenol, a bicyclic monoterpene specifically targeting the mature biofilm, diminishes its thickness, and suppresses the virulence factors. ...
... The plant is extensively utilized in traditional treatments for colds, asthma, diarrhea, dysentery, laryngitis, and sore throats [15]. Previously, there was antimicrobial investigation on E. camaldulensis [12,16,17]. Antibiotic-resistant diseases cost approximately up to $29,069 per patient and can lead to an extended length of treatment. ...
Throughout history, medicinal plants have been the primary source for preventing and treating infectious diseases and other health issues. The flowering plant Eucalyptus camaldulensis, also called river red gum, is a member of the Myrtaceae family and has numerous traditional uses. The objectives of the present study were to identify the essential oil components of Eucalyptus camaldulensis using Gas Chromatography Mass Spectrometry (GCMS), and to determine the antioxidant, antidiabetic, and antibacterial activities of ethanol, aqueous, and essential oil extracts from E. camaldulensis leaves. Addtionally, the essential oil constituents that were identified underwent an in silico analysis. The efficacy of various extracts in combat pathogens and free radicals was assessed through the utilization of the 1,1-Diphenyl-2-Picryl Hydrazyl (DPPH), ferric reducing antioxidant 256 AIMS Biophysics Volume 11, Issue 3, 255-280. power (FRAP), α-glucosidase inhibition, and disk diffusion methods. In terms of radical scavenging, reducing power, and α-glucosidase inhibitory activity, the essential oil showed strong antioxidant activity at 84.01 %, 20.1 mmol/g, and 78.2 %, respectively. The essential oil showed a potent antimicrobial action against Staphylococcus aureus and Pseudomonas aeruginosa, with 12 and 14 mm inhibitions, respectively, which were higher than ampicillin's 9 and 6 mm inhibitions, respectively. The GCMS analysis showed that the following chemicals were the most common: cis-11-hexadecenal (10.2%), trans-13-octadecenoic acid (9.5%), and 6-Octadecenoic acid, methyl ester, (Z)-(8.8%). The α-glucosidase enzyme was targeted in a docking study to investigate the antidiabetic properties of the 42 phytochemicals found in the essential oil extract. The compound, namely 5.alpha.-Androstan-16-one, showed the highest binding affinities of −8.6 Kcal/mol during the docking screening of the 42 identified phytochemicals against α-glucosidase. These two compounds show potential as competitive α-glucosidase inhibitors. E. camaldulensis will be a particularly useful source to improve health and fight communicable and non-communicable diseases. Nonetheless, human evaluations of E. camaldulensis safety and effectiveness are necessary, and more well-planned clinical trials are needed to confirm our in vitro and in silico findings.
... The chemical composition (qualitative and semi-quantitative characterization) of the tested oil was determined by gas chromatography-mass spectrometry (GC-MS) at the Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Serbia. Analyses was performed using an Agilent Technologies gas chromatograph coupled with an Agilent Technologies 5975B electron ionization mass-selective detector using the technical conditions as described by Knežević et al. (2016). Data were acquired in scan mode (m/z range 35-400), with solvent delay of 2.30 min, and processed using Agilent Technologies MSD ChemStation software (revision E01.01.335) combined with AMDIS (ver. ...
Background: The increasing difficulties in combating anthelmintic resistance in gastrointestinal nematodes (GINs) of sheep worldwide and the residues of chemical drugs in animal products and the environment necessitate the search for alternatives. Previous studies have shown that plant essential oils (EOs) could be valuable anthelmintic agents. The aim of this study was to evaluate the possibility of using winter savory (Satureja montana L.) EO against sheep GINs through performing in vitro and in vivo efficacy tests and preliminary toxicity studies.
Methods: The chemical composition of the S. montana EO was determined by gas chromatography-mass spectrometry (GC-MS). For the evaluation of anthelmintic potential in vitro, the Egg Hatch Test (EHT) was performed at eight different concentrations (50, 12.5, 3.125, 0.781, 0.195, 0.049, 0.025 and 0.0125 mg/ml). Field efficacy was evaluated using the Faecal Egg Count Reduction Test (FECRT) on two farms where the oil was applied intraruminally to sheep at a mean dose of 150 mg/kg. The toxic effect of the oil was evaluated by physical observation of the tested animals and by collecting blood samples for further haematological and biochemical analyses. Coproculture examination of faecal samples from the tested sheep before and after treatment was also performed to identify the GIN genera present.
Results: Main compounds of the S. montana oil identified by GC-MS analysis were p-cymene (42.8%), carvacrol (28.1%) and y-terpinene (14.6%). The in vitro EHT showed a dose-dependent (R²=0.94) anthelmintic potential of the tested oil with ovicidal activity varying from 17.0-83.3% and determined IC50 value of 0.59 mg/ml. The field efficacy reached 33% (at group level) and 50% (at individual level) at D14 after treatment. In vivo efficacy was significantly higher in farm 2 (FEC above 65% at group level, p<0.05) where sheep were kept in pens during treatment. No toxic effects were observed either in the physical observation of the test animals or in their liver and kidney function.
Conclusion: The moderate efficacy on EHT and FECRT, without adverse effects on the sheep, suggests that S. montana EO is suitable for the control of sheep GINs as part of an integrated parasite management. Further studies should be conducted to further increase efficacy.
... The interaction is considered effective and synergistic if the starting bacterial count (CFU/mL) decreases by ≥ 2 logs after 24 hours of incubation for the combination of essential oil and antibiotic (Knezevic et al, 2016). The antibiotics used in combination with essential oils against A. baumannii bacteria were imipenem, piperacillin/tazobactam, ciprofloxacin, amikacin, and polymyxin B. ...
A espécie N. hihua, conhecida como canela, uma Lauraceae encontrada na América do Sul e na região sul de Mato Grosso do Sul. Neste estudo, relatamos o estudo da ação química, biológica e sinérgica do óleo essencial (OE) de folhas e casca. Na extração do OE foram obtidos rendimentos de 0,49% e 0,55% para cascas e folhas, respectivamente. Para a identificação e quantificação dos constituintes foram realizadas análises cromatográficas por GC-MS e GC-FID. Os resultados das análises de GC-MS foram comparados com as bibliotecas NIST e Adams, e pelo cálculo do índice de retenção de Kovats. Para o OE das folhas, os compostos majoritários foram espatulenol (39,90%), δ-elemeno (5,54%), germacreno D (7,34%), γ-elemeno (16,51%). Para o OE da casca, os principais constituintes foram semelhantes, sendo espatulenol (34,68%), δ-elemeno (16,75%) e germacreno D (7,73%). Através de TLC foi realizado o isolamento do espatulenol para o óleo da casca. Sua determinação estrutural foi realizada por espectroscopia de RMN de 13C e 1H. Nas avaliações antimicrobianas contra a bactéria Acinetobacter baumannii, o OE de ambas as amostras não apresentou atividade. Porém, no teste de concentração inibitória mínima (CIM), apresentou fraca atividade para a bactéria S. aureus (2250 µg/mL) e forte atividade para E. faecalis (281,25 µg/mL). No teste de sinergismo, foi observada eficiência das amostras de OE da casca e das folhas contra a bactéria gram-negativa Acinetobacter baumannii, portadora do gene de resistência blaoxa-23. A redução do crescimento bacteriano foi observada em associação com os antibióticos polimixina B, imipenem e amicacina.
... For the identification of MBC, 10 μL was taken from the MIC indicator well and from three previous wells, which were inserted in plates with Nutrient Agar using the microdrop technique (de Almeida et al., 2023;Knezevic et al., 2016). ...
The consumer demand for a reduction in the use of synthetic additives in food has been providing a greater search and incentive for the food industries to use new alternatives for food preservation. Among them, there is the initiative to use essential oils (EOs) due to their antimicrobial properties, coming from specific compounds in their compositions. However, in view of limitations related to the use of EOs, as well as their susceptibility to oxidation and degradation, the possibility arises of employing protection methods such as microencapsulation to minimize the impairment of the benefits associated with the application of EOs. This study aimed to examine the antimicrobial effect of turmeric and nutmeg EOs against microbial strains of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella spp., as well as the microparticles of the EOs involved. Analyses of the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC), and the developed microparticles, as well as the verification of the synergistic inhibitory action between these oils, were carried out. For free oils, antimicrobial action was evidenced against the vast majority of microorganisms tested, with free nutmeg EO having a better antimicrobial effect than free turmeric oil. In contrast, for encapsulated oils, only antimicrobial action was noted against strains of Listeria. Furthermore, the synergism of free oils did not potentiate the antimicrobial action. Regarding the alternative of microencapsulation of EOs, it was obtained that the results in which chitosan was used as wall material were more promising than when gelatin was used as wall material.
... The EOs tested in the present study were obtained from the following two producers: BIOSS, Serbia -orange (Citrus sinensis (L.) Osbeck), citron (Citrus medica L.), hyssop (Hyssopus o cinalis L.) and sage (Salvia o cinalis L.) as well as the Institute for Field and Vegetable Crops, Novi Sad, Serbia -wild mint (Mentha spicata L.), coriander (Coriandrum sativum L.), lavender (Lavandula angustifolia Mill.) and basil (Ocimum basilicum L.). Their chemical composition (qualitative and semiquantitative characterization) was determined by gas chromatography-mass spectrometry (GC-MS), using the following technical conditions: injection volume of EO 1 µL; injector temperature 250°C; split ratio 1:10; carrier gas helium; ow rate: 1 mL/min; capillary column: HP-5 (30 m × 0.25 mm, 0.25 µm); temperature program 50-270°C; ion source temperature 230°C; electron energy 70 eV; quadrupole temperature 150°C (35). Compounds were identi ed by comparison of mass spectra with data libraries (Wiley Registry of Mass Spectral Data, 7th ed., and NIST/EPA/NIH Mass Spectral Library 05) and con rmed by comparison of arithmetic retention indices (AI) with literature data (36). ...
Background
Gastrointestinal nematodes (GINs) represent major obstacle to modern small ruminant farming due to their various negative effects on animal health, welfare and productivity. The exclusive use of commercial, synthetic anthelmintics is no longer a sustainable option due to the development of resistance in GINs and the problem of residues of these drugs in animal products and the environment. The aim of this study was to investigate in vitro the phytotherapeutic properties of seven different plant essential oils (EOs): Citrus x sinensis (L.) Osbeck, Citrus medica (L.), Mentha spicata (L.), Ocimum basilicum (L.), Hyssopus officinalis (L.), Salvia officinalis (L.) and Lavandula angustifolia Mill. against GINs in sheep.
Methods
First, the chemical composition (qualitative and semi-quantitative characterization) of the tested EOs was determined by gas chromatography–mass spectrometry (GC–MS) analysis. Their anthelmintic potential was evaluated in vitro using the egg hatch test, which was performed at eight different concentrations of each oil: 50, 12.5, 3.125, 0.781, 0.195, 0.049, 0.025 and 0.0125 mg/ml. Finally, a coproculture examination was performed to determine the genera of GIN against which the oils were tested.
Results
Some of the most frequently identified compounds in GC-MS analyses were limonene, myrcene, α- and β- pinene, γ-terpinene, sabinene, linalool, eucalyptol, terpinen-4-ol, camphor, etc., with their total number per oil varying from 8 (C. sinensis) to 42 (O. basilicum). The tested EOs showed a dose-dependent (R² close to 1) ovicidal activity, with O. basilicum (23.3–93.3%, IC50 = 0.08 mg/ml), M. spicata (13.0-92.7%, IC50 = 0.07 mg/ml) and H. officinalis (42.7–91.3%, IC50 = 0.19 mg/ml) being the most effective. The high activity of these oils could be attributed to the high content of the monoterpene alcohol linalool and the terpenoid ketones carvone and pinocamphone. The least effective were S. officinalis (15.0–89.0%, IC50 = 0.53 mg/ml) and C. medica 12.3–95.0% (IC50 = 2.52 mg/ml). Four genera of sheep GINs were identified on coproculture examination, i.e. Haemonchus 43%, Trichostrongylus 35%, Teladorsagia 17% and Chabertia 5%.
Conclusion
The results obtained suggest that EOs tested, especially wild mint, basil and hyssop, could represent a valuable alternative in the control of GINs in sheep, which could help to reduce the use of chemical drugs. Future field trials should be performed to confirm these findings.
... In traditional medicine, plant extracts from medicinal and aromatic plants or phenolic substances from these plants have been used for centuries. Medicinal plants are used in primary health care for their antimicrobial, anticancer, antithrombotic, antidiabetic, and many disease-therapeutic properties (Gong et al., 2020;Senizza et al., 2020;Man et al., 2019;Knezevic et al., 2016). Isorhamnetin is an important compound obtained from some of these medicinal plants (Ren et al., 2019;Pengfei et al., 2009;Teng et al., 2006). ...
Isorhamnetin (3’-methylquercetin) is an important flavonoid produced as a secondary metabolite from medicinal and aromatic plants due to its pharmacological and therapeutic properties. Thus far, the anticancer, antiallergic, antiinflammatory, antioxidant, antiviral, and antimicrobial properties of isorhamnetin have been evaluated in indirect studies conducted with isorhamnetin found in plant extracts or essential oils or direct studies performed with pure isorhamnetin. However, this is the first study in the literature on the antifungal activity of 97% pure isorhamnetin against C. tropicalis, C. albicans, C. krusei, and C. parapsilosis using two assays including agar dilution and broth microdilution methods. This study showed that isorhamnetin has a significant inhibitory effect against all Candida species used. The minimum inhibitory concentration (MIC) value of isorhamnetin against C. tropicalis, C. albicans, C. krusei, and C. parapsilosis was 1.875 mg/mL, the same for all yeast strains. These results have opened a new horizon regarding the usability of isorhamnetin as a pharmacological therapeutic antifungal agent.
... Variation in the chemical composition of essential oils is reported by several studies [25][26][27]. It may be associated with abiotic factors such as luminosity, temperature, rainfall, nutrition, harvest time, collection time, as well as harvest and postharvest techniques [28]. ...
Eucalyptus are trees native to Australia and have been cultivated in various regions of the world. In its worldwide expansion, several native and exotic insects began to use these plants for their survival. Leptocybe invasa Fisher & La-Salle, 2004 (Hymenoptera: Eulophidae) is a gall wasp that lay eggs into leaves, young branches, and petioles causing galls; however, there are resistant and susceptible eucalyptus genotypes to gall formation. This study aimed to compare the chemical composition of eucalyptus genotypes and relate it to resistance and susceptibility to gall formation. Leaf oils were extracted by steam distillation and oil compositions were analyzed. The essential oils of eucalyptus genotypes resistant to gall formation had 12 constituents, which do not occur in susceptible genotypes, probably one of the factors that contributes to the resistance of these plants to gall formation. Thus, we suggest an early evaluation of resistant or susceptible eucalyptus genotypes, based on the chemical composition of the essential oils of these plants, avoiding economic losses of planting susceptible genotypes.
... In this study, M. tomentosa topical cream with Eucalyptus oil as a permeation enhancer was formulated, and the anti-nociceptive and anti-inflammatory effects of the formulation were investigated [15]. The study uses the synergistic interaction between M. tomentosa and Eucalyptus oil to produce a potent anti-inflammatory and anti-nociceptive topical cream [16]. Presently and to the best of our knowledge, no M. tomentosa and Eucalyptus oil cream has been formulated to investigate its anti-inflammatory or antinociceptive properties. ...
Background: Pain is a noxious, sensory, and emotional experience due to intense stimuli. Pain is intimately linked with nociception. The clinical therapies available at the moment for pain are tricyclic antidepressants, non -steroidal anti-inflammatory drugs, and opioids. There is a need to develop and investigate safer alternatives that minimise the chances of psychological or physical drug dependence and drug dose tolerance. The purpose of this research is to develop an anti-inflammatory and anti-nociceptive formulation (Markhamia tomentosa cream co-formulated with Eucalyptus oil as a permeation enhancer) and evaluate its efficacy. Methods: In this study, Markhamia tomentosa was extracted from its leaves using maceration technique. A qualitative screening of the Markhamia tomentosa ethanolic extract (EEMT) was carried out. Five emulsions (A1-A5) containing varying compositions of Markhamia tomentosa were developed, and a negative control (an emulsion that did not contain Markhamia tomentosa or Eucalyptus oil) was also developed using fusion method. The anti-inflammatory and anti-nociceptive properties of the topical creams were evaluated using mice paw-licking and xylene-induced ear oedema tests. Diclofenac and aspirin administered at 20 mg/kg and 50mg/kg orally, respectively, were used as standards. All experiments were carried out in triplicates. Results: The phytochemical investigation of the Markhamia tomentosa extract showed a marked presence of key phyto-constituents such as saponins, flavonoids, alkaloids, and terpenoids. A1 and A2 had significantly higher percentage of nociception inhibition at phase I—neurogenic and phase II—inflammatory stages compared to Diclofenac 20 mg/kg. A1 and A3 had anti-inflammatory properties more potent than Aspirin 50mg/kg. In both tests, the negative controls did not show any level of potency. All results in this investigation were expressed as mean ± S.D (n=3) and (p<0.05) for all data sets. Formulation A1 had the highest concentration of EEMT. No rash, erythema, or oedema was observed in the Draize test implying that the formulations are safe for topical application. Conclusion: Markhamia tomentosa and eucalyptus oil cream showed potent anti-nociceptive and anti-inflammatory activity. Markhamia tomentosa cream co-formulated with Eucalyptus oil as a permeation enhancer can be used effectively as a non-opioid, anti-nociceptive, and anti-inflammatory cream topically for pain and its symptoms
... At the end of incubation, a reading was performed, and the following criteria were considered: sections with microbial growth indicated bacteriostatic activity of the essential oil in question at the analyzed concentration, and sections with no microbial growth showed bactericidal activity. The well with the lowest concentration that exhibited a bactericidal effect was recorded as having MBC [23]. ...
Staphylococcus aureus is a major cause of subclinical mastitis in dairy cows, and its development of antibiotic resistance has limited treatment efficacy. Essential oils (EOs) are natural products with a wide range of antimicrobial properties that could be used to treat bovine mastitis. This study aims to investigate the antimicrobial activity of EOs against S. aureus isolated from subclinical bovine mastitis cases in the State of São Paulo—Brazil. A total of 14 S. aureus isolates were selected, based on the presence of biofilm-forming genes (icaA, icaD, and bap), and were cultured to a final concentration of 103 CFU.mL−1 for the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) analysis of five EOs (Citrus aurantium bergamia—bergamot, Copaifera reticulata—copaiba, Foeniculum vulgare—fennel, Zingiber officinale—ginger, and Ocimum basilicum—basil). The chemical compositions of the EOs were characterized using gas chromatography coupled with a mass-selective detector (GC/MSD). Basil and bergamot EOs exhibited the highest antimicrobial activity against S. aureus strains, with mean MIC/MBC values of 1.561 ± 0.223/2.806 ± 0.255 mg.mL−1 and 2.782 ± 0.228/4.396 ± 0.198 mg.mL−1, respectively. The primary compounds in basil EO were methyl-chavicol, linalool, and α-humulene, while bergamot EO predominantly contained linalyl acetate, limonene, and linalool. This research highlights the potential of basil and bergamot EOs as natural antimicrobial agents for treating bovine mastitis caused by S. aureus, offering a potential alternative to traditional antibiotics and contributing to animal welfare and public health. In addition, it emphasizes the need for further studies to validate the long-term effects, optimal dosages, and application methods.
... The LB255 molecule revealed important properties for Gram-positive bacteria such as Bacillus subtilis and Staphylococcus aureus for MRSA FAD209P strains [34]; primarily, the two carbonyl groups are essential for antibacterial activity [37]. ...
Staphylococcus aureus is a microorganism with high morbidity and mortality due to antibiotic-resistant strains, making the search for new therapeutic options urgent. In this context, computational drug design can facilitate the drug discovery process, optimizing time and resources. In this work, computational methods involving ligand- and structure-based virtual screening were employed to identify potential antibacterial agents against the S. aureus MRSA and VRSA strains. To achieve this goal, tetrahydroxybenzofuran, a promising antibacterial agent according to in vitro tests described in the literature, was adopted as the pivotal molecule and derivative molecules were considered to generate a pharmacophore model, which was used to perform virtual screening on the Pharmit platform. Through this result, twenty-four molecules were selected from the MolPort® database. Using the Tanimoto Index on the BindingDB web server, it was possible to select eighteen molecules with greater structural similarity in relation to commercial antibiotics (methicillin and oxacillin). Predictions of toxicological and pharmacokinetic properties (ADME/Tox) using the eighteen most similar molecules, showed that only three exhibited desired properties (LB255, LB320 and LB415). In the molecular docking study, the promising molecules LB255, LB320 and LB415 showed significant values in both molecular targets. LB320 presented better binding affinity to MRSA (−8.18 kcal/mol) and VRSA (−8.01 kcal/mol) targets. Through PASS web server, the three molecules, specially LB320, showed potential for antibacterial activity. Synthetic accessibility (SA) analysis performed on AMBIT and SwissADME web servers showed that LB255 and LB415 can be considered difficult to synthesize and LB320 is considered easy. In conclusion, the results suggest that these ligands, particularly LB320, may bind strongly to the studied targets and may have appropriate ADME/Tox properties in experimental studies.
... The antimicrobial activity of this EO is mainly attributed to the presence of terpenes, especially of the sesquiterpenes group. In summary, when the combinations of EO with antibiotics were analyzed, it was found that the most used antibiotics were cipro oxacin and gentamicin [49, [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85]. Regarding antifungals, uconazole and amphotericin B were the most used [76][77][78][79][84][85][86][87][88]. ...
Natural products derived from plants play an important role in the development of antimicrobial agents. Antimicrobials are of interest both in the pharmaceutical industry to prevent or fight infections, and in the food industry for their ability to extend the shelf life of food. Although numerous plant extracts and their natural products (metabolites) have demonstrated antimicrobial potential, they still have numerous limitations for being used as antimicrobials. Among them is the genetic variability of the plants, which can be influenced by soil conditions; the difficulty to isolate biocompounds; the low yield of the extract or natural product; the low stability and poor water solubility; and, finally, the weak antimicrobial potency compared to commercial antimicrobials. Due to the great biodiversity and the growing problem of microbial resistance to current drugs, numerous research groups are seeking to improve the antimicrobial activity of plant extracts or their metabolites by means of different techniques. Some of the techniques are the combination of antimicrobial substances in search of synergy, the formation of inclusion complexes with cyclodextrins, and the elaboration of polymeric or solid lipidic nanoparticles, nanoemulsions. Several antimicrobial combinations, as well as different formulations, have proven useful in enhancing the proven biological activity of natural products. This chapter will discuss the main results obtained, the natural products studied in recent years, the field of application, as well as the difficulties and prospects for this field of research.KeywordsAntimicrobial synergismHybrid combinationsNatural antimicrobialsPhytochemicals nanoencapsulated
... Speci cally, studies have demonstrated that when EO is used in combination with antibiotics against multidrug-resistant bacteria, these organisms regain susceptibility to antibiotics. (16, [20][21][22]. Interestingly, however, EOs displayed limited antibacterial activity against bene cial bacteria such as lactic acid-producing bacteria (23)(24)(25). ...
Five essential oils (EOs) were previously characterized in vitro and identified as candidate EOs for the development of an intranasal EO spray to mitigate bovine respiratory disease (BRD) pathogens. In the present study, these EOs were evaluated for their potential to (i) reduce BRD pathogens, (ii) modulate nasopharyngeal microbiota, and (iii) influence animal performance, feeding behavior and immune response when administered intranasally to feedlot cattle. Forty beef steer calves (7–8 months old, Initial body weight = 284 ± 5 kg [SE]) received either an intranasal EO spray (ajowan, thyme, fennel, cinnamon leaf, and citronella) or PBS (Control; n = 20/group) on day 0. Deep nasopharyngeal swabs were collected (days − 1, 1, 2, 7, 14, 28 and 42) and processed for 16S rRNA gene sequencing, qPCR, and culturing. Significant effects of EO on community structure (d1), microbial richness and diversity, and relative abundance of some dominant phyla (d1, d2, and d14), and the overall interaction network structure of the nasopharyngeal microbiota were detected. The EO calves had reduced abundance of Mannheimia (4.34% vs. 10.4%) on d2, and M. haemolytica prevalence on d7 as compared to control calves. Feed intake, average daily gain, feeding behavior and blood cell counts were not affected by EO treatment. Overall, a single intranasal dose of EO spray resulted in moderate modulation of nasopharyngeal microbiota and short-term inhibition of Mannheimia while not influencing animal performance, feeding behavior or immune response. Our study, for the first time, shows the potential use of intranasal EO to mitigate BRD in feedlot cattle.
... When the strain was exposed to the same concentration of Polymyxin B with 0.5 μg ml −1 of Eucalyptus camaldulensis (river red gum) EO, the population reached levels below the experimental detection limit (2 log CFU ml −1 ) in 6 h. In the same period, the treatment with Polymyxin B alone presented a population of over 7 log CFU ml −1 (Knezevic et al., 2016). ...
Several countries have shown an increased prevalence of drug resistance in animal production due to the indiscriminate use of antibiotics and antiparasitics in human and veterinary medicine. This article aims to review existing methods using naturally occurring essential oils (EOs) and their isolated compounds (EOCs) as alternatives to antimicrobials and antiparasitic compounds in animal production and, consequently, to avoid resistance. The most-reported mechanism of action of EOs and EOCs was cell membrane damage, which leads to the leakage of cytoplasmic content, increased membrane permeability, inhibition of metabolic and genetic pathways, morphologic changes, antibiofilm effects, and damage to the genetic material of infections. In parasites, anticoccidial effects, reduced motility, growth inhibition, and morphologic changes have been reported. Although these compounds regularly show a similar effect to those promoted by traditional drugs, the elucidation of their mechanisms of action is still scarce. The use of EOs and EOCs can also positively influence crucial parameters in animal production, such as body weight gain, feed conversion rate, and cholesterol reduction, which also positively impact meat quality. The application of EOs and EOCs is enhanced by their association with other natural compounds or even by the association with synthetic chemicals, which has been found to cause synergism in their antimicrobial effect. By reducing the effective therapeutical/prophylactic dose, the chances of off-flavors – the most common issue in EO and EOC application – is greatly mitigated. However, there is very little work on the combination of EOs and EOCs in large in vivo studies. In addition, research must apply the correct methodology to properly understand the observed effects; for example, the use of only high concentrations may mask potential results obtained at lower dosages. Such corrections will also allow the elucidation of finer mechanisms and promote better biotechnologic use of EOs and EOCs. This manuscript presents several information gaps to be filled before the use of EOs and EOCs are fully applicable in animal production.
... Antimicrobial activity of E. torquata essential oils Eucalyptus essential oils endowed antimicrobial action against a large spectrum of bacteria and fungi which consist to its therapeutic properties as a promising alternative to drugs for several diseases and disorders (Zhang et al., 2010;Barbosa el al., 2016;Dhakad et al., 2018). Additionally, the possible interactions of Eucalyptus essential oils with conventional antimicrobial agents was studied that could lead to new treatment strategies involving reduced antibiotic doses and for higher therapeutic efficacy (Knezevic et al., 2016;Scazzocchio et al., 2016;Al-Qaysi el al., 2020). The bioactivity of Eucalyptus essential oils may be due to their monoterpene components; in fact, antimicrobial activity could be attributed to the presence of compounds such as 1,8-cineole, α-pinene, β-pinene and limonene (Dhakad et al., 2018). ...
Eucalyptus has become one of the most widely planted genera in the world because of its tolerance to a wide range of soil types and climates, as well as for its many industrial, commercial and medicinal uses. Eucalyptus torquata Luehm. is a plantation species frequently planted in semi-arid and arid regions for its ecological, forestry, ornamental and melliferous interests. Based on literature, drought tolerance of this species was mostly directed to adaptation mechanisms. Physiological investigations reveal the importance of stomatal closure and increased solute contents suggesting that osmotic adjustment is one of the main responses to drought in E. torquata. On the other hand, it showed low sensitivity to salt stress. This paper also highlights the immense benefits of E. torquata which contains essential oils with variable chemical composition and rich essentially in 1,8-cineole, torquatone, α-pinene, trans-myrtanol, α-eudesmol, β-eudesmol, globulol, trans-pinocarveol and aromadendrene. These oils, as well as the methanol and aqueous extracts possess a wide variety of bioactivities of great importance which are particularly valuable as antibacterial and antifungal agents also have a strong toxicity against insects and mites in addition to antiproliferative and cytotoxic effects against different types of cancer cells.
... It is reported that γ-terpinene and β-phellandrene have antifungal and insecticidal properties [33][34][35]. Moreover, a variety of monoterpenes and sesquiterpenes have been confirmed to have significant antibacterial potentials [36]. In view of the biological activities of the aforementioned components, we speculated that NI-EO may also have antibacterial activity. ...
Notopterygium incisum Ting ex H. T. Chang (N. incisum) is a precious Chinese traditional medicine distributed in high-altitude regions of southwest China. The aim of this study was to investigate the composition, antibacterial activity, and cytotoxicity of essential oil from aerial parts of N. incisum. N. incisum essential oil (NI-EO) was extracted by hydro-distillation, and gas chromatography/mass spectrometry (GC–MS) analysis showed that the major components of NI-EO were D-limonene (18.42%) and γ-terpinene (15.03%). The antibacterial activity and mechanism study showed that the diameters of inhibition zone (DIZs) of NI-EO against E. coli and S. aureus were 14.63 and 11.25 mm and the minimum inhibitory concentrations were 3.75 and 7.5 μL/mL, respectively. NI-EO not only caused intracellular biomacromolecule leakage and cell deformation by destroying bacterial cell wall integrity and cell membrane permeability, but also degraded the mature biofilm. The low toxicity of NI-EO was demonstrated in an assay on bovine mammary epithelial cells. These results implied that NI-EO was mainly composed of monoterpenes and sesquiterpenes and had excellent antibacterial activity and showed low levels of cytotoxicity. It is expected to be applied as a natural antibacterial agent in the future.
... Antimicrobial activity of E. torquata essential oils Eucalyptus essential oils endowed antimicrobial action against a large spectrum of bacteria and fungi which consist to its therapeutic properties as a promising alternative to drugs for several diseases and disorders (Zhang et al., 2010;Barbosa el al., 2016;Dhakad et al., 2018). Additionally, the possible interactions of Eucalyptus essential oils with conventional antimicrobial agents was studied that could lead to new treatment strategies involving reduced antibiotic doses and for higher therapeutic efficacy (Knezevic et al., 2016;Scazzocchio et al., 2016;Al-Qaysi el al., 2020). The bioactivity of Eucalyptus essential oils may be due to their monoterpene components; in fact, antimicrobial activity could be attributed to the presence of compounds such as 1,8-cineole, α-pinene, β-pinene and limonene (Dhakad et al., 2018). ...
Eucalyptus has become one of the most widely planted genera in the world because of its tolerance to a wide range of soil types and climates, as well as for its many industrial, commercial and medicinal uses. Eucalyptus torquata Luehm. is a plantation species frequently planted in semi-arid and arid regions for its
ecological, forestry, ornamental and melliferous interests. Based on literature, drought tolerance of this species was mostly directed to adaptation mechanisms. Physiological investigations reveal the importance of stomatal closure and increased solute contents suggesting that osmotic adjustment is one of the main responses to
drought in E. torquata. On the other hand, it showed low sensitivity to salt stress. This paper also highlights the immense benefits of E. torquata which contains essential oils with variable chemical composition and rich essentially in 1,8-cineole, torquatone, α-pinene, trans-myrtanol, α-eudesmol, β-eudesmol, globulol, trans�pinocarveol and aromadendrene. These oils, as well as the methanol and aqueous extracts possess a wide variety of bioactivities of great importance which are particularly valuable as antibacterial and antifungal agents also have a strong toxicity against insects and mites in addition to antiproliferative and cytotoxic effects against different types of cancer cells.
... In another study, Tsai reported the activity of Scutellaria barbata against A. baumannii (Tsai et al., 2018). Volatile oil from Cinnamon and Eucalyptus camaldulensis essential oil also showed potent antibacterial activity against A. baumannii (Intorsoot et al., 2017, Knezevic et al., 2016. Ellagic acid (EA) is mainly found in vegetables and fruits, including pomegranates, strawberries, walnuts and raspberries (Rios et al., 2018). ...
Acinetobacter baumannii infections have come to the surface in huge numbers in the recent decades. Furthermore, A. baumannii has adopted great ability to nullify the majority of currently available antibiotics. With the purpose of finding a nontoxic and efficient therapeutic agent, we analyzed the activity of Ellagic acid (EA) against the multidrug-resistant A. baumannii. EA not only demonstrated its activity against A. baumannii, but also inhibited the biofilm formation. Since EA shows poor solubility in an aqueous environment, a lipid nanoparticle-based (liposomal) formulation of EA (EA-liposomes) was prepared and its effectiveness was assessed to treat bacterial infection in the immunocompromised murine model. Therapy with EA-liposomes imparted greater protection to infected mice by increasing the survival and decreasing the bacterial load in the lungs. A. baumannii infected mice treated with EA-liposomes (100 mg/kg) showed 60% survival rate as compared to 20% of those treated with free EA at the same dose. The bacterial load was found to be 32778 ± 12232 in the lungs of EA-liposomes (100 mg/kg)-treated mice, which was significantly lower to 165667 ± 53048 in the lung tissues of free EA treated mice. Likewise, EA-liposomes also restored the liver function (AST and ALT) and kidney function parameters (BUN and creatinine). The broncho-alveolar fluid (BALF) from infected mice contained greater quantities of IL-6, IL-1β and TNF-α, which were significantly alleviated in EA-liposomes treated mice. These findings together support the possible implication of EA-liposomes to treat A. baumannii infection, especially in immunocompromised mice.
... Since ancient times plants have been used as antimicrobial agents in the treatment of many infections [10]. Since, in many cases, herbal medicines are cheaper and have fewer side effects than chemical drugs, today, biological compounds of plant origin are considered an important branch of drug treatment of infectious diseases. ...
Background
Multidrug-resistant (MDR) Gram-negative bacteria such as Acinetobacter baumannii pose an increasingly severe threat. Finding new therapeutic strategies such as herbal remedies is a vital priority, especially in combination with nano gels which have recently been widely used in medical purposes and drug delivery systems.
Objective
In this study, evaluated the physicochemical properties and effects of mutagenicity synthesizing Mentha Piperita Essential Oils loaded in chitosan nanoparticles (MPEO- CsNPs), which is referred to as an antimicrobial agent for inhibiting biofilm formation of Acinetobacter baumannii on the catheter surface.
Method
Mentha piperita essential oils loaded in chitosan nanoparticles (MPEO- CsNPs) and the physicochemical properties of MPEO-CsNPs were analyzed by Scanning Electron Microscopy (SEM) and Differential Calorimetry Scanning (DCS). The Minimum Inhibitory Concentration (MIC), the Minimum Bactericidal Concentration (MBC), and the Inhibitory Concentration (MBIC50) of MPEO- CsNPs against the standard strain of Acinetobacter baumannii were investigated. The amount of biofilm formation in the presence and absence of MPEO- CsNPs on the catheter surface was analyzed. The bap gene expression was studied as the primary leading indicator of biofilm formation using the real-time PCR technique. The effects of mutagenicity according to the Ames test were investigated.
Results
The results showed that the synthesized MPEO- CsNPs at equivalent concentrations had lower MIC than sodium azide. MIC and MBC levels were reported to be 3.12 and 12.48 µg / ml, respectively. MBIC50 was calculated to be 2.69%, which it was approximately twofold compared to the control that was treated with no MPEO concentration. The adherence of bacterial cells to the catheter surface had high sensitivity to the MPEO- CsNPs, while when treated with unloaded CNPs, it had no inhibitory effect on adherence activity. It was observed that with increasing the concentration of the MPEO- CsNPs, expression of the bap gene decreased.
Conclusion
This study showed that chitosan-peppermint nanoparticles could be used as a safe, compatible, and preventive coating in the design and manufacture of hospital catheters and other medical devices.
... Moreover, E. globulus leaf ethanolic extract incorporated ointment showed significant activity on different wound models [42]. In another related study reported that E. camaldulensis leaves are traditional herbal remedies used for various purposes, including the treatment of wound infections with a broad-range antimicrobial properties [43]. Fig. 9 Whole blood clotting kinetics of phenolic-rich extracts fortified and control composite after 5 min (A) and 10 min (B), statistical significance for the observed mean difference between control blood alone, control, and test composite was determined using one-way ANOVA followed by Dunnett's test (**** p < 0.001 vs. control blood alone) Content courtesy of Springer Nature, terms of use apply. ...
Contagious wound infection has become one of the most common challenges concomitants with the wounds, causing severe inflammatory responses, and ultimately delaying skin tissue regeneration. Herein, a phenolic-rich Eucalyptus camaldulensis leaf hydrophobic (ECG) and hydrophilic extract (ECY), in varied content was fortified within a hypromellose polymeric matrix was characterized, and further targeted as an effective antioxidative, antimicrobial, anti-inflammatory, and hemostasis dressing. Infrared spectroscopy and thermal analysis of ECG and ECY fortified composite indicated significant hydrogen bonding-based cross-linking, while scanning electron microscopy image showed a porous structure. The chromatography profiling demonstrated 0.022 ± 0.02 and 0.027 ± 0.01 µg/mg of quercetin for the ECG and ECY fortified composite, respectively. The antibacterial and antioxidant activity of extract incorporated composite was significantly (p < 0.001) higher than that of control. Biocompatibility results revealed that composites were compatible with > 80% viability of HaCaT and RAW 264.7 cells. The results of the blood-coagulation and clotting kinetics showed time and dose-dependent hemostasis. Eucalyptus camaldulensis leaf hydrophilic extract incorporated composite significantly (p < 0.001) attenuated the nitrite production against lipopolysaccharides-stimulated macrophage cells. Moreover, the HaCaT cell showed migration of 43.59 ± 1.26 (%) and 48.12 ± 1.85 (%) treated with ECG and ECY incorporated composite after 24 h, respectively. Overall, the hydrophilic extract-incorporated composites showed multifarious biological properties, suggesting their potential for comprehensive wound healing dressing.
Eucalyptus Essential oils has a variety of bioactivities as fungicidal, bactericidal, insecticidal and other therapeutic properties . This investigation was conducted to assess the antifungal properties of Eucalyptus camaldulensis essential oil alone and in combination with clotrimazole against Aspergillus spp that isolated from patients. The in laboratory results appeared that the development of Aspergillus spp was discouraged by the essential oil at all tested concentration (100 , 50 and 25%) and the effect was increased with the increasing of concentration. The antifungal drugs clotrimazole , itraconzole and griseofulvin also affect the development of Aspergillus spp and the fungus A. fumigatus was less sensitive to essential oil and drugs than the other species of Aspergillus. The outcome shown that the combination of clotrimazol with essential oil was more effective than each one alone and the combination enhanced the antifungal activity with an additive interaction.
Dill, also known as Anethum graveolens, is a botanical species with an annual life cycle and a branching structure. It is a significant part of Ayurvedic medicine and is used as a spice, flavor enhancer, and essential oil supplier. Dill seeds have carminative, stomachic, and diuretic properties. The volatile components of dill seeds and plants are diverse, with carvone being the main odorant. Other substances found in seeds include steroids, phenolic acids, flavonoids, and coumarins. Dill is used in traditional herbal therapy to treat various ailments, including respiratory issues, stomach discomfort, digestive disorders, and low blood sugar and cholesterol. It also has pharmacological benefits, including hypolipidemic, anticancer, antidiabetic, antispasmodic, antibacterial, anti-inflammatory, antioxidant, and anti-infertility benefits. Numerous studies have confirmed these effects.
Acinetobacter baumannii ( A. baumannii ) is a Gram‐negative, nonmotile, and aerobic bacillus emerged as a superbug, due to increasing the possibility of infection and accelerating rates of antimicrobial agents. It is recognized as a nosocomial pathogen due to its ability to form biofilms. These biofilms serve as a defensive barrier, increase antibiotic resistance, and make treatment more difficult. As a result, the current situation necessitates the rapid emergence of novel therapeutic approaches to ensure successful treatment outcomes. This review explores the intricate relationship between biofilm formation and antibiotic resistance in A. baumannii , emphasizing the role of key virulence factors and quorum sensing (QS) mechanisms that will lead to infections and facilitate insight into developing innovative method to control A. baumannii infections. Furthermore, the review article looks into promising approaches for preventing biofilm formation on medically important surfaces and potential therapeutic methods for eliminating preformed biofilms, which can address biofilm‐associated A. baumannii infections. Modern advances in emerging therapeutic options such as antimicrobial peptide (AMPs), nanoparticles (NPs), bacteriophage therapy, photodynamic therapy (PDT), and other biofilm inhibitors can assist readers understand the current landscape and future prospects for effectively treating A. baumannii biofilm infections.
The biogenic synthesis of metal nanoparticles (MNPs) by reducing metal ions with secondary metabolites of plant essential oils (EOs) is a one-step process that is also environmentally beneficial. This biogenic synthesis of metal nanoparticles is a relatively quick and simple procedure that may be carried out at low temperatures and pressures. Essential oils (EOs) are complex fats with a variety of constituents, some of which are volatile, organic, and physiologically active. They are widely used in a variety of industries, including the food, cosmetics, and medical sectors. Moreover, biosafety or ecologically friendly methods are used in the manufacturing of metal nanoparticles with EOs. Due to the overuse or underuse of antibiotics, a multidrug resistance problem has emerged all over the world. Antibiotic resistance has emerged in the majority of microorganisms, including bacteria, fungi, protozoans, and others, and this problem is now recognized as a global concern. (EOs) and metallic nanoparticles have antiseptic activity, making them a viable remedy for microbial resistance. Furthermore, essential oils have become a promising, effective and essential alternative in various areas of life.
Introduction
The rise in antibiotic resistant pathogens associated with bovine respiratory disease (BRD) poses a serious challenge, particularly to the beef feedlot industry, as they currently depend on antibiotics to prevent BRD to mitigate the financial burden (approx. $1 billion annual loss) inflicted by BRD-associated high mortality and morbidity in feedlot cattle. Thus, there is an impetus need for the development of antimicrobial alternative strategies against BRD. This study aimed to screen and select candidate essential oils (EOs) for the development of an intranasal EO spray that can inhibit BRD pathogens and promote microbiota-mediated respiratory health.
Methods
The effects of selected EOs (ajowan, cinnamon leaf, citronella, grapefruit, fennel, and thyme) on a bovine nasopharyngeal microbiota culture were evaluated using 16S rRNA gene sequencing. The microbiota culture was enriched by incubating nasopharyngeal swabs obtained from finishing beef heifers in brain heart infusion broth with and without EOs (0.025%, v/v). These EOs were then also evaluated for their immunomodulatory effects on bovine turbinate (BT) cells by analyzing the concentrations of 15 cytokines and chemokines in cell culture after 24 h incubation. The crystal violet assay was done to assess the antibiofilm activity of EOs against Escherichia coli UMN026 strain. Finally, 15 EOs were screened for their antiviral activity against the bovine viral diarrhea virus 1 (BVDV-1) using BT cells and a fluorescence-based method.
Results
Ajowan, fennel, and thyme resulted in a moderate reduction of overall nasopharyngeal microbiota growth with significant alterations of both alpha and beta diversity, and the relative abundance of predominant bacterial families (e.g., increasing Enterobacteriaceae and decreasing Moraxellaceae) compared to the control (p < 0.05). Co-incubation of BT cells with selected EOs resulted in minimal alterations in cytokine and chemokine levels (p > 0.05). Ajowan, thyme, fennel, and cinnamon leaf exhibited antibiofilm activity at concentrations of 0.025 and 0.05%. Reduction of BVDV-1 replication in BT cells was observed with thyme (strong), and ajowan and citronella (moderate) at 0.0125% concentration.
Discussion
Accordingly, ajowan, thyme, fennel, cinnamon leaf, and citronella EOs were selected for further development as an intranasal EO spray to prevent and control of BRD pathogens in feedlot cattle.
The absence of effective therapy against Escherichia coli O157:H7 infections has led to the need to develop new antimicrobial agents. As the use of synergistic combinations of natural antimicrobial compounds is growing as a new weapon in the fight against multidrug-resistant bacteria, here, we have tested new synergistic combinations of natural agents. Notably, we investigated a possible synergistic effect of combinations of essential oils and natural peptides to counteract the formation of biofilm. We chose three essential oils (i.e., Cymbopogon citratus, C. flexuosus and C. martinii) and one peptide already studied in our previous works. We determined the fractional inhibitory concentration (FIC) by analyzing the combination of the peptide derived from esculentin-1a, Esc(1–21), with the three essential oils. We also studied the effects of combinations by time–kill curves, scanning electron microscopy on biofilm and Sytox Green on cell membrane permeability. Finally, we analyzed the expression of different genes implicated in motility, biofilm formation and stress responses. The results showed a different pattern of gene expression in bacteria treated with the mixtures compared to those treated with the peptide or the single C. citratus essential oil. In conclusion, we demonstrated that the three essential oils used in combination with the peptide showed synergy against the E. coli O157:H7, proving attractive as an alternative strategy against E. coli pathogen infections.
Five essential oils (EOs) were previously characterized in vitro and identified as candidate EOs for the development of an intranasal EO spray to mitigate bovine respiratory disease (BRD) pathogens. In the present study, these EOs were evaluated for their potential to (i) reduce BRD pathogens, (ii) modulate nasopharyngeal microbiota, and (iii) influence animal performance, feeding behavior and immune response when a single dose administered intranasally to feedlot cattle. Forty beef steer calves (7–8 months old, Initial body weight = 284 ± 5 kg [SE]) received either an intranasal EO spray (ajowan, thyme, fennel, cinnamon leaf, and citronella) or PBS (Control; n = 20/group) on day 0. Deep nasopharyngeal swabs were collected on days (d) -1, 1, 2, 7, 14, 28, and 42 and processed for 16S rRNA gene sequencing, qPCR, and culturing. Significant effects of EO on community structure (d1), microbial richness and diversity, relative abundance of some dominant phyla (d1, d2, and d14), and the overall interaction network structure of the nasopharyngeal microbiota were detected. The relative abundance of Mannheimia was lower in the EO calves (4.34%) than in Control calves (10.4%) on d2, and M. haemolytica prevalence on d7 as compared to control calves. Feed intake, average daily gain, feeding behavior, and blood cell counts were not affected by EO treatment. Overall, a single intranasal dose of EO spray resulted in moderate modulation of nasopharyngeal microbiota and short-term inhibition of Mannheimia while not influencing animal performance, feeding behavior or immune response. Our study, for the first time, shows the potential use of intranasal EO to mitigate BRD in feedlot cattle.
Eucalyptus essential oil (EO) has significance economically since it is used in the medicinal and fragrance industries. The main objective of this study was to investigate the differences in yield, composition, antioxidant capacity, and antibacterial effectiveness of the EO extracted from Eucalyptus camaldulensis leaves. To achieve this, three distinct extraction techniques, namely steam distillation (SD), hydro distillation (HD), and superheated steam distillation (SHSD), were utilized to isolate the EO. The study aimed to analyze and compare these parameters among the three extraction methods. Based on the findings from the experiments, it has been found that using SHSD resulted in a higher EO yield than conventional techniques, and this SHSD produced a greater amount of EO in a shorter time. The EOs extracted using all three techniques have 1,8 cineole as the main constituent, according to gas chromatography-mass spectrometry (GC-MS) analysis results. All of the EOs demonstrated significant antioxidant capacities when tested in vitro using a variety of antioxidant assays. The EOs extracted through HD showed greater antibacterial activity among the other extraction processes, as evaluated by agar well diffusion and resazurin microtitre-plate assays. In conclusion, SHSD is more efficient for extracting EOs and antioxidant activity than traditional HD and SD.
Background
Acinetobacter baumannii ( A. baumannii ) is an opportunistic pathogen that poses dangerous health threat. It is a main cause of biofilm-associated infections that are mostly resistant to antibiotic therapy. Because of its capacity to form biofilm on biotic and abiotic surfaces, it has been linked to most nosocomial infections such as ventilator-associated pneumonia, urinary tract infections, bacteremia, meningitis, wound infections, soft tissue infections, and peritonitis.
Main body of the abstract
The biofilm refers to an organized group of microbial cells that are embedded in an exopolymeric substance made of protein, extracellular DNA, and polysaccharide. Bacterial cells in biofilms are resistant to chemicals, phagocytosis, and other elements of the body’s innate and acquired immune systems posing treatment challenges. Biofilm formation in A. baumannii is a complicated process that is influenced by a variety of factors such as outer membrane protein A, poly-β-(1,6)- N acetyl glucosamine (PAGE), biofilm-associated protein, two-component system (Bfm/S BfmR), chaperone–usher (Csu) pilus assembly system of pili, BlaPER-1 belonging to β-lactamase family, extracellular polymeric substance, and the quorum sensing system. Several biofilm-associated genes influence antimicrobial susceptibility, implying a link between biofilm formation and antimicrobial resistance.
Short conclusion
This review describes the complex biofilm system of A. baumannii , which gives it a survival advantage and increases its colonization ability. Also, it demonstrates various extrinsic and intrinsic factors that function and regulate the biofilm machinery of A. baumannii . Furthermore, this study considers prospective ways for preventing biofilm development on relevant medical equipment, as well as potential therapeutic strategies for eradicating mature biofilms, which can aid in the treatment of biofilm-associated A. baumannii infection.
Medicinal plants exerted their antibacterial effects through many mechanisms included inhibition of cell wall synthesis, inhibition of cell membrane synthesis, disruption of cytoplasmic membrane, inhibition of bacterial proteins synthesis, inhibition of nucleic acid synthesis, inhibition of energy metabolism, as well as inhibition of bacterial virulence factors. The current review highlighted the medicinal plants with antibacterial activity with their spectrum of action.
Medicinal plants exerted their antibacterial effects through many mechanisms included inhibition of cell wall synthesis, inhibition of cell membrane synthesis, disruption of cytoplasmic membrane, inhibition of bacterial proteins synthesis, inhibition of nucleic acid synthesis, inhibition of energy metabolism, as well as inhibition of bacterial virulence factors. The current review highlighted the medicinal plants with antibacterial activity with their spectrum of action.
Nowadays, the exclusive use of commercial anthelmintics for the treatment of gastrointestinal nematode infections in ruminants is less sustainable due to anthelmintic resistance, as well as the problem of drug residues in animal products and the environment. Therefore, an integrated therapeutic approach is needed, including the search for alternatives to synthetic anthelmintic drugs. The aim of this study was to evaluate the possibility of using the essential oil of peppermint (Mentha x piperita L.) in the control of gastrointestinal nematodes in sheep. For this purpose, the in vitro and in vivo anthelmintic efficacy of this oil and the toxic effects on the hosts were examined. In the in vitro egg hatch test, ovicidal activity varied from 21.0–90.3% depending on the concentration of essential oil used (0.0125, 0.025, 0.049, 0.195, 0.781, 3.125, 12.5, and 50 mg/mL). To some extent, anthelmintic efficacy was confirmed in the in vivo fecal egg count reduction test at a mean dose of 150 mg/kg, with an average reduction of nematode eggs of 26.9 and 46.0% at Days 7 and 14 after treatment, respectively. Furthermore, no toxic effects of applied oil were observed on sheep behavior, kidney, or liver function. The main compounds identified by gas chromatography–mass spectrometry analyzes were menthol (32.6%), menthone (22.0%), menthyl-acetate (10.0%), and isomenthone (9.39%). Due to their complex chemical compositions, numerous bioactive ingredients, and natural origin, herbal formulations represent a potentially valuable alternative for the control of gastrointestinal nematodes in sheep. In this context, the results of the present study showed that peppermint essential oil is one of the promising candidates. Further studies should be performed to collect more data on the safety profile of M. piperita EO in treated animals to find the most appropriate formulation for use in field conditions and to test it against resistant gastrointestinal nematode populations.
The application of traditional medicine in global health care is increasing, particularly against the threat of emerging, reemerging, drug-resistant, and difficult-to-treat infections. Common antibiotics, although useful, have adverse effects or are ineffective against many infections. Also, many emerging or reemerging infections lack proper therapeutics. To face this global threat, alternative or new drugs are urgently required. The secondary metabolites of plants are the vital components of nature that help in human defense by interfering with specific molecules of microbial or human cells, modulating the cell signaling pathways, and protecting against UV damage and oxidative stress. Hence, “plant-derived antimicrobials” or “phyto-antimicrobials” can predispose inhibitory activity against diverse viruses, bacteria, and fungi to parasites. It not only causes leakage of the microbial cell wall, damage to the cell membrane, or cell lysis, but also inactivate/disrupt proteins or enzymes and interfere transcription to translation leading to the death of the microbes. Hence, natural antimicrobials may be the most ideal for health care, as it can help in healing process and kill/inhibit the pathogens efficiently and may prevent the development of drug resistance. Billions of living species on the earth from bacteria to animals produce a plethora of healing chemicals, many of which are still unknown. Thus, the present review portrays the antimicrobial role of selected traditional medicine(s) including their active compounds with the possible mechanism of action for managing difficult-to-treat infections.
The aim of current work was to determine essential oils (EOs) composition from three Eucalyptus species, including E. citriodora, E. camaldulensis and E. globulus and assess their α-glucosidase inhibitory activity. The EOs were collected using the hydrodistillation technique and characterized by GC/MS, GC-FID and NMR. The isolated EOs from leaves parts of Eucalyptus species varied from 0.56 to 1.0% on fresh weight basis. The content of the EOs was distinct according to the species. The most abundant metabolites were identified as citronellal (0-83.0%), 1,8-cineole (0.2-44.8%), spathulenol (0.4-16.1%) α-pinene (0.4-15.9%), p-cymene (3.7-11.9%), citronellol (0-8.6%), β-eudesmol (5.3-8.6%) and β-pinene (0-7.1%). The EOs obtained from targeted samples exhibited strong α-glucosidase inhibitory activity. These results are encouraging and underline that the EOs of Eucalyptus species may be a promising alternative source of natural antidiabetic.
Eucalypt is the vernacular name used to refer to trees of the three genera, Angophora Cav., Corymbia K. D. Hill & L.A.S. Johnson and Eucalyptus L’Herit. These closely related genera are within the Myrtaceae family and include around 1000 taxa in total, nearly all of which are indigenous to Australia. In China, over 5 million ha of industrial plantations have been established with selected eucalypt taxa. However, there are no plantations in this country managed specifically for the purpose of eucalypt leaf oil production. Even so, for many years China has been the world’s largest producer of crude eucalypt oil distilled from eucalypt leaves. These leaves are mainly collected from community plantings, mostly of E. globulus and E. smithii. A project was carried out on species selection for leaf oil production in late 1990’s in southwestern China, and included testing of the species E. radiata, E. bakeri, E. polybractea and others. Eucalypt oils are used as raw materials in perfumery, cosmetics, food and beverage industries as well as in various aromatherapy and physiotherapy treatments. The 1,8-cineole (eucalyptol) compound is the principal and the most important constituent of the most eucalypt leaf oils, and this has demonstrated antimicrobial and anti-inflammatory activities. Such uses of eucalypt essential oils for human health as well as for environment improvement have been well established by scientific research in many countries, with such oils having a long history of medicinal use in Australia and Europe. Even so, there is a need to investigate the prime effects of such essential oils and their possible efficacy in the treatment of a greater number of pathological conditions in China. It is also advocated that the country’s existing eucalypt plantations be more widely used as places for ‘forest bathing’ and such nature-based well-being practices; and that investigations be taken into the use of eucalypt leaf oils to improve hygiene and fight diseases, such as that caused by the virus.
Eucalyptus camaldulensis Dehnh. is regarded to possess various medicinal properties such as anesthetic, antiseptic, astringent and anti diabetic, but there are few studies on its antibacterial effects. In the present study antibacterial activity of E. camaldulensis on 100 Multi Drug Resistant isolates of S. aureus, A. baumannii, P. aeruginosa, K. pneumoniae and E. coli were evaluated. E. camaldulensis samples were collected from the fields of Urmia in Northwestern Iran. Plants were cut, and powder was prepared. Powdered plants were extracted by maceration at room temperature for 72 hours. Bacterial isolates were collected from clinical specimens of different wards of educational hospitals in Urmia, Iran during a 12-month period. The susceptibility of isolates to E. camaldulensis extracts was determined using a broth microdilution method. Considering to the wide application of ciprofloxacin in treatment of bacterial nosocomial infections, the antibacterial effects of ciprofloxacin on isolates was also determined. All the multi-drug resistant bacterial isolates were sensitive to different concentrations of E. camaldulensis hydro-alcoholic extract. The most sensitive bacterial isolates to E. camaldulensis extracts were P. aeruginosa isolates, although 69% of isolates were resistant to ciprofloxacin. Results demonstrated that this herbal drug may represent a new source of antimicrobial agent for controlling the hospital acquired infections. However, studies that are more adequate must be carried out to verify the possibility of using it for fighting these bacteria in human infections.
Rosa damascena petals were extracted by water, hexane and ethanol. The latter was further fractionated with chloroform, ethyl acetate and butanol. Rose oil and different petal extracts were evaluated against three fungi and eleven Gram-positive, Gram-negative and acid-fast bacteria. Rose oil and all extracts exerted broad spectrum antimicrobial activities against the tested organisms. The descending order of antifungal activity of rose oil and different extracts was, Penicillium notatum, Aspergillus niger and Candida albicans. Ethyl acetate extracted fraction was relatively more active against the tested bacteria than the other tested extracts. Gram-positive bacteria, Staphylococcus aureus, Bacillus subtilis and Streptococcus pyogenes were more sensitive than Gram-negative bacteria and had MICs and MBCs in the range of 0.125 to 2 mg/ml and 0.5 to 4 mg/ml respectively. Acinetobacter baumannii, which is intrinsically resistant to most antibiotics, was relatively more sensitive than other Gram-negative bacteria. On the contrary, Klebsiella pneumoniae was the least sensitive Gram-negative bacterium. The MICs of Gram-positive bacteria to different extracts were significantly (p≤0.05) less than those of K. pneumoniae. The acid-fast bacterium, Mycobacterium phlei, was intermediate in its sensitivity to the extracted fractions compared to Gram-positive and Gram-negative bacteria. The antibacterial activity of aqueous extracts of petals suggests a possible utilization of rose petal boiling water after rose oil distillation. Further studies are required to separate and identify the active antimicrobial phytoconstituents of petals to utilize them pharmaceutically.
Adams, R. P. 2007. Identification of essential oil components by gas chromatography/ mass spectrometry, 4th Edition. Allured Publ., Carol Stream, IL
Is out of print, but you can obtain a free pdf of it at
www.juniperus.org
Acinetobacter sp. represent an important cause of nosocomial infections. Their resistance to some antibiotics, their ability to survive on inanimate surfaces in the hospital environment and their ability to produce biofilms contributes to their virulence. The aim of the study was to determine the antibacterial properties of cinnamon, lavender and geranium essential oils against bacteria of the genus Acinetobacter isolated from several clinical materials and from the hospital environment. A comprehensive evaluation of the susceptibility of Acinetobacter sp. clinical strains to recommended antibiotics was performed. The constituents of cinnamon, lavender and geranium essential oils were identified by GC-FID-MS analysis, and their Minimal Inhibitory Concentrations (MICs) against tested clinical strains were determined by the micro-dilution broth method. In addition, the effects of essential oils on the viability of human microvascular endothelial cells (HMEC-1) and glioblastoma cell line (T98G) were evaluated. Cinnamon bark oil was the most active against clinical and environmental strains of Acinetobacter baumannii with MIC values ranging from 0.5 to 2.5 µL/mL. The MIC values for geranium oil were between 7.5 and 9.5 µL/mL, and between 10.5 and 13.0 µL/mL for lavender oil. These essential oils can be best employed in the fight against infections caused by bacteria from Acinetobacter genus as components of formulations for hygiene and disinfection of hospital environment.
For many years, the battle between humans and the multitudes of infection and disease causing pathogens continues. Emerging at the battlefield as some of the most significant challenges to human health are bacterial resistance and its rapid rise. These have become a major concern in global public health invigorating the need for new antimicrobial compounds. A rational approach to deal with antibiotic resistance problems requires detailed knowledge of the different biological and non-biological factors that affect the rate and extent of resistance development. Combination therapy combining conventional antibiotics and essential oils is currently blooming and represents a potential area for future investigations. This new generation of phytopharmaceuticals may shed light on the development of new pharmacological regimes in combating antibiotic resistance. This review consolidated and described the observed synergistic outcome between essential oils and antibiotics, and highlighted the possibilities of essential oils as the potential resistance modifying agent.
Background
Traditional medicine has remained as the most affordable and easily accessible source of treatment in the primary healthcare system of resource poor communities in Zimbabwe. The local people have a long history of traditional plant usage for medicinal purposes. Despite the increasing acceptance of traditional medicine in Zimbabwe, this rich indigenous knowledge is not adequately documented. Documentation of plants used as traditional medicines is needed so that the knowledge can be preserved and the utilized plants conserved and used sustainably. The primary objective of this paper is to summarize information on traditional uses of medicinal plants in south-central Zimbabwe, identifying research gaps and suggesting perspectives for future research.
Methods
This study is based on a review of the literature published in scientific journals, books, reports from national, regional and international organizations, theses, conference papers and other grey materials.
Results
A total of 93 medicinal plant species representing 41 families and 77 genera are used in south-central Zimbabwe. These plant species are used to treat 18 diseases and disorder categories, with the highest number of species used for gastro-intestinal disorders, followed by sexually transmitted infections, cold, cough and sore throat and gynaecological problems. Shrubs and trees (38% each) were the primary sources of medicinal plants, followed by herbs (21%) and climbers (3%). The therapeutic claims made on medicinal plants documented in south-central Zimbabwe are well supported by literature, with 82.8% of the plant species having similar applications in other regions of Zimbabwe as well as other parts of the world and 89.2% having documented biological and pharmacological properties.
Conclusion
This study illustrates the importance of traditional medicines in the treatment and management of human diseases and ailments in south-central Zimbabwe. Traditional medicines still play an important role in meeting basic health care of local communities in Zimbabwe.
The mechanism of antimicrobial activity of essential oils components; �- terpineol, g-terpinene and
eugenol was studied to evaluate their effect on the bacterial membrane against four strains of bacteria:
Listeria monocytogenes, Streptococcus pyogenes, Proteus vulgaris and Escherichia coli. The study
was done to observe changes in membrane composition by assaying for the leakage of protein and lipid
using Bradford and van Handel’s method respectively. The oils components were capable of inducing
cell lysis by the leakage of protein and lipid contents. Eugenol at 2 × MIC was highly effective toward
protein content leakage after 120 min of exposure. Alpha terpineol and g-terpinene showed similar effect
at 2 × MIC under the same condition. Gamma terpinene displayed the highest activity toward lipid
content leakage at 2 x MIC while �-terpineol and eugenol showed similar effect after 120 min of
exposure. The result revealed that both cell wall and membrane of the treated gram negative and gram
positive bacteria were significantly damaged.
Abstract With the increase in antibiotic-resistant bacteria and the lack of new antibiotics being brought onto the market, alternative strategies need to be found to cope with infections resulting from drug-resistant bacteria. A possible solution may be to combine existing antibiotics with phytochemicals to enhance the efficacy of antibiotics. A group of phytochemicals that is said to have such effects, according to in vitro studies, is essential oils (EOs) and their components. Amongst others, EOs containing carvacrol, cinnamaldehyde, cinnamic acid, eugenol and thymol can have a synergistic effect in combination with antibiotics. Several modes of action have been put forward by which antibiotics and the essential oil components may act synergistically, such as by affecting multiple targets; by physicochemical interactions and inhibiting antibacterial-resistance mechanisms. Many reported assays show additivity or moderate synergism, indicating that EOs may offer possibilities for reducing antibiotic use.
Water-distilled oil from the dried leaves of two trees of Eucalyptus camaldulensis Dehn. of different ages, were analyzed by GC/MS. The principal constituent, in the 4-year-old tree oil and the 11-year-old tree oil, was 1,8-cineole (40.0%, 37.1%, respectively). Other major constituents were: β-pinene (9.2%, 0.1%), γ-terpinene (5.3%,10.4%), p-cymene (4.7%, 11.6%), terpinen-4-ol (2.8%, 5.5%) and globulol (5.4%, 9.6%).
The chemical composition of essential oils from 22 Eucalyptus species growing in Uruguay are described. It was found that 1, 8-cineole, citronellal, p-cymene and benzaldehyde are the main constituents.
A simple bioautographic agar overlay assay using Candida albicans as the indicator organism for the detection and activity-guided fractionation of antifungal compounds by thin layer chromatography has been developed. Inhibition of fungal growth was assessed by the detection of dehydrogenase activity with thiazolyl blue (methylthiazolyltetrazolium chloride; MTT). A series of clinically used antimycotic agents were tested in order to determine the sensitivity of the assay. The compatibility of the agar overlay technique with chemically modified silica gel (Diol and RP-18) plates and with various organic solvents was evaluated. The methodology is also applicable to the search for antibacterial compounds, as shown with Bacillus subtilis as a test organism.
In 1957, Tunisia introduced 117 species of Eucalyptus; they have been used as fire wood, for the production of mine wood and to fight erosion. Actually, Eucalyptus essential oil is traditionally used to treat respiratory tract disorders such as pharyngitis, bronchitis, and sinusitis. A few investigations were reported on the biological activities of Eucalyptus oils worldwide. In Tunisia, our previous works conducted in 2010 and 2011 had been the first reports to study the antibacterial activities against reference strains. At that time it was not possible to evaluate their antimicrobial activities against clinical bacterial strains and other pathogens such as virus and fungi.
The essential oils of eight Eucalyptus species harvested from the Jbel Abderrahman, Korbous (North East Tunisia) and Souinet arboreta (North of Tunisia) were evaluated for their antimicrobial activities by disc diffusion and microbroth dilution methods against seven bacterial isolates: Haemophilus influenzae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae and Streptococcus pyogenes. In addition, the bactericidal, fungicidal and the antiviral activities of the tested oils were carried out.
Twenty five components were identified by GC/FID and GC/MS. These components were used to correlate with the biological activities of the tested oils. The chemical principal component analysis identified three groups, each of them constituted a chemotype. According to the values of zone diameter and percentage of the inhibition (zdi, % I, respectively), four groups and subgroups of bacterial strains and three groups of fungal strains were characterized by their sensitivity levels to Eucalyptus oils. The cytotoxic effect and the antiviral activity varied significantly within Eucalyptus species oils.
E. odorata showed the strongest activity against S. aureus, H. influenzae, S. agalactiae, S. pyogenes, S. pneumoniae and against all the tested fungal strains. In addition, E. odorata oil showed the most cytotoxic effect. However, the best antiviral activity appeared with E. bicostata. Virus pretreatment with E. bicostata essential oil showed better antiviral activity (IC50 = 0.7 mg/ml, SI = 22.8) than cell-pretreatment (IC50 = 4.8 mg/ml, SI = 3.33). The essential oil of E. astringens showed antiviral activity only when incubated with virus prior to cell infection. This activity was dose-dependent and the antiviral activity diminished with the decreasing essential oil concentration.
The genus Acinetobacter has gained importance in recent years due to involvement in serious infections and antimicrobial resistance. Many plants have been evaluated not only for direct antimicrobial activity, but also as resistance modifying agents. The Essential oil of Citrus limon (EOCL) addition at 156.25 µgmL(-1) (MIC/8) sub-inhibitory concentration in the growth medium led to MIC decrease for amikacin, imipenem and meropenem. The Essential oil of Cinnamomum zeylanicum (EOCZ) addition at 78.125 µg mL(-1) (MIC/8) sub-inhibitory concentrations in the growth medium caused drastic MIC reduction of amikacin. Results of combining antibiotics and essential oils had shown us a synergistic effect with both essential oils/amikacin combinations. An additive effect was observed with the combinations of both essential oils and gentamicin. The results of this study suggest that essential oil of C. limon and C. zeylanicum may suppress the growth of Acinetobacter species and could be a source of metabolites with antibacterial modifying activity.
Eucalyptus globulus Labill (Myrtaceae) is the principal source of eucalyptus oil in the world and has been used as an antiseptic and for relieving symptoms of cough, cold, sore throat, and other infections. The oil, well known as 'eucalyptus oil' commercially, has been produced from the leaves. Biological properties of the essential oil of fruits from E. globulus have not been investigated much.
The present study was performed to examine the antimicrobial activity of the fruit oil of E. globulus (EGF) and the leaf oils of E. globulus (EGL), E. radiata Sieber ex DC (ERL) and E. citriodora Hook (ECL) against multidrug-resistant (MDR) bacteria. Furthermore, this study was attempted to characterize the oils as well as to establish a relationship between the chemical composition and the corresponding antimicrobial properties.
The chemical composition of the oils was analyzed by GLC-MS. The oils and isolated major components of the oils were tested against MDR bacteria using the broth microdilution method.
EGF exerted the most pronounced activity against methicillin-resistant Staphylococcus aureus (MIC ~ 250 µg/ml). EGF mainly consisted of aromadendrene (31.17%), whereas ECL had citronellal (90.07%) and citronellol (4.32%) as the major compounds. 1,8-cineole was most abundant in EGL (86.51%) and ERL (82.66%).
The activity of the oils can be ranked as EGF > ECL > ERL ~ EGL. However, all the oils and the components were hardly active against MDR Gram-negative bacteria. Aromadendrene was found to be the most active, followed by citronellol, citronellal and 1,8-cineole.
The crude extracts of Eucalyptus camaldulensis were investigated for their in vitro antimicrobial and gastro-protective activities in albino rats. The antimicrobial activity was investigated by screening the crude plant extract for activity against Candida albicans and clinically isolated gentamycin resistant wound bacteria viz: Staphylococcus aureus UCH 2600, Escherichia coli UCH 2554, Pseudomonas aeruginosa UCH 2780 and Proteus mirabilis UCH 2773. These microorganisms were susceptible to the crude extracts at a 10 mg mL-1 concentration. The gastroprotective activity of the methanol extract of Eucalyptus camaldulensis (MEEC) was investigated in rats. Gastro protection was evaluated against gastric mucosal damage induced by ethanol/HCl mixture. The Hcl/Ethanol mixture (1.5 mL of 0.15 N HCl in 70% ethanol) caused severe gastric damage with ulcer index 2.7�0.33. Pre-treatment of animals with crude extract of Eucalyptus camaldulensis leaf 200 and 1000 mg kg-1 orally for 1 h significantly reduced the formation of ulcer by the HCl/ethanol mixture with preventive ratios of 56 and 89%, respectively. Ranitidine afforded 92.5% protection. The results suggest that crude extracts of Eucalyptus camaldulensis has both antimicrobial and anti-ulcer properties.
The aim of the present study was to investigate the chemical composition of the essential oil of the fruits of Eucalyptus globulus and to examine the potential application of the fruit oil against multidrug-resistant bacteria. GLC/MS analysis in the fruit oil showed that aromadendrene was the main compound followed by 1,8-cineole and globulol. The three most abundant components of the fruit oil were also tested individually against microorganisms. In addition, the synergistic effects of combinations of the major constituents (aromadendrene and 1,8-cineole) of the fruit oil were also investigated. All Gram-positive bacteria were susceptible to the fruit oil with different degrees of susceptibility as determined by microdilution method. The oil exerted a marked inhibition against multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) Enterococcus faecalis. The results indicated that aromadendrene might be responsible for the antimicrobial properties, whereas 1,8-cineole and globulol exhibited low activities. The checkerboard assay demonstrated that combinations of 1,8-cineole and aromadendrene reduce the MIC in most cases in an additive way, whereas the time-kill assay indicates a synergistic effect.
The aim of this study was to verify the existence of synergistic antibacterial effect between four essential oils (Aniba rosaeodora, Melaleuca alternifolia, Origanum vulgare, and Pelargonium graveolens) individually combined with the antibacterial drug Gentamicin. We investigated the effectiveness in vitro of the association of essential oil/Gentamicin, against fifteen different strains of Gram positive and Gram negative bacteria. The antibacterial effects of these oils in combination with Gentamicin were evaluated by using the MHB microdilution method, while gas chromatography (GC) and GC/Mass spectrometry were used to analyze the chemical composition of the oils. A synergistic interaction was observed against all tested strains with the associations between the essential oils Aniba rosaeodora/Gentamicin and Pelargonium graveolens/Gentamicin. In particular a very strong synergistic interaction was observed against Acinetobacter baumannii ATCC 19606 (FIC index = 0.11). In contrast, the essential oils Origanum vulgare and Melaleuca alternifolia in association with Gentamicin were less effective on bacterial species growth. In vitro interaction can improve the antimicrobial effectiveness of the Gentamicin and may contribute to reduce its dose correlated to side effects.
Effective disinfection and antisepsis is pivotal in preventing infections within the healthcare setting. Chlorhexidine digluconate (CHG) is a widely used disinfectant/antiseptic possessing broad-spectrum antimicrobial activity; however, its penetration into bacterial biofilms and human skin is poor. The aim of this study was to investigate the antimicrobial efficacy of crude eucalyptus oil (EO) and its main component 1,8-cineole (a recognized permeation enhancer), alone and in combination with CHG, against a panel of clinically relevant microorganisms grown in planktonic and biofilm cultures.
MICs and minimum bactericidal/fungicidal concentrations were determined for each microorganism grown in suspension and biofilm using microbroth dilution and ATP bioluminescence, respectively. Chequerboard assays were used to determine synergistic, indifferent or antagonistic interactions between CHG and EO or 1,8-cineole.
Antimicrobial activity was demonstrated by CHG, EO and 1,8-cineole; however, CHG was significantly more active against microorganisms in both planktonic and biofilm modes of growth (P < 0.05). Crude EO was significantly more efficacious against microorganisms grown in suspension compared with 1,8-cineole (P < 0.05). Synergistic activity was demonstrated between CHG and both EO and 1,8-cineole against suspensions of Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli and Candida albicans, and biofilm cultures of MRSA and Pseudomonas aeruginosa.
In conclusion, CHG may be combined with either crude EO or its major component 1,8-cineole for enhanced, synergistic antimicrobial activity against a wide range of microorganisms in planktonic and biofilm modes of growth; however, the superior antimicrobial efficacy associated with crude EO alone, compared with 1,8-cineole, favours its combination with CHG.
Pseudomonas aeruginosa is an important opportunistic pathogen causing widespread infections by numerous virulence factors. Increasing resistance to antibiotics makes the Pseudomonas infections treatment further difficult. The purpose of this study was to evaluate antimicrobial characteristics of essential oils from Matricaria chamomilla, Artemisia persica, Zataria multiflora, Myrtus communis, Ruta graveolens, Eucalyptus camaldulensis and Ferulagummosa on Pseudomonas aeruginosa (ATCC 27853). The selected essential oils were screened against P. aeruginosa using the disc diffusion method. The minimal inhibitory and bactericidal concentrations (MIC and MBC) of the active essential oils were tested using macrodilution method at concentrations ranging from0.125 to 256 μg/ml. It was found by GC/MS analyses that Z. multiflora, M. communis and E. camaldulensis possess the most potent oils. Three of the seven essential oils (Z. multiflora, M. communis and E. camaldulensis) were significantly active against P. aeruginosa exhibiting MIC/MBC of 64/128, 64/64 and 64/128 µg/ml, respectively. Gas chromatography mass spectrometry (GC/MS) analysis led to identification of 32, 21 and 22 components in M. communis, E. camaldulensis and Z. multiflora oils, respectively. With a view to antibacterial activity of some oils against the tested bacterium, their safe antibacterial potentials can therefore be exploited as alternative agents in combating infections of P. aeruginosa origin.
The chemical composition of the essential oils obtained from the aerial parts of Helichrysum cymosum and H. fulgidum, from Tanzania, were analyzed by GC and GC/MS. A total of sixty-five compounds, representing 92.4% and 88.2% of the two oils, respectively, were identified. trans-Caryophyllene, caryophyllene oxide, beta-pinene, p-cymene, spathulenol and beta-bourbonene were found to be the main components. Furthermore, the oils were tested against six gram (+/-) bacteria and three pathogenic fungi. It was found that the oil of H. fulgidum exhibited significant antimicrobial activity, while the oil of H. cymosum was not active at all.
The natural antimicrobial compound carvacrol shows a high preference for hydrophobic phases. The partition coefficients of
carvacrol in both octanol-water and liposome-buffer phases were determined (3.64 and 3.26, respectively). Addition of carvacrol
to a liposomal suspension resulted in an expansion of the liposomal membrane. Maximum expansion was observed after the addition
of 0.50 μmol of carvacrol/mg of l-α-phosphatidylethanolamine. Cymene, a biological precursor of carvacrol which lacks a hydroxyl group, was found to have a
higher preference for liposomal membranes, thereby causing more expansion. The effect of cymene on the membrane potential
was less pronounced than the effect of carvacrol. The pH gradient and ATP pools were not affected by cymene. Measurement of
the antimicrobial activities of compounds similar to carvacrol (e.g., thymol, cymene, menthol, and carvacrol methyl ester)
showed that the hydroxyl group of this compound and the presence of a system of delocalized electrons are important for the
antimicrobial activity of carvacrol. Based on this study, we hypothesize that carvacrol destabilizes the cytoplasmic membrane
and, in addition, acts as a proton exchanger, thereby reducing the pH gradient across the cytoplasmic membrane. The resulting
collapse of the proton motive force and depletion of the ATP pool eventually lead to cell death.
In the present paper, we report the antimicrobial efficacy of three monoterpenes [linalyl acetate, (+)menthol, and thymol] against the gram-positive bacterium Staphylococcus aureus and the gram-negative bacterium Escherichia coli. For a better understanding of their mechanisms of action, the capability of these three monoterpenes to damage biomembranes was evaluated by monitoring the release, following exposure to the compounds under study, of the water-soluble fluorescent marker carboxyfluorescein from unilamellar vesicles with different lipidic compositions (phosphatidylcholine, phosphatidylcholine/phosphatidylserine [9:1], phosphatidylcholine/stearylamine [9:1], and phosphatidylglycerol/cardiolipin [9:1]). Furthermore, the interaction of the terpenes tested with dimyristoylphosphatidylcholine multilamellar vesicles as model membranes was monitored by means of differential scanning calorimetry. Finally, the results were related to the relative lipophilicity and water solubility of the compounds examined. Taken together, our findings lead us to speculate that the antimicrobial effect of (+)menthol, thymol, and linalyl acetate may result, at least partially, from a perturbation of the lipid fraction of microorganism plasma membrane, resulting in alterations of membrane permeability and in leakage of intracellular materials. Besides being related to physicochemical characteristics of the drugs (such as lipophilicity and water solubility), this effect seems to be dependent on lipid composition and net surface charge of microbial membranes. Furthermore, the drugs might cross the cell membranes, penetrating into the interior of the cell and interacting with intracellular sites critical for antibacterial activity.
Acinetobacter baumannii is a species of nonfermentative gram-negative bacteria commonly found in water and soil. This organism was susceptible to most antibiotics in the 1970s. It has now become a major cause of hospital-acquired infections worldwide due to its remarkable propensity to rapidly acquire resistance determinants to a wide range of antibacterial agents. Here we use a comparative genomic approach to identify the complete repertoire of resistance genes exhibited by the multidrug-resistant A. baumannii strain AYE, which is epidemic in France, as well as to investigate the mechanisms of their acquisition by comparison with the fully susceptible A. baumannii strain SDF, which is associated with human body lice. The assembly of the whole shotgun genome sequences of the strains AYE and SDF gave an estimated size of 3.9 and 3.2 Mb, respectively. A. baumannii strain AYE exhibits an 86-kb genomic region termed a resistance island--the largest identified to date--in which 45 resistance genes are clustered. At the homologous location, the SDF strain exhibits a 20 kb-genomic island flanked by transposases but devoid of resistance markers. Such a switching genomic structure might be a hotspot that could explain the rapid acquisition of resistance markers under antimicrobial pressure. Sequence similarity and phylogenetic analyses confirm that most of the resistance genes found in the A. baumannii strain AYE have been recently acquired from bacteria of the genera Pseudomonas, Salmonella, or Escherichia. This study also resulted in the discovery of 19 new putative resistance genes. Whole-genome sequencing appears to be a fast and efficient approach to the exhaustive identification of resistance genes in epidemic infectious agents of clinical significance.
The Antimicrobial Availability Task Force (AATF) of the Infectious Diseases Society of America (IDSA) has viewed with concern
the decreasing investment by major pharmaceutical companies in antimicrobial research and development. Although smaller companies
are stepping forward to address this gap, their success is uncertain. The IDSA proposed legislative and other federal solutions
to this emerging public health problem in its July 2004 policy report “Bad Bugs, No Drugs: As Antibiotic R&D Stagnates, a
Public Health Crisis Brews.” At this time, the legislative response cannot be predicted. To emphasize further the urgency
of the problem for the benefit of legislators and policy makers and to capture the ongoing frustration our clinician colleagues
experience in their frequent return to an inadequate medicine cabinet, the AATF has prepared this review to highlight pathogens
that are frequently resistant to licensed antimicrobials and for which few, if any, potentially effective drugs are identifiable
in the late-stage development pipeline.
The antimicrobial activity of three Salvia species, i.e. S. santolinifolia, S. hydrangea and S. mirzayanii, essential oils were investigated. The essential oils were obtained from the aerial parts of plants and analyzed by GC-MS. The main constituents of aforementioned species were alpha-pinene (72.4%), beta-pinene (6.6%) and limonene (5.3%); beta-caryophyllene (25.1%), 1,8-cineol (15.2%) and caryophyllene oxide (11.5%); alpha-terpinenyl acetate (22.6%), 1,8-cineol (21.2%) and linalool (8.9%), respectively. Bioassays exhibited that the property of the oil of S. myrzayanii was superior to others. The antimicrobial activity of essential oil from Salvia species may well be due to the presence of synergy between six tested compounds (linalool, 1,8-cineol, alpha-pinene, beta-pinene, beta-caryophyllene and limonene) and other constituents of the oils with various degrees of antimicrobial activity. Among these, linalool and 1,8-cineol had the highest antimicrobial activity.