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Escherichia coli and Staphylococcus aureus most common source of infection
Abstract
Escherichia coli and Staphylococcus aureus are a serious cause of a variety of community-and hospital-acquired infections. E. coli is one of the most common nosocomial pathogens that cause urinary tract infections (UTIs) and enterocolitis. S. aureus is also an etiological infection agent responsible for significant levels of morbidity and mortality. According to Broad Institute. (2010), Escherichia coli accounts for 17.3% of clinical infections requiring hospitalization and is the second most common source of infection behind Staphylococcus aureus (18.8%). In recent years, the emergence of resistant Staphylococcus aureus and resistant Escherichia coli strains to many antibiotics has been observed worldwide. These have become a major concern in global public health invigorating the need for new antimicrobial compounds. This review described these two bacteria, their taxonomies, morphology and biochemical characteristics, habitat and growth characteristics, the caused infections, their treatment and resistances to antibiotics.
... Human pathogenic bacteria, such as Escherichia coli, can cause neonatal meningitis; Staphylococcus aureus can cause foodborne illnesses like endocarditis; and Salmonella enterica sp. can cause localized infections like gastroenteritis [39][40][41][42]. P. vulgaris is the primary cause of urinary tract infections (UTIs), which are a major risk factor for infections in the community and hospital [43]. ...
Medical professionals have used synthetic medicine to treat bacterial infections. Scientists globally have been on the search for the utilization of natural plant products as alternatives. Therefore, this study investigated the preliminary phytochemical screening, and characterization of bioactive compounds and anti-bacterial properties of Eupatorium odoratum. Phytochemicals were detected using standard methods, certain bioactive compounds were detected using thin layer chromatographic (TLC) technique, ultraviolet (UV) visible and Fourier transform infra-red (FTIR) spectroscopic techniques. Antimicrobial screening was carried out using the punched agar diffusion method, the minimum inhibitory concentration and minimum bactericidal concentration of test organisms were determined by using serial doubling dilution method. Saponins, tannins, glycosides, alkaloids, steroids, terpenoids, proteins, oil were detected in the crude extract and some bioactive compounds which denoted the presence of various phytochemicals were found in the three solvent extracts used. All extracts showed good antibacterial activities with zone inhibition of 15-25 mm against all microorganism specimens; however, the chloroform extract was more potent in causing inhibition with Staphylococcus aureus (25 mm), having the highest zone of inhibition. Eupatorium odoratum can therefore be utilized as an alternative medicinal agent against a variety of bacterial infections. License: CC BY 4.0 Open Access article.
... The yoghurts samples were also analysed regarding their antibacterial capacity, to evaluate their possibility to inhibit the growth of bacteria. This biological capacity was assessed against S. aureus and E. coli, major infectious bacteria in humans (Bachir & Abouni, 2015). The obtained results are displayed in Table 6. ...
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This work aimed to study and compare the effect of the incorporation of agro-industrial by-products (chestnut shell, grapeseed, and pomegranate peel) into yoghurts to fortify them while assessing their potential to replace synthetic preservatives. From each by-product, phenolic extracts were obtained and characterized. All extracts demonstrated antioxidant and antibacterial properties, and the capacity to inhibit α-amylase. Chestnut shell extract stood out regarding antioxidant capacity, displaying values of 1128 and 972 mgTrolox∙gextract-1, for the assays with DPPH and ABTS, respectively. Ten yoghurts were produced (negative control, positive control with 0.1% of sorbic acid, two for each extract with 0.1% and 0.2% of extract, a mixture of extracts and a mixture of extracts with sorbic acid), and stored at 4 ºC. The incorporation of the extracts into the yoghurts maintained their physical-chemical properties and microbiological safety. The samples inhibited the growth of Escherichia coli and Staphylococcus aureus. Oxidative analysis proved that higher concentrations of extract had similar results to synthetic antioxidants. The results showed the viability to fortify yoghurts with the incorporation of by-product extracts, developing a value-added food. Furthermore, revealed the possibility of these extracts replacing synthetic preservatives and antioxidants.
... The antibacterial activity of the mayonnaise was assessed against S. aureus and S. epidermidis, two of the most common infectious bacteria in humans (Bachir & Abouni, 2015). The inhibition halos obtained for each bacterial strain are presented in Table 6. ...
The work studied the possibility of avocado peel extracts replacing synthetic preservatives in mayonnaise. The extracts exhibited an IC50 (concentration of extract that inhibits 50% of DPPH) value of 38.23 ± 2.33 μgextract∙mL⁻¹ and were able to inhibit more the growth of Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), compared to ascorbic acid, proving its potential to be used as a preservative. Five mayonnaises were produced (1 negative control, 2 positive controls –with 0.02% of BHT (butylated hydroxytoluene) and 0.06% of ascorbic acid, and 2 samples –with 0.5% and 1.0% of extract), and stored at 4 °C. All mayonnaises exhibited no microbial growth and inhibited the growth of Escherichia coli and Staphylococcus aureus, proving their potential to replace synthetic preservatives. Oxidative stability revealed that the samples with extract displayed analogous results to those with synthetic antioxidants, proving the possibility of the extract replacing them. The results displayed the possibility to incorporate avocado peel extracts in mayonnaises, without compromising their stability, and their potential to replace commonly used preservatives while creating value-added foods.
Industrial relevance
Avocado peels are a major by-product of avocado processing, contributing significantly to the waste generated every year. Nevertheless, it can be used to obtain extracts rich in phenolic compounds with a wide array of biological properties, that can be incorporated into different matrixes for various industries, such as food, cosmetics, and pharmaceutical. Furthermore, avocado peels are an easy-to-obtain by-product, with industrial relevance, since it allows contact between local farmers and restaurants with big industries in order to reduce the impact of this by-product while creating a value chain. Therefore, this article focuses on the incorporation of avocado peel extract into mayonnaise and its outcomes on the physical and chemical stability of the food.
This study comprehensively investigated the antioxidant properties and antibacterial activity of breadfruit (Artocarpus altilis) bark and leaf extract against two common bacterial strains, Staphylococcus aureus, and Escherichia coli. The objective was to assess the potential therapeutic applications of breadfruit extract in combating bacterial infections caused by these organisms. The researchers employed an experimental research design, utilizing controlled experiments to evaluate the effects of breadfruit extract on the target bacteria. Both the bark and leaf parts of the breadfruit plant were examined in the study. The extracts were subjected to analysis to identify and quantify the presence of beneficial compounds. The analysis revealed the presence of various compounds, including but not limited to Phenolic Acid and Flavonoids, which are known for their potential health benefits and antioxidant properties. These compounds were found to be present in relatively high concentrations, suggesting the potential of breadfruit extract as a source of natural antioxidants. In terms of antibacterial activity, the breadfruit leaf extract exhibited promising results by demonstrating significant inhibitory effects against both Staphylococcus aureus and Escherichia coli. In contrast, the bark extract showed limited effectiveness against Escherichia coli but displayed some inhibitory activity against Staphylococcus aureus. These findings suggest that breadfruit extract may have potential as a natural antimicrobial agent, particularly in combating Staphylococcus aureus infections.
In the present study, nanostructured zinc oxide (ZnO) films have been successfully synthesized using fruit extract of Viburnum opulus L. (VO) on glass slides by successive ionic layer adsorption and reaction (SILAR) procedure. The impact of VO concentrations on the structural, morphological, optical, electrical, and antibacterial attributes of ZnO films has been investigated in detail. The samples' XRD patterns present a hexagonal crystal structure with a preferential orientation along the (002) plane. The crystallite size values of ZnO samples were found to be in the ranges from 14.88 to 9.23 nm. The supplementation of VO to the synthesis solution remarkably affected the surface morphological features of the ZnO films. The optical results demonstrated that band gap energy values of the ZnO films at room temperature were decreased from 3.20 to 3.07 eV as a function of VO content in the bath solution. The films' electrical properties were determined by impedance analysis in the frequency range of 20Hz -1 MHz. Impedance-frequency measurements showed VO insertion to ZnO thin films cause an increase in impedance value at the low frequencies. Cole-Cole plots with a single semi-circle confirmed the contribution of grain and grain boundary for the electrical conduction process. The agar disk diffusion method was used to test the antibacterial properties of ZnO/VO inserted ZnO and inhibition zones were measured. VO inserted ZnO showed a stronger inhibitory effect on gram-positive bacteria Staphylococcus aureus (ATCC 25923) and gram-negative bacteria Escherichia coli (ATCC 35218) than ampicillin antibiotic used as a control group. In line with the promising bactericidal results of a new generation, VO inserted ZnO, the nanostructured product with this study, it can also be applied in multidrug-resistant clinical isolates obtained from patients.
The development of cellulose-based textiles that are functionalised with silver nanoparticles (AgNP), synthesised according to a green approach, and offer protection against ultraviolet (UV) radiation and pathogenic bacteria is very important today. In the present work we demonstrate the environmentally friendly approach to obtain such textile material by AgNP synthesis directly (in-situ) on cotton fabrics, using water extracts of plant food waste (green tea leaves, avocado seed and pomegranate peel) and alien invasive plants (Japanese knotweed rhizome, goldenrod flowers and staghorn sumac fruit) as reducing agents. The extracts were analysed for their total content of phenols and flavonoids and their antioxidant activity. The synthesised AgNP on cotton were round, of different size and amount depending on the reducing agent used. The highest amount of AgNP was found for samples where Japanese knotweed rhizome extract was used as reducing agent and the lowest where extracts of goldenrod flowers and green tea leaves were used. Regardless of the reducing agent used to form AgNP, all cotton samples showed excellent protection against E. coli and S. aureus bacteria and against UV radiation with UV protection factor values above 50. The best results for UV protection even after the twelve repetitive washing cycles were found for the sample functionalized with AgNP synthesised with an extract of the Japanese knotweed rhizome. Due to the presence of AgNP on cotton, the air permeability and thermal conductivity decreased. AgNP had no effect on the change in breaking strength or elongation of fabrics.
Graphic abstract
Phytopathogens and food-borne pathogens are a major threat to human health, so there is an urgent need to find some alternatives to overcome these issues. Nanomaterials have shown great potential as antimicrobials therefore, in this study, ZnO nanoparticles were synthesized using Azadirachta indica leaf extract and studied for their antimicrobial activity. Their antimicrobial efficacy was studied against phyto and food borne pathogens and compared with the commercially available chemically synthesized ZnO nanoparticles (Chem-ZnO-NPs). The Azadirachta indica synthesized ZnO-NPs were characterized using UV–VIS spectroscopy, DLS, and FTIR. DLS data depicts that the size of nanoparticles in colloidal solution is approximately 96 nm, with polydispersity index (PDI) of 0.37. The antimicrobial activity was studied using pour plate method. The MIC data for food borne pathogens (E. coli and S. aureus) shows that Azadirachta indica mediated ZnO-NP are more efficient as compared to Chem-ZnO-NPs. For phytopathogens (Alternaria alternata, Sclerotium rolfsii and Stemphylium solani) also the result shows that Azadirachta indica mediated ZnO-NP exhibit more efficient antifungal properties. Therefore, the synthesized ZnO-NP can be efficiently used in place of commercially available fungal pesticides.
Objectives: The study was conducted to characterize the citywide epidemiology of ESBLs in. Hail, to detect the frequency and types of enzymes.y determining whether the responsible genes.are spreading among different strains, or whether one or few strains are account for the spread.of these enzymes among the local population. Methods: One hundred urine samples were.collected and screened at local hospital during July- Aug 2011.The E.coli isolates resistant to.third generation cephalosporins (ceftazidime). The CTX-M genes were detected.y PCR and the.RAPD typing done. E-Test was performed on 30 selected isolates and were reconfirmed.y disc.diffusion method for the confirmation of resistance. Results: Polymerase chain reaction (PCR).was used to detect the ESBLs genes. The collection of ESBLs positive isolate from the hospital.and community for CTX-M were 78. Twenty two isolates did not contain.laCTX-M which may.contain.laTEM,SHV or OXA genes (not tested). The overall prevalence of isolates of E.coli was.high. ESBLs isolates were found in.oth the community and hospital, with the CTX-M type most.common.
Forty eight samples (30 wastewater and 18 river water) were collected between July and November, 2010, from different sources in Cape Town, South Africa in order to characterize verotoxic non O157: H7 Escherichia coli strains. Samples (1 ml) were inoculated into MacConkey broth (MB, 9 ml) and incubated at 37°C for 24 h, after which a loopful of the MB was then spread onto Eosin Methylene Blue (EMB) and further incubated for 24 h at 37°C in order to isolate E. coli. The identification of isolates was done using standard biochemical procedures; and confirmed serologically using E. coli polyvalent antisera (Bioweb, SA). Isolates were also characterized for virulence factors such as verotoxin, haemolysin, gelatinase, extended spectrum beta lactamases (ESBLs), cell surface hydrophobicity and bacterial serum resistance, as well as susceptibility (using disc diffusion method) to stem bark extracts of Curtisia dentata. Results showed the presence of different serotypes of E. coli (69 isolates in all) including 026: H11, 055, O111: NM, O126, O44, O124, O96:H9, O103:H2, O145: NM and O145:H2. Over 60% of the isolates exhibited serum resistance, haemolysin and gelatinase production, 81% exhibited cell surface hydrophobicity and over 52% produced ESBLs. Results also showed that while 60% of the isolates showed various levels of resistance to different antibiotics [ampicillin (10 µg), cefuroxime, cephalexin, ceftazidime and tetracycline (30 µg in each case) (multidrug resistance index (MDRI) values 4.20 to 5.60%)], only 28% were resistant to ethanol stem bark extracts of C. dentata (MIC, 70 to 150 mg/ml). The presence of pathogenic verotoxic antibiotic resistant E. coli in these water sources is a threat to water quality and food security and C. dentata has a potential for sourcing novel antibiotic substances for chemotherapy against these resistant pathogenic strains of E. coli.
Growth of Staphylococcus aureus is accompanied by production of such extracellular compounds as hemolysins, nuclease, coagulase, lipase, and enterotoxins. Enterotoxins that can cause food poisoning are produced by about one-third of the coagulase-positive strains of S. aureus. The enterotoxins are a heterogeneous group of heat-stable, water-soluble, single-chain globular proteins having a molecular weight between 28,000 and 35,000 daltons. Production of enterotoxin by appropriate strains of S. aureus is affected by the nutritional quality and pH of the substrate, temperature, atmosphere, sodium chloride (and hence water activity), other chemicals, and competing microorganisms. Outbreaks of staphylococcal food poisoning most often are associated with processed red meats, poultry products (especially chicken salad), sauces, dairy products (especially cheeses), and custard- or cream-filled bakery products. Ham and associated products often are involved in as many as 30% of outbreaks of staphylococcal food poisoning. Most outbreaks result from the combined effects of contamination of the food, often through unsanitary handling, with S. aureus and holding the food at the wrong temperature thus allowing growth and synthesis of enterotoxin by the pathogen.
The aim of this survey was to investigate the incidence of Staphylococcus aureus and coagulase-negative staphylococci and their antibiogram in food and the environment in Makkah, western Saudi Arabia. A total of 59 samples comprised of three different types of ready-to-drink raw milk (9 samples), four different types of cheese (12 samples), drinking water (10 samples), drinking water-related biofilm (18 samples) and nasal swabs of food handlers (10 samples). Staphylococci were detected using selective plating, employing Staphylococcus medium no. 110 and mannitol salt agar. Confirmation of isolates was carried out using Gram staining, production of catalase, coagulase and type of blood heamolysis. Disk diffusion method was used to test susceptibility patterns of staphylococci against seven antibiotics. The results showed that staphylococci were present in almost all types of samples. Staph. aureus were prevalent in raw milk, cheese, mucous membranes and to a degree, in biofilm. Multidrug-resistance was noted in both coagulase-positive and coagulase-negative isolates from all types of samples. A remarkable level of resistance to beta-lactams and glycopeptides was exhibited by Staph. aureus and coagulase-negative staphylococci recovered from all types of samples. The results reported in this study clearly showed the wide spread of multidrug-resistant Staph. aureus and coagulase-negative staphylococci in food and the environment and highlighted their public health hazards. To our best knowledge this study is the first to provide evidence of the existence of multidrug-resistant Staph. aureus and coagulase-negative staphylococci in food and the environment in Makkah, western Saudi Arabia.
of alternative roles of antibiotics in nature. Various groups showed their involvement in signalling pathways, weapons for carrying out competition in microbial-communities and as signalling molecules mediating chemical communication, like auto-inducers in quorum sensing inducing biofilm formation. [3] Antimicrobial resistance has not been a priority area in most developing and in many developed countries. Although resistance against antibiotics is at very high levels in many places in India, the problem remain largely unknown because there are not much studies published and relatively there is lack of a surveillance system. The issue of antibiotic resistance came into light only when New Delhi metallo-β-lactamase-1 (NDM1), first reported in 2009. [1] NDM1 is an enzyme produced by the gene bla NDM-1, carried on plasmids, could be transferred to many bacterial species, for example Klebsiella pneumoniae and Escherichia coli, conferring resistance to multiple antibiotics, including carbapenems. [1] Resistance determinants attenuating the efficacy of the antibiotics in clinical settings have shown functions that ensure self resistance. Apart from intervening resistance, all organisms requires it for detoxification of intracellular metabolites, virulence, cell homeostasis and intercellular signal trafficking. Some of these resistance determinants are transferred to the pathogen, by horizontal gene transfer, making them resistant against antibiotics that may help them to gain foothold in clinical settings. [4] Causes and prevention Figure 1 shows the ability of bacteria to transfer genes from one bacterium to another by lateral gene transfer (LGT), which has played an integral role in evolution and diversification of antibiotic resistance in bacteria. [5,6] Primarily, drug resistance has been recognised a medical problem. However, the factors which really influence the
This study investigated the isolation rate and antimicrobial susceptibility of Escherichia coli and other coliforms from asymptomatic male and female students of Niger Delta University in Bayelsa State, Nigeria. E. coli and other coliforms from midstream clean-catch urine samples of asymptomatic male and female students were isolated and tested for their susceptibility to commonly used antimicrobial agents using the disk diffusion protocol described by the Clinical Laboratory Standards Institute (CLSI). Of the few subjects that harbored E. coli, more were males. Zone sizes for both isolate groups from males were higher than those from females. E. coli were more susceptible to the antimicrobials than the non -E. coli (unclassified coliform) isolates for both subjects, although the overall susceptibility of both isolate groups was poor. Gentamicin was the most active (64.5% for E. coli and 33.3% for unclassified coliforms) while tetracycline was the least (22.7% for E. coli and 0% for unclassified coliforms). The most common resistance phenotypes were "ATCtGSNa" (for E. coli) and "ATCtGSNaNC" (for unclassified coliforms); "ATCtGSNaNC" was observed in both isolate groups. Multiple antibiotic resistances were observed significantly in both E. coli (83.9%) and the unclassified coliforms (100%). As against 9.7% of the E. coli isolates, 40% of the unclassified coliforms were resistant to all the antimicrobials. MAR indices were very high (all above 0.2) in both isolate groups. Although asymptomatic male students of Niger Delta University harbored more E. coli than the female students, isolates from the female students pose greater risk of antimicrobial resistance owing to their lower susceptibility to antimicrobials compared with those from their male counterparts. The prior exposure of all the isolates to antibiotics as suggested by their high MAR indices provides justification for continuous monitoring of bacterial susceptibility to antibiotics before prescription in order to ensure adequate treatment of infections arising from urinary pathogens and reduction in the spread of bacteria resistant strain.
Antimicrobial resistance (AMR) in bacteria is the end result of a multitude of factors. Some of the key factors beyond innate resistance include antimicrobial selective pressure (1–5), acquisition of a foreign genetic resistance element(s) (1–5), clonal dissemination (1) and new mutations (2,3,5); factors vary for different species and geographical locations. Increased global antimicrobial use is the foremost reason for the spread of AMR in the community setting (1). Social networks of individuals (households, schools and child care facilities) have served both as a reservoir for these bacteria and as a common route for their transmission. Similarly, hospitals, nursing homes and long-term care facilities have also served as reservoirs for antibiotic-resistant organisms, and the discharge of patients from these facilities contributes to the spread of resistance within communities. In addition, the use of antimicrobials in food animals has been an important contributing cause (1).
Eleven multidrug-resistant Escherichia coli isolates (comprising 6 porcine and 5 bovine field isolates) displaying fluoroquinolone (FQ) resistance were selected from a collection obtained from the University Veterinary Hospital (Dublin, Ireland). MICs of nalidixic acid and ciprofloxacin were determined by Etest. All showed MICs of nalidixic acid of >256 μg/ml and MICs of ciprofloxacin ranging from 4 to >32 μg/ml. DNA sequencing was used to identify mutations within the quinolone resistance-determining regions of target genes, and quantitative real-time PCR (qRT-PCR) was used to evaluate the expression of the major porin, OmpF, and component genes of the AcrAB-TolC efflux pump and its associated regulatory loci. Decreased MIC values to nalidixic acid and/or ciprofloxacin were observed in the presence of the efflux pump inhibitor phenylalanine-arginine-β-naphthylamide (PAβN) in some but not all isolates. Several mutations were identified in genes coding for quinolone target enzymes (3 to 5 mutations per strain). All isolates harbored GyrA amino acid substitutions at positions 83 and 87. Novel GyrA (Asp87 → Ala), ParC (Ser80 → Trp), and ParE (Glu460 → Val) substitutions were observed. The efflux activity of these isolates was evaluated using a semiautomated ethidium bromide (EB) uptake assay. Compared to wild-type E. coli K-12 AG100, isolates accumulated less EB, and in the presence of PAβN the accumulation of EB increased. Upregulation of the acrB gene, encoding the pump component of the AcrAB-TolC efflux pump, was observed in 5 of 11 isolates, while 10 isolates showed decreased expression of OmpF. This study identified multiple mechanisms that likely contribute to resistance to quinolone-based drugs in the field isolates studied.
Staphylococcal species, notably, coagulase-negative staphylococci (CoNS), are frequently misidentified using phenotypic methods. The partial nucleotide sequences of the tuf and gap genes were determined in 47 reference strains to assess their suitability, practicability, and discriminatory power as target molecules for staphylococcal identification. The partial tuf gene sequence was selected and further assessed with a collection of 186 strains, including 35 species and subspecies. Then, to evaluate the efficacy of this genotyping method versus the technology of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), the 186 strains were identified using MALDI-TOF-MS (Axima® Shimadzu) coupled to the SARAMIS® database (AnagnosTec). The French National Reference Center for Staphylococci identification method was used as a reference. One hundred and eighty-four strains (98.9%) were correctly identified by tuf gene sequencing. Only one strain was misidentified and one was unidentified. MALDI-TOF-MS identified correctly 138 isolates (74.2%). Four strains were misidentified, 39 were unidentified, five were identified at the group (hominis/warneri) level, and one strain was identified at the genus level. These results confirm the value of MALDI-TOF-MS identification for common species in clinical laboratory practice and the value of the partial tuf gene sequence for the identification of all staphylococcal species as required in a reference laboratory.
Over the last decade, methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged as serious pathogens in the nosocomial and community setting. Hospitalization costs associated with MRSA infections are substantially greater than those associated with methicillin-sensitive S. aureus (MSSA) infections, and MRSA has wider economic effects that involve indirect costs to the patient and to society. In addition, there is some evidence suggesting that MRSA infections increase morbidity and the risk of mortality. Glycopeptides are the backbone antibiotics for the treatment of MRSA infections. However, several recent reports have highlighted the limitations of vancomycin, and its role in the management of serious infections is now being reconsidered. Several new antimicrobials demonstrate in vitro activity against MRSA and other Gram-positive bacteria. Data from large surveys indicate that linezolid, daptomycin, and tigecycline are almost universally active against MRSA. This review will briefly discuss the epidemiology, costs, outcome, and therapeutic options for the management of MRSA infections.
Staphylococcus aureus is a well adapted human pathogen, capable of living freely in the inanimate environment and spreading from person to person, existing as a colonizer or commensal, hiding in intracellular compartments and, most importantly, inducing various forms of human disease. Infections caused by S. aureus, above all by antibiotic-resistant strains, have reached epidemic proportions globally. The overall burden of staphylococcal disease caused by antibiotic-resistant S. aureus, particularly by the methicillin-resistant strains, is increasing in many countries, including Italy, in both healthcare and community settings. The widespread use of antibiotics has undoubtedly accelerated the evolution of S. aureus, which, acquiring multiple resistance genes, has become able to survive almost all antibiotic families; this evolution versus more resistant phenotypes has continued among the newer agents, including linezolid and daptomycin. The diminished clinical usefulness of vancomycin is seen as one of the most worrisome problems in many clinical settings and in many countries. In fact, the increasing spread of heteroresistant vancomycin-intermediate S. aureus (hVISA) and vancomycin intermediate (VISA) strains adds new problems, not only in terms of the treatment of severe infections sustained by these microorganisms, but also in the microbiological definition of susceptibility.
Since the introduction of penicillin, beta-lactam antibiotics have been the antimicrobial agents of choice. Unfortunately, the efficacy of these life-saving antibiotics is significantly threatened by bacterial beta-lactamases. beta-Lactamases are now responsible for resistance to penicillins, extended-spectrum cephalosporins, monobactams, and carbapenems. In order to overcome beta-lactamase-mediated resistance, beta-lactamase inhibitors (clavulanate, sulbactam, and tazobactam) were introduced into clinical practice. These inhibitors greatly enhance the efficacy of their partner beta-lactams (amoxicillin, ampicillin, piperacillin, and ticarcillin) in the treatment of serious Enterobacteriaceae and penicillin-resistant staphylococcal infections. However, selective pressure from excess antibiotic use accelerated the emergence of resistance to beta-lactam-beta-lactamase inhibitor combinations. Furthermore, the prevalence of clinically relevant beta-lactamases from other classes that are resistant to inhibition is rapidly increasing. There is an urgent need for effective inhibitors that can restore the activity of beta-lactams. Here, we review the catalytic mechanisms of each beta-lactamase class. We then discuss approaches for circumventing beta-lactamase-mediated resistance, including properties and characteristics of mechanism-based inactivators. We next highlight the mechanisms of action and salient clinical and microbiological features of beta-lactamase inhibitors. We also emphasize their therapeutic applications. We close by focusing on novel compounds and the chemical features of these agents that may contribute to a "second generation" of inhibitors. The goal for the next 3 decades will be to design inhibitors that will be effective for more than a single class of beta-lactamases.
The prospective, multicenter, double-blind study presented in this report evaluated whether or not intravenous (IV) administration of doripenem, a carbapenem with bactericidal activity against gram-negative and gram-positive uropathogens, is inferior to IV administration of levofloxacin in the treatment of complicated urinary tract infection (cUTI). Patients (n = 753) with complicated lower UTI or pyelonephritis were randomly assigned to receive IV doripenem at 500 mg every 8 h (q8h) or IV levofloxacin at 250 mg q24h. Patients in both treatment arms were eligible to switch to oral levofloxacin after 3 days of IV therapy to complete a 10-day treatment course if they demonstrated significant clinical and microbiological improvements. The microbiological cure rate (primary end point) was determined at the test-of-cure (TOC) visit occurring 5 to 11 days after the last dose of antibiotic. For the microbiologically evaluable patients (n = 545), the microbiological cure rates were 82.1% and 83.4% for doripenem and levofloxacin, respectively (95% confidence interval [CI] for the difference, -8.0 to 5.5%); in the microbiological modified intent-to-treat cohort (n = 648), the cure rates were 79.2% and 78.2%, respectively. Clinical cure rates at the TOC visit were 95.1% in the doripenem arm and 90.2% in the levofloxacin arm (95% CI around the difference in cure rates [doripenem cure rate minus levofloxacin cure rate], 0.2% to 9.6%). Both treatment regimens were generally well tolerated. Doripenem was found not to be inferior to levofloxacin in terms of therapeutics and is now approved for use in the United States and Europe for the treatment of adults with cUTI, including pyelonephritis. As fluoroquinolone resistance increases, doripenem may become a more important option for successful treatment of cUTIs, including treatment of pyelonephritis.
To describe the predictive factors for the isolation of fluoroquinolone-resistant or extended- spectrum beta-lactamase (ESBL)-producing Escherichia coli and their impact on bacteraemia outcome.
Analysis of E. coli bacteraemia episodes prospectively collected through a blood culture surveillance programme from January 1991 to December 2007.
Out of 18 080 episodes, 4758 (26%) E. coli bacteraemias were reported in the period of study. Mortality was noted in 440 cases (9%). Fluoroquinolone-resistant strains were reported in 1300 (27%) cases and ESBL-producing strains in 211 cases (4%). One hundred and seventy-eight strains out of 211 (84%) ESBL-producing E. coli were isolated since 2001. The two main independent risk factors for mortality were shock (OR: 10.28, P < 0.001) and inappropriate empirical therapy (OR: 4.83, P < 0.001). Inappropriate empirical therapy was significantly more frequent for infections caused by fluoroquinolone-resistant strains (n = 203, 16%, P < 0.001) and ESBL-producing strains (n = 110, 52%, P < 0.001). Independent factors associated with the isolation of a fluoroquinolone-resistant strain were: nosocomial origin (OR: 1.61, P < 0.001); urinary catheterization (OR: 2.44, P < 0.001); and previous therapy with a fluoroquinolone (OR: 7.41, P < 0.001). The independent risk factors associated with the isolation of an ESBL-producing strain were: nosocomial origin (OR: 1.68, P = 0.03); urinary catheterization (OR: 1.88, P = 0.001); and previous beta-lactam antibiotic therapy (OR: 2.81, P < 0.001).
Inappropriate empirical therapy was the strongest independent factor that we could modify to improve mortality in E. coli bacteraemia and was more frequent in cases caused by fluoroquinolone-resistant or ESBL-producing strains. Nosocomial acquisition, urinary catheterization and previous therapy with a fluoroquinolone or beta-lactam were predictive factors for infection with an antibiotic-resistant strain.
Staphylococcus aureus is an important pathogen that forms biofilms. The global regulator sarA is essential for biofilm formation. Since the modulator of sarA (msa) is required for full expression of sarA and regulates several virulence factors, we examined the capacity of the msa mutant to form biofilm.
We found that mutation of msa results in reduced expression of sarA in biofilm and that the msa mutant formed a weak and unstable biofilm. The msa mutant is able to adhere to surfaces and begins to form biofilm but fails to mature indicating that the defect of the msa mutant biofilm is in the accumulation stage but not in primary adhesion.
The msa gene plays an important role in biofilm development which is likely due to its role in modulating the expression of sarA. This finding is significant because it identifies a new gene that plays a role in the development of biofilm.
A PCR-restriction fragment length polymorphism (RFLP) analysis method that analyzes a part of the dnaJ gene was designed for the rapid and accurate identification of Staphylococcus spp. XapI or Bsp143I digestion of the PCR-generated products rendered distinctive RFLP patterns that allowed 41 reference
species and subspecies to be identified with a high degree of specificity. The novel method was validated by the identification
of 23 clinical staphylococcal strains, and the results were compared with those obtained by other genotypic identification
methods. A 100% concordance of the results was shown. Therefore, PCR-RFLP analysis of the dnaJ gene is proposed as a reliable and reproducible method for the identification of Staphylococcus spp.
Staphylococci remain the most important cause of hospital-acquired infections in the U.S. and MRSA has become the most common cause of skin and soft tissue infection in many parts of the world. There is now a much greater understanding of the physiology and evolution of the staphylococci and this new edition reflects the rapid advancements in knowledge about this pathogen and provides a comprehensive review from both clinical and basic science perspectives. The first section addresses the basic biology of the staphylococci, their molecular genetics, host defenses and host evasion, virulence determinants, mechanisms of antibiotic resistance, and laboratory techniques. The second section deals with epidemiology, and the third section provides an overview of the varied clinical manifestations of human staphylococcal infections. The fourth section covers prevention and treatment of these often life-threatening infections. Written by experts from around the globe, this book is essential reading for all clinicians and basic scientists studying the staphylococci.
Serious infections caused by resistant gram-positive cocci continue to increase in prevalence and significance. An NDA for ceftobiprole, an investigational novel broad-spectrum cephalosporin antibiotic, was submitted on May 18, 2007, for the treatment of complicated skin and skin-structure infections (cSSSis), including diabetic foot infections. Ceftobiprole has demonstrated in vitro and in vivo activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate S aureus (VISA), vancomycin-resistant S aureus (VRSA), multidrug-resistant Streptococcus pneumoniae, Enterococcus faecalis, and some gram-negative bacteria, including Enterobacteriaceae that do not produce extended-spectrum beta-lactamases (ESBLs) and ceftazidime/cefepime-susceptible Pseudomonas aeruginosa. In clinical trials, ceftobiprole has demonstrated noninferiority to vancomycin monotherapy and vancomycin plus ceftazidime for the treatment of cSSSis. Phase 3 clinical trials have also been conducted to assess ceftobiprole's efficacy in the treatment of community- and hospital-acquired pneumonia; full results have not yet been released. Ceftobiprole was well tolerated in clinical trials, with patients experiencing only mild adverse events (most commonly a caramel taste alteration after administration). If approved, ceftobiprole's in vitro activity against resistant gram-positive bacteria, particularly MRSA, combined with its demonstrated clinical efficacy for the treatment of cSSSis and its mild adverse-event profile, will likely make the drug an attractive addition to the antimicrobial armamentarium.
Staphylococcus aureus has the ability to cause a wide variety of human diseases: from superficial abscesses and wound infections to deep and systemic infections such as osteomyelitis, endocarditis and septicaemia. S. aureus invasion might be involved in some of the unique pathogenic manifestations of this bacterium, including long-term colonization. The ability to cause disease is a result of presence of virulence factors. Virulence factors are synthesized in response to the specific needs during the infectious process. The molecular mechanism and the precise role of invasion in S. aureus pathology are not known. S. aureus expresses many potential virulence factors: surface proteins, invasins (leukocidin, kinases hyaluronidase), inhibitors of phagocytic engulfment (capsule, Protein A), factors enhancing bacterial survival in phagocytes (carotenoids, catalase production), immunological disguises (Protein A, coagulase, clotting factor), membrane- damaging toxins (hemolysins, leukotoxin, leukocidin) and exotoxins (SEA-G, TSST, ET). The pathogenicity of S. aureus infections is related to surface components including those recognizing adhesive matrix molecules (e.g., clumping factor and fibronectin binding protein) and to extracellular proteins [e.g., coagulase, hemolysins, enterotoxins, toxic-shock syndrome (TSS) toxin, exfoliatins, and Panton-Valentine leukocidin (PVL)]. In general, the precise roles of individual staphylococcal factors in invasive infections are difficult to assess.
E Coli isolates from urine samples of patients suffering from Urinary Tract Infections caused by E Coli was collected from various private diagnostic centers in Davangere, Karnataka, India. Isolates were cultured and maintained using specific media. Urea and Salinity tolerance of samples was checked by observing bacterial growth in artificial urine with varying urea and salt concentrations. Biochemical assays were carried out to identify virulence factors of Uropathogenic E Coli in samples showing high salt and urea tolerance.
Previously our laboratory had identified a novel component of the Staphylococcus aureus regulatory network, an extracytoplasmic function ó factor, óS, involved in stress response and disease causation. Here we present additional characterization of óS, demonstrating a role for it in protection against DNA damage, cell wall disruption and interaction with components of the innate immune system. Promoter mapping reveals the existence of four unique sigS start sites, one of which appears to be subject to auto-regulation. Transcriptional profiling revealed that sigS expression remains low in a number of S. aureus wild-types, but is upregulated in the highly mutated strain RN4220. Further analysis demonstrates sigS expression is inducible upon exposure to a variety of chemical stressors that elicit DNA damage, including methyl methanesulfonate (MMS) and ciprofloxacin, as well as those that disrupt cell wall stability, such as ampicillin and oxacillin. Ex vivo transcriptional analysis reveals that significant expression of sigS can be induced upon phagocytosis by RAW 264.7 murine macrophage-like cells. Regulation of óS appears to be unique, as the downstream encoded protein, SACOL1828, seemingly acts as a positive activator, rather than as an expected anti-sigma factor. Using a global transposon screen we have elucidated additional genes implicated in the regulation of sigS, including those involved in cell wall stability, cellular detoxification, virulence and DNA base excision repair. Phenotypically, óS mutants display sensitivity to a broad range of DNA damaging agents, such as ultraviolet light, MMS and ethidium bromide. These effects are seemingly mediated via regulation of the purine biosynthesis pathway, as microarray, proteomic and qRT-PCR analysis of óS mutants reveal decreased transcription of all genes involved. Enzymatic profiling of PurA involved in adenine biosynthesis, demonstrates decreased activity in the óS mutant. Finally, we provide further evidence for the role of óS in S. aureus pathogenesis, revealing that sigS mutants display decreased ability to cause localized infections and are impaired in their interactions with components of the human innate immune system. Collectively, our data argues for the important, and perhaps novel, role of óS in the stress and virulence responses of S. aureus.
Food-borne diseases are of major concern worldwide. To date, 250 different food- borne diseases have been described and bacteria are the causative agents of two thirds of food-borne disease outbreaks. Food poisoning is a term used to express any type of disease, illness or malaffect after consuming food. The most serious type of food poisoning is bacterial food poisoning, which may be due to bacterial infection or food intoxication. Among the predominant bacteria involved in these diseases, Staphylococcus aureus is a leading cause of gastroenteritis resulting from the consumption of a food in which enterotoxigenic staphylococci have grown and produced toxins. As these toxins are excreted from the organism, they are referred to as exotoxins; however, they normally exert their effects on the gastrointestinal tract and therefore are called enterotoxins. While not considered a highly lethal agent due to the low mortality associated with the illness, staphylococcal enterotoxins are considered a potential biological threat because of their stability at high temperatures (100°C for 1 h) and ability to incapacitate individuals for several days to two weeks. Here, a brief review on Staphylococcal enterotoxins is given.
This report represents an important initiative on the part of the Intelligence Community to consider the national security dimension of a nontraditional threat. It responds to a growing concern by senior US leaders about the implications--in terms of health, economics, and national security--of the growing global infectious disease threat. The dramatic increase in drug resistant microbes, combined with the lag in development of new antibiotics, the rise of megacities with severe health care deficiencies, environmental degradation, and the growing ease and frequency of cross-border movements of people and produce have greatly facilitated the spread of infectious diseases. In June 1996, President Clinton issued a Presidential Decision Directive calling for a more focused US policy on infectious diseases. The State Department's Strategic Plan for International Affairs lists protecting human health and reducing the spread of infectious diseases as US strategic goals, and Secretary Albright in December 1999 announced the second of two major U.S. initiatives to combat HIV/AIDS. The unprecedented UN Security Council session devoted exclusively to the threat to Africa from HIV/ AIDS in January 2000 is a measure of the international community's concern about the infectious disease threat. As part of this new US Government effort, the National Intelligence Council produced this National Intelligence Estimate.
Escherichia coli remains one of the most frequent causes of nosocomial and community-acquired bacterial infections including urinary tract infections, enteric infections and systemic infections in humans. Extraintestinal pathogenic E. coli (ExPEC) had emerged during the 2000s as an important player in the resistance to antibiotics, especially to the cephalosporins and fluoroquinolones. Most importantly, among ExPEC is the increasing recognition of isolates producing 'newer β-lactamases' that consist of plasmid-mediated AmpC β-lactamases (e.g., CMY), extended-spectrum β-lactamases (e.g., CTX-M) and carbapenemases (e.g., New Delhi metallo-β-lactamase, Klebsiella pneumonaie carbapenemase and OXA-48). This review will highlight recent aspects on antimicrobial resistance in ExPEC, including the laboratory detection of these isolates, and describe some treatment options for infections due to antimicrobial-resistant isolates.
Staphylococcus aureus bacteremia (SAB) is an important infection with an incidence rate ranging from 20 to 50 cases/100,000 population per year. Between 10% and 30% of these patients will die from SAB. Comparatively, this accounts for a greater number of deaths than for AIDS, tuberculosis, and viral hepatitis combined. Multiple factors influence outcomes for SAB patients. The most consistent predictor of mortality is age, with older patients being twice as likely to die. Except for the presence of comorbidities, the impacts of other host factors, including gender, ethnicity, socioeconomic status, and immune status, are unclear. Pathogen-host interactions, especially the presence of shock and the source of SAB, are strong predictors of outcomes. Although antibiotic resistance may be associated with increased mortality, questions remain as to whether this reflects pathogen-specific factors or poorer responses to antibiotic therapy, namely, vancomycin. Optimal management relies on starting appropriate antibiotics in a timely fashion, resulting in improved outcomes for certain patient subgroups. The roles of surgery and infectious disease consultations require further study. Although the rate of mortality from SAB is declining, it remains high. Future international collaborative studies are required to tease out the relative contributions of various factors to mortality, which would enable the optimization of SAB management and patient outcomes.
The occurrence of multiple strains of Staphylococcus aureus colonizing the nasal mucosa of food handlers was investigated. Samples were collected from the anterior nares of 47 food handlers and were streaked on plates of Baird-Parker agar. From each plate, three typical colonies of S. aureus, with similar morphologies, were picked up and identified by biochemical tests. S. aureus isolates were typed by antibiotic susceptibility and pulsed-field gel electrophoresis (PFGE). Results indicated nasal carriage of S. aureus in 14 (30%) of the personnel. The isolated micro-organisms were resistant to penicillin and amoxicillin+clavulanic acid (70% and 45% of the isolates, respectively). All isolates were sensitive to vancomycin, rifampicin, cephalothin, oxacillin, chloramphenicol, gentamycin, and ofloxacin. Typing methods indicated that 11 among the 14 food handlers harbored multiple strains of S. aureus per carrier. Such results demonstrate that multiple isolates of S. aureus need to be strain-typed per food handler when attempts are made to identify sources of food poisoning, in epidemiological studies and in investigations of food contamination sources.
Neonatal Escherichia coli meningitis continues to be an important cause of mortality and morbidity throughout the world. The major contributing factors to this mortality and morbidity include our incomplete knowledge on its pathogenesis and an emergence of antimicrobial-resistant E. coli. Recent reports of neonatal meningitis caused by E. coli producing CTX-M-type or TEM-type extended-spectrum β-lactamases create a challenge, and innovative approaches are needed to identify potential targets for prevention and therapy of E. coli meningitis.
E. coli invasion of the blood-brain barrier is a prerequisite for penetration into the brain and requires specific microbial-host factors as well as microbe-specific and host-specific signaling molecules. Recent studies identified additional microbial and host factors contributing to E. coli invasion of the blood-brain barrier and elucidated their underlying mechanisms. Blockade of the microbial-host factors contributing to E. coli invasion of the blood-brain barrier was shown to be efficient in preventing E. coli penetration into the brain.
Continued investigation on the microbial-host factors contributing to E. coli invasion of the blood-brain barrier is needed to identify new targets for prevention and therapy of E. coli meningitis, thereby limiting the exposure to emerging antimicrobial-resistant E. coli.
Urinary tract infections (UTIs) are among the most common bacterial infections acquired in the community and in hospitals. In individuals without anatomical or functional abnormalities, UTIs are generally self limiting, but have a propensity to recur. Uropathogens have specialized characteristics, such as the production of adhesins, siderophores and toxins that enable them to colonize and invade the urinary tract, and are transmitted between individuals both through person-to-person contact and possibly via food or water. Although generally self limiting, treatment of UTIs with antibiotics leads to a more rapid resolution of symptoms and is more likely to clear bacteriuria, but also selects for resistant uropathogens and commensal bacteria and adversely affects the gut and vaginal microbiota. As uropathogens are increasingly becoming resistant to currently available antibiotics, it may be time to explore alternative strategies for managing UTI.
Clin Microbiol Infect 2011; 17: 557–565
Escherichia coli is one of the major pathogens responsible for bactaeremia. Empirical antibiotherapy of these infections usually relies on third-generation cephalosporins (3GCs). Thus, the occurrence and epidemiology of 3GC-resistant strains have to be monitored. The French prospective multicentre study COLIBAFI collected 1081 strains of E. coli responsible for bacteraemia in 2005. In the present work, the prevalence of resistance to 3GCs was evaluated, and the implicated molecular mechanisms were characterized by specific PCR and sequencing. Phylogenetic grouping, O-typing, pulsed-field gel electrophoresis and virulence factor analysis were used to investigate the genetic background of the 3GC-resistant (3GC-R) strains. Clinical features of the patients with documented data (n = 1051) were analysed. Decreased susceptibility to 3GCs was observed in 41 strains (3.8%): 19, 18 and four had extended-spectrum β-lactamase (ESBL), AmpC cephalosporinase and OXA-type penicillinase phenotypes, respectively. Pulsed-field gel electrophoresis revealed that the 3GC-R strains constitute a diverse population. All but one of the strains with an ESBL phenotype produced a CTX-M-type enzyme, and six of them belonged to the widespread intercontinental clone O25b:H4-ST131. AmpC phenotype strains harboured various chromosomal ampC promoter and coding region mutations and/or the blaCMY-2 plasmidic gene. 3GC-R strains carried fewer virulence factors and were more co-resistant to other antibiotics than 3GC-susceptible (3GC-S) strains. Infections with 3GC-R strains were mostly community-acquired and, as compared with those caused by their 3GC-S counterparts, were more severe. Underlying chronic disease and prior use of antibiotics were independent risk factors for development of a 3GC-R strain bacteraemia. The fact that the molecular support of 3GC resistance is mainly plasmid-mediated represents a potentially epidemic threat.
Water from dental equipment presents risks for surgeon-dentists as well as for patients because it might work as a means of dissemination/transmission of microorganisms. The objective of this study was to verify the quality of the water used in dental equipment by means of microbiological analysis, accomplishing the count of Staphylococcus spp. There have been collected 160 samples of water from reservoirs, taps used for hand washing, air-water syringes, and high-speed handpieces, in 40 dental offices in the city of Barretos, São Paulo. The rules concerning bacteriological analysis in cfu/mL from Standard Methods for the Examination of Water and Wastewater have been followed. The analysis of the results has made it possible to verify that out of the total of samples, 28% did not meet the standards of potability established by the American Dental Association. Regarding the origin of analyzed S. aureus, the most contaminated sites were high-speed handpieces in private offices (76%) and in dental care plan offices (71%), followed by air-water syringe in dental care plan offices (64%). For S. epidermidis samples, the most contaminated sites were high-speed handpieces in SUS (Brazilian Government Health System) dental offices (22%) and in dental care plan offices (14%). The most contaminated sites were dental offices that saw patients under dental care plans. Concerning tested antibiotics, the ones that presented better results as to sensibility to strain S. epidermidis were vancomycin and ciprofloxacin (100%) and, as to sensibility to strain S. aureus, it was ciprofloxacin (97%).
Staphylococcus aureus is a major cause of bacteremia, and S. aureus bacteremia is associated with higher morbidity and mortality, compared with bacteremia caused by other pathogens. The burden
of S. aureus bacteremia, particularly methicillin-resistant S. aureus bacteremia, in terms of cost and resource use is high. The risk of infective endocarditis and of seeding to other metastatic
foci increases the risk of mortality and raises the stakes for early, appropriate treatment. The incidence of S. aureus bacteremia and its complications has increased sharply in recent years because of the increased frequency of invasive procedures,
increased numbers of immunocompromised patients, and increased resistance of S. aureus strains to available antibiotics. This changing epidemiology of S. aureus bacteremia, in combination with the inherent virulence of the pathogen, is driving an urgent need for improved strategies
and better antibiotics to prevent and treat S. aureus bacteremia and its complications.
The frequency of infections caused by multidrug-resistant Staphylococcus aureus continues to increase while the numbers of alternative therapeutic agents remain limited. To investigate the changing patterns
of in-vitro susceptibility of S. aureus to 16 antibiotics, 190 clinical isolates from two different years were studied. The MICs of methicillin-susceptible (MSSA)
and methicillin-resistant (MRSA) strains isolated in 1987 were compared with those of similar numbers of strains isolated
in 1989. For MRSA ≥90% of isolates from both years were resistant to clindamycin, gentamicin and erythromycin. These strains
remained highly susceptible to vancomycin (100%), minocycline (90%) and rifampicin (100%). The greatest increase in resistance
was observed for ofloxacin (2% in 1987 vs 62% in 1989); cross-resistance to all of the quinolones tested was demonstrated.
MSSA strains remained susceptible to vancomycin (100%), minocycline (98%), rifampicin (100%), clindamycin (90%), gentamicin
(90%) and ciprofloxacin (98%). It is concluded that methicillin susceptibility is a useful marker for selecting potential
agents for the treatment of infections caused by S. aureus. A combination of minocydine and rifampicin may be a useful alternative to vancomycin for treating MRSA infections.
The use of fluoroquinolones as oral therapeutic agents for staphylococcal infections, problems with bacterial resistance, and approaches to suppression of resistance are discussed. Although they are particularly effective for treatment of gram-negative bacillary infections, quinolones, including ciprofloxacin and pefloxacin in limited experience, have been effective in treating staphylococcal infections. Clinical failures have occurred, however, in association with emergence of resistance or poor delivery of drug to the infected site. Recent surveys of drug susceptibility reveal substantial increases in resistance among methicillin-resistant and to a lesser extent methicillin-susceptible Staphylococcus aureus. Some strains were isolated from patients not receiving quinolone therapy. Resistance occurs by mutation in chromosomal genes, by mechanisms not yet defined, but probably involving either alteration of the target enzyme DNA gyrase or changes in drug accumulation, or both. Strategies to suppress emergence of fluoroquinolone resistance should be evaluated, including prudent drug use, use of combination drug therapy, and development of fluoroquinolone derivatives that have a higher therapeutic index and are less prone to select resistant organisms.
For 77 strains of Staphylococcus aureus freshly isolated from different foods, growth, enterotoxin and TNase production were determined in intervals of 1.5 degrees C +/- 0.5 degrees C by cultivating them in a temperature-gradient incubator between 5 and 50 degrees C for up to 7 days. All the strains were coagulase, DNase and lysostaphin positive but only 58% formed one or two enterotoxins type SEA, SEB or SEE. All strains grew within 7 days in brain heart infusion and had lower and upper temperature limits for growth and TNase production of between 6.5 and 12.5 degrees C, and 39.5 and 48.5 degrees C respectively. The lower and upper temperature limits for production of enterotoxins were between 14 and 38 degrees C, and between 35 and 44 degrees C respectively. Enterotoxin forming isolates either showed narrow (3 to 4 degrees C) or wide (10 to 20 degrees C) ranges of enterotoxin production, irrespective of their temperature range of growth and TNase production. None of the 12 specific physiological attributes used for differentiation could be correlated to toxin type or the temperature requirement of the toxin production. No correlation between the origin and the physiological characters could be detected.
Since January 1988, Staphylococcus aureus strains with a high level of quinolone resistance have been isolated at 17 hospitals and 15 nursing homes in New York City. The majority of these strains were methicillin resistant. The bacteriophage types and susceptibility to other antibiotics were similar to those of quinolone-susceptible strains isolated at the same hospitals.
Ofloxacin and ciprofloxacin resistance (MIC, greater than 4 micrograms/ml) was encountered in 45 of 50 clinical isolates of
methicillin-resistant Staphylococcus aureus. None of 20 methicillin-susceptible strains was resistant to the quinolones (P
less than 10(-6). Quinolone-susceptible and -resistant isolates did not differ with respect to culture source or bacteriophage
type. The future usefulness of quinolones for S. aureus infection may be limited.
There are four major categories of diarrheagenic Escherichia coli: enterotoxigenic (a major cause of travelers' diarrhea and infant diarrhea in less-developed countries), enteroinvasive (a
cause of dysentery), enteropathogenic (an important cause of infant diarrhea), and enterohemorrhagic (a cause of hemorrhagic
colitis and hemolytic uremic syndrome). Besides manifesting distinct clinical patterns, these categories of E. coli differ in their epidemiology and pathogenesis and in their O:H serotypes. Common features (albeit distinct for each category)
include plasmid-encoded virulence properties, characteristic interactions with intestinal mucosa, and elaboration of various
types of enterotoxins or cytotoxins. A less-well-defined fifth category of diarrheagenic E. coli is that of enteroadherent E. coli, so far identifiable only by their pattern of adherence to Hep-2 cells in tissue culture.