[Show abstract][Hide abstract] ABSTRACT: Candida albicans, an opportunistic pathogen, has been known to form hypoxic biofilms on medical devices which in turn confers resistance towards antifungals, resulting in subsequent therapeutic failures. Inclusion of anti-biofilm agents in the control of infections is a topic of current interest in developing potential anti-infectives. The in vitro anti-fungal and anti-biofilm efficacy of 2,4-di-tert-butyl phenol [DTBP] was evaluated in this study, which revealed the potential fungicidal action of DTBP at higher concentrations where fluconazole failed to act completely. DTBP also inhibited the production of hemolysins, phospholipases and secreted aspartyl proteinase which are the crucial virulence factors required for the invasion of C. albicans. Various anti-biofilm assays and morphological observations revealed the efficacy of DTBP in both inhibiting and disrupting biofilms of C. albicans. Inhibition of hyphal development, a key process that aids in initial adhesion of C. albicans, was observed, and this could be a mechanism for the anti-biofilm activity of DTBP.
[Show abstract][Hide abstract] ABSTRACT: The present study explores the efficacy of limonene, a cyclic terpene found in the rind of citrus fruits, for antibiofilm potential against species of the genus Streptococcus, which have been deeply studied worldwide owing to their multiple pathogenic efficacy. Limonene showed a concentration-dependent reduction in the biofilm formation of Streptococcus pyogenes (SF370), with minimal biofilm inhibitory concentration (MBIC) of 400 μg ml - 1. Limonene was found to possess about 75-95 % antibiofilm activity against all the pathogens tested, viz. Streptococcus pyogenes (SF370 and 5 clinical isolates), Streptococcus mutans (UA159) and Streptococcus mitis (ATCC 6249) at 400 μg ml - 1 concentration. Microscopic analysis of biofilm architecture revealed a quantitative breach in biofilm formation. Results of a surface-coating assay suggested that the possible mode of action of limonene could be by inhibiting bacterial adhesion to surfaces, thereby preventing the biofilm formation cascade. Susceptibility of limonene-treated Streptococcus pyogenes to healthy human blood goes in unison with gene expression studies in which the mga gene was found to be downregulated. Anti-cariogenic efficacy of limonene against Streptococcus mutans was confirmed, with inhibition of acid production and downregulation of the vicR gene. Downregulation of the covR, mga and vicR genes, which play a critical role in regulating surface-associated proteins in Streptococcus pyogenes and Streptococcus mutans, respectively, is yet further evidence to show that limonene targets surface-associated proteins. The results of physiological assays and gene expression studies clearly show that the surface-associated antagonistic mechanism of limonene also reduces surface-mediated virulence factors.
Journal of Medical Microbiology 08/2015; 64(8):879-90. DOI:10.1099/jmm.0.000105 · 2.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Epibacterial communities of co-occurring eukaryotic hosts of Palk Bay origin (five seaweed species (Gracilaria sp, Padina sp, Enteromorpha sp, Sargassum sp, and Turbinaria sp) and one seagrass [Cymodaceae sp]) were analyzed for diversity and compared using 16S rRNA based Denaturant Gradient Gel Electrophoresis analysis. Diversity index revealed that Turbinaria sp hosts highest bacterial diversity while it was least in Gracilaria sp. The DGGE band profile showed that the epibacterial community differed considerably among the studied species. Statistical assessment using cluster analysis and Non-metric multidimensional scale analysis also authenticated the observed variability. Despite huge overlap, the composition of bacterial community structure differed significantly among the three closely related species namely Sargassum, Turbinaria and Padina. In addition, Enteromorpha and Sargassum, one being chlorophyta and the other phaeophyta showed about 80% similarity in bacterial composition. This differs from the general notion that epibacterial community composition will vary widely depending on the host phyla. The results extended the phenomenon of host specific epibacterial community irrespective of phylogeny and similarity in geographical location.
Indian journal of experimental biology 06/2015; 53(6):417-23. · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Group A streptococcus (GAS, Streptococcus pyogenes), a multi-virulent, exclusive human pathogen responsible for various invasive and non-invasive diseases possesses biofilm forming phenomenon as one of its pathogenic armaments. Recently, antibiofilm agents have gained prime importance, since inhibiting the biofilm formation is expected to reduce development of antibiotic resistance and increase their susceptibility to the host immune cells.
The current study demonstrates the antibiofilm activity of 3Furancarboxaldehyde (3FCA), a floral honey derived compound, against GAS biofilm, which was divulged using crystal violet assay, light microscopy, and confocal laser scanning microscopy. The report is extended to study its effect on various aspects of GAS (morphology, virulence, aggregation) at its minimal biofilm inhibitory concentration (132μg/ml). 3FCA was found to alter the growth pattern of GAS in solid and liquid medium and increased the rate of auto-aggregation. Electron microscopy unveiled the increase in extra polymeric substances around cell. Gene expression studies showed down-regulation of covR gene, which is speculated to be the prime target for the antibiofilm activity. Increased hyaluronic acid production and down regulation of srtB gene is attributed to the enhanced rate of auto-aggregation. The virulence genes (srv, mga, luxS and hasA) were also found to be over expressed, which was manifested with the increased susceptibility of the model organism Caenorhabditis elegans to 3FCA treated GAS. The toxicity of 3FCA was ruled out with no adverse effect on C. elegans.
Though 3FCA possess antibiofilm activity against GAS, it was also found to increase the virulence of GAS. This study demonstrates that, covR mediated antibiofilm activity may increase the virulence of GAS. This also emphasizes the importance to analyse the acclimatization response and virulence of the pathogen in the presence of antibiofilm compounds prior to their clinical trials.
PLoS ONE 05/2015; 10(5):e0127210. DOI:10.1371/journal.pone.0127210 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Emergence of extended antibiotic resistance among
bacterial pathogens often leads to the failure of existing antibiotics
to treat bacterial infections; therefore, there is an urgent
need to look for novel alternative treatment measures. The aim
of this study was to evaluate the anti-quorum sensing (QS)
potential of Synechococcus sp., to prevent the onset of bacterial
infections as an alternate to antibiotics. A total of 110
marine cyanobacterial strains were screened for their anti-QS
activity against biomarker strain Chromobacterium violaceum
(ATCC 12472) and aquatic bacterial pathogens Vibrio harveyi
(MTCC 3438) and Vibrio vulnificus (MTCC 1145). Of the 110
strains tested, the extract of unicellular algae Synechococcus
sp. (Q-25) exhibited the efficient reduction in the production
of violacein pigment of C. violaceum to the level of 82 %,
bioluminescence of V. harveyi to 91 % and protease in
V. vulnificus to 63 %. In V. harveyi and V. vulnificus, it exhibited
a significant reduction of 71 and 84 % in biofilm formation
and 66 and 68%in EPS production, respectively, without
any antibacterial activity. Confocal laser scanning microscopic
and light microscopic analyses further confirmed that the
Q-25 extract effectively prevented initial attachment as well as
disrupting the architecture of mature biofilm, when compared
to their untreated controls. In addition, the characterization of
active principle by gas chromatography–mass spectrometry
analysis confirmed the presence of stable bioactive compound
hexadecanoic acid in the extract. Hence, this study clearly
revealed the antibiofilm and QS inhibitory potential of the
cyanobacterium, Synechococcus sp.
Keywords Aquaculture . Vibriosis . Antibiotic resistance .
Quorum sensing . Cyanobacteria . Hexadecanoic acid
Journal of Applied Phycology 02/2015; DOI:10.1007/s10811-015-0554-0 · 2.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bacterial urinary tract infections (UTIs) are the most common nosocomial infections, accounting for about 40 % of all hospital-acquired infections. The bacterial spectrum of nosocomial UTIs is broad and the treatment of UTIs is becoming difficult owing to the emergence of drug resistance. Therefore, it is reasonable to investigate novel and alternative therapeutic strategies to treat UTIs. Since UTIs are caused by uropathogens with quorum sensing (QS)-dependent biofilm forming abilities, interruption of QS systems may be a novel approach to combat drug resistance. In the present study, a methanol extract (and hexane extract derived from it) of the medicinal plant Hyptis suaveolens (L.) were shown to have anti-QS activity against the biosensor strain Chromobacterium violaceum (ATCC 12472). Furthermore, the hexane extract of H. suaveolens (HEHS) inhibited biofilm formation by uropathogens such as Escherichia coli, Proteus vulgaris, Proteus mirabilis, Klebsiella pneumoniae and Serratia marcescens. HEHS promotes the loosening of biofilm architecture and strongly inhibits in vitro biofilm formation by uropathogens, which was more apparent from microscopic images. In addition to this, HEHS reduces the production of QS-dependent virulence factors like protease and hemolysin, along with motility. The partial purification and GC-MS analysis of the active fraction revealed the presence of several therapeutically important compounds which may synergistically act on the uropathogens and possibly reduce the QS-dependent phenotypes. These findings suggest HEHS as potential phytotherapeutic agent which can be employed to formulate protective strategies against biofilm linked infections caused by uropathogens.
Antonie van Leeuwenhoek 02/2015; 107(4). DOI:10.1007/s10482-015-0402-x · 1.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Coral Associated Bacteria (CAB) (N = 22) isolated from the mucus of the coral Acropora digitifera were screened for biosurfactants using classical screening methods; hemolysis test, lipase production, oil displacement, drop collapse test and emulsifying activity. Six CAB (U7, U9, U10, U13, U14, and U16) were found to produce biosurfactants and were identified by 16S ribosomal RNA gene sequencing as Providencia rettgeri, Psychrobacter sp., Bacillus flexus, Bacillus anthracis, Psychrobacter sp., and Bacillus pumilus respectively. Their cell surface hydrophobicity was determined by Microbial adhesion to hydrocarbon assay and the biosurfactants produced were extracted and characterized by Fourier Transform Infrared spectroscopy. Since the biosurfactants are known for their surface modifying capabilities, antibiofilm activity of positive isolates was evaluated against biofilm forming Pseudomonas aeruginosa ATCC10145. Stability of the active principle exhibiting antibiofilm activity was tested through various temperature treatments ranging from 60 to 100 °C and Proteinase K treatment. CAB isolates U7 and U9 exhibited stable antibiofilm activity even after exposure to higher temperatures which is promising for the development of novel antifouling agents for diverse industrial applications. Further, this is the first report on biosurfactant production by a coral symbiont.
Indian Journal of Microbiology 12/2014; 54(4). DOI:10.1007/s12088-014-0474-8 · 0.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Group A Streptococci (GAS) are involved in a number of life threatening diseases and biofilm formation by these pathogens are considered as an important virulence determinant as it mediates antibiotic resistance among them. In the present study, we have explored the ability of (+)-usnic acid, a lichen secondary metabolite, as an antibiofilm agent against four serotypes of Streptococcus pyogenes causing pharyngitis. Usnic acid inhibited the biofilms of M serotypes M56, st38, M89 efficiently and the biofilm of M74 to a lesser extent. Confocal imaging of the treated samples showed that usnic acid reduced the biomass of the biofilms when compared to that of the control. Fourier Transfer Infrared (FT-IR) spectroscopy indicated that usnic acid reduced the cellular components (proteins and fatty acids) of the biofilms. Interestingly, the FT-IR spectrum further revealed that usnic acid probably acted upon the fatty acids of the biofilms as evident from the disappearance of a peak at 2,455-2,100 cm(-1) when compared to the control only in serotypes M56, st38 and M89 but not in M74. The present study shows, for the first time, that usnic acid can act as an effective antibiofilm agent against GAS.
Antonie van Leeuwenhoek 11/2014; 107(1). DOI:10.1007/s10482-014-0324-z · 1.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Intercellular communication in bacteria (quorum sensing, QS) is an important phenomenon in disease dissemination and pathogenesis, which controls biofilm formation also. This study reports the anti-QS and anti-biofilm efficacy of seaweed Gracilaria gracilis associated Vibrio alginolyticus G16 against Serratia marcescens. Purification and mass spectrometric analysis revealed the active principle as phenol, 2,4-bis(1,1-dimethylethyl) [PD]. PD affected the QS regulated virulence factor production in S. marcescens and resulted in a significant (p < 0.05) reduction in biofilm (85%), protease (41.9%), haemolysin (69.9%), lipase (84.3%), prodigiosin (84.5%) and extracellular polysaccharide (84.62%) secretion without hampering growth, as evidenced by XTT [2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] assay. qPCR analysis confirmed the down-regulation of the fimA, fimC, flhD and bsmA genes involved in biofilm formation. Apart from biofilm inhibition and disruption, PD increased the susceptibility of S. marcescens to gentamicin when administered synergistically, which opens another avenue for combinatorial therapy where PD can be used to enhance the efficacy of conventional antibiotics.
[Show abstract][Hide abstract] ABSTRACT: A halotolerant α-amylase having the ability of digesting the insoluble raw starches was characterized from Bacillus subtilis S8-18, a marine sediment isolate from Palk Bay region. The electrophoresis techniques unveiled that the α-amylase was indeed a monomer with a molecular weight of 57 kDa. The optimum temperature and pH for the enzyme activity were 60 °C and 6.0 respectively. The enzyme was highly stable for 24 h over a wide range of pH from 4.0 to 12.0 by showing 84-94% activity. Interestingly, by retaining 72% activity even after 24 h, the enzyme also showed tolerance towards 28% NaCl. The α-amylase retained a minimum of 93% residual activity in 1 mM concentration for the selected divalent metal ions. The enzyme was found to be chelator resistant as it remained unaffected by 1 mM of EDTA and exhibited 96% activity even at 5 mM concentration. Furthermore, though 1% SDS caused remarkable reduction (68%) in amylase activity, the enzyme showed tolerance towards other detergents (1% of Triton-X and Tween 80) with 85% activity. Additionally, the α-amylase enzyme is capable of hydrolyzing the insoluble raw starch substrates which was evident from the scanning electron microscopic (SEM) and spectrophotometric analyses.
[Show abstract][Hide abstract] ABSTRACT: Since Streptococcus mutans is the principal etiologic agent causing dental caries, by encompassing an array of unique virulence traits, emerging treatment strategies that specifically target the virulence of this pathogen may be promising as alternative approaches compared to conventional antibiotic therapy. In this perspective, we investigated chloroform extract of cell-free culture supernatant from mangrove rhizosphere bacterium Bacillus amyloliquefaciens (MMS-50) in terms of anticariogenic properties of S. mutans, without suppressing its viability. Crude chloroform extract of MMS-50 was subjected to column and high performance liquid chromatographic techniques to obtain the active fraction (AF), and MMS-50 AF was used for all further assays. GC–MS and FT-IR were carried out to identify the major components present in MMS-50 AF. Comparative gene expression analysis of some biofilm-forming and virulence genes (vicR, comDE, gtfC, and gbpB) was done by real-time PCR. Cyclo(L-leucyl-L-prolyl) was found to be the chief compound in MMS-50 AF responsible for bioactivity. The minimum and maximum inhibitory concentrations of MMS-50 AF against S. mutans were found to be 100 and 250 μg/mL, respectively. Anti-virulence assays performed using below-sub-MIC levels of MMS-50 AF (30 μg/mL) resulted in significant reduction in adherence (68%), acid production, acid tolerance, glucan synthesis (32%), biofilm formation (53.5%) and cell surface hydrophobicity, all devoid of affecting its viability. The micrographs of CLSM and SEM further confirmed the antibiofilm and anti-virulence efficacies of MMS-50 AF. Expression data showed significant reduction in expression of all studied virulence genes. Thus, the current study unveils the anticariogenic potential of cyclo(L-leucyl-L-prolyl) from B. amyloliquefaciens, as well as its suitability as a novel and alternative anticariogenic agent against dental caries.
Research in Microbiology 05/2014; 165(4). DOI:10.1016/j.resmic.2014.03.004 · 2.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Urinary tract infection is caused primarily by the quorum sensing (QS)-dependent biofilm forming ability of uropathogens. In the present investigation, an anti-quorum sensing (anti-QS) agent curcumin from Curcuma longa (turmeric) was shown to inhibit the biofilm formation of uropathogens, such as Escherichia coli, Pseudomonas aeruginosa PAO1, Proteus mirabilis and Serratia marcescens, possibly by interfering with their QS systems. The antibiofilm potential of curcumin on uropathogens as well as its efficacy in disturbing the mature biofilms was examined under light microscope and confocal laser scanning microscope. The treatment with curcumin was also found to attenuate the QS-dependent factors, such as exopolysaccharide production, alginate production, swimming and swarming motility of uropathogens. Furthermore, it was documented that curcumin enhanced the susceptibility of a marker strain and uropathogens to conventional antibiotics.
[Show abstract][Hide abstract] ABSTRACT: The present study is aimed at developing an economical medium for the production of α-amylase from Bacillus subtilis S8-18, a marine sediment isolate from Palk Bay, with various agricultural by-products which are cheap and rich in starch. These products included wheat bran, wheat husk, rice bran, rice husk and potato peel and used to replace soluble starch present in the LB broth (synthetic medium). The rice husk was found to be the best to influence enzyme production significantly (61186 IU mL(-1) ) when compared to the yield of 30026 IU mL(-1) obtained by commercial starch. Hence, LB broth containing rice husk was termed as economical medium. Besides, the effect of various nutritional and physiological factors on enzyme production was also investigated. Furthermore, the desizing efficiency of α-amylases produced by synthetic and economical medium was evaluated through various assays like reducing sugar estimation, weight loss assay, drop absorbency assay, SEM and FTIR analyses. In addition, a commercial α-amylase from B. subtilis was also used in desizing analyses for comparative purpose. It revealed that the α-amylase from economical medium was highly effective in desizing the cotton fabrics as that of the commercial enzyme and much superior to the enzyme produced through synthetic medium. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Infectious diseases are of immediate concern due to their high rate of morbidity and mortality. Infectious diseases are life threatening in the current scenario as the causative agents are resistant to almost all the drugs in use. Apart from well-known factors like efflux pumps, receptor modifications, and drug inactivation, formation of biofilms attributes to broad-spectrum resistance toward antimicrobials. This necessitates the search for novel therapeutics that effectively control drug-resistant pathogens. Targeting biofilm formation is one such strategy to combat infectious diseases much more effectively. For over a decade diverse sources of synthetic to semisynthetic agents derived from microbes to plants have been tested for their antibiofilm potential with limited success. The birth of nanotechnology provided new insights into antibiofilm research as these nanoparticles are highly reactive and effective in penetrating the biofilm matrix. This chapter comprehensively summarizes the synthesis, application, weakness, and antibiofilm potential of nanoparticles.
[Show abstract][Hide abstract] ABSTRACT: Bacterial community composition in the marine environment differs from one geographical location to another. Reports that delineate the bacterial diversity of different marine samples from geographically similar location are limited. The present study aims to understand whether the bacterial community compositions from different marine samples harbour similar bacterial diversity since these are geographically related to each other.
In the present study, 16S rRNA deep sequencing analysis targeting V3 region was performed using Illumina bar coded sequencing. A total of 22.44 million paired end reads were obtained from the metagenomic DNA of Marine sediment, Rhizosphere sediment, Seawater and the epibacterial DNA of Seaweed and Seagrass. Diversity index analysis revealed that Marine sediment has the highest bacterial diversity and the least bacterial diversity was observed in Rhizosphere sediment. Proteobacteria, Actinobacteria and Bacteroidetes were the dominant taxa present in all the marine samples. Nearly 62-71% of rare species were identified in all the samples and most of these rare species were unique to a particular sample. Further taxonomic assignment at the phylum and genus level revealed that the bacterial community compositions differ among the samples.
This is the first report that supports the fact that, bacterial community composition is specific for specific samples irrespective of its similar geographical location. Existence of specific bacterial community for each sample may drive overall difference in bacterial structural composition of each sample. Further studies like whole metagenomic sequencing will throw more insights to the key stone players and its interconnecting metabolic pathways. In addition, this is one of the very few reports that depicts the unexplored bacterial diversity of marine samples (Marine sediment, Rhizosphere sediment, Seawater) and the host associated marine samples (Seaweed and Seagrass) at higher depths from uncharacterised coastal region of Palk Bay, India using next generation sequencing technology.
PLoS ONE 10/2013; 8(10):e76724. DOI:10.1371/journal.pone.0076724 · 3.23 Impact Factor