Potent Antibiofilm Agent Research Articles

Quorum Sensing Inhibitory Activities of Oridonin in Pseudomonas Aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen, and it can produce cell-associated and extracellular virulence factors. Several of these virulence factors have been demonstrated to be regulated by quorum sensing (QS). Disabling QS system with anti-infective agent is considered as a potential strategy to prevent bacterial infection. Rabdosia rubescens has been used as antibacterial agents for many centuries in China. In this study, Oridonin, the major active components of Rabdosia rubescens, was tested for QS inhibition in Pseudomonas aeruginosa. QS inhibitory activity is demonstrated by reduction in pyocyanin (58.4%), rhamnolipids (64.3%), elastase (58.6%), and protease (49.1%) in Pseudomonas aeruginosa PAO1 at 125 µg/ml (MIC) concentration. Biofilm formation by Pseudomonas aeruginosa PAO1 was reduced considerably (40.3-57.7%) over control. These findings suggest that Oridonin might be a potent Quorum Sensing Inhibitor (QSI) and anti-biofilm agent in the treatment of Pseudomonas aeruginosa infections.

AHL-Based QS Modulation and Inhibition of Biofilm Forming Foot Ulcer Pathogens by Selected Medicinal Plants

The crisis of antibiotic resistance necessitates the search of phytochemicals as potential antimicrobials, anti-quorum sensing and antibiofilm agents. For the present study, fifteen (15) medicinal plants were evaluated for biological activities against multi-drug resistant (MDR) pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis), associated with diabetic foot ulcer. Antibacterial activities revealed noteworthy minimum inhibitory concentration (MIC) values ≤ 1 mg/mL for thirteen (13) out of the sixty (60) plant extracts screened. The potent extracts included Euclea natalensis ethyl acetate (0.25 mg/mL), Aloe ferox methanol (0.5 mg/ml) and Warburgia salutaris aqueous (0.5 mg/mL) extracts. Chemical profiling of the active extracts using gas chromatography-mass spectrometry (GC-MS) identified neophytadiene, guanosine, squalene, cis megastigma-5,8-diene-4-one and sorbitol as prevalent compounds. Anti-quorum sensing activities of E. natalensis (ethyl acetate), A. ferox (methanol) and W. salutaris (aqueous) extracts ranged from 4.81 - 58.34% with E. natalensis (ethyl-acetate) showing the highest activity. Molecular docking against CviR protein showed selected compounds having high docking scores, with sorbitol showing the highest score of -7.04 kcal/mol. Warburgia salutaris aqueous extract exhibited the highest biofilm inhibition (73%) against E. coli. Euclea natalensis, Aloe ferox and Warburgia salutaris compounds act as antagonists of AHL signaling, thus may serve as candidates in antipathogenic and antibiofilm phytomedicine development for drug-resistant foot ulcer pathogens.

Octominin: An antibacterial and anti-biofilm peptide for controlling the multidrug resistance and pathogenic Streptococcus parauberis

Streptococcus parauberis is a pathogenic gram-positive bacterium that causes streptococcosis infection in fish. Since S. parauberis is becoming resistant to multiple antibiotics, the development of alternatives, such as antimicrobial peptides, has gained great attention. Octominin, derived from the defense protein of Octopus minor, showed a significant antimicrobial activity against multidrug resistance S. parauberis, with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 50 and 100 μg/mL, respectively. Furthermore, time-kill kinetics, agar diffusion, and bacterial viability assays confirmed the concentration-dependent antibacterial activity of Octominin against S. parauberis. Field emission scanning electron microscopy analysis showed morphological and ultra-structural changes in S. parauberis upon Octominin treatment. Moreover, Octominin treatment demonstrated changes in membrane permeability, induced reactive oxygen species (ROS), and its binding ability to genomic DNA, suggesting its strong bactericidal activity with multiple modes of action. We confirmed the inhibition of biofilm formation and the eradication of existing biofilms in a concentration-dependent manner. Additionally, Octominin on S. parauberis at transcriptional level exhibited downregulation of membrane formation (pgsA and cds1), DNA repairing (recF), biofilm formation (pgaB and epsF) genes, while upregulation of ROS detoxification (sodA) and DNA protecting (ahpF) related genes. An in vivo study confirmed a significantly (P < 0.05) higher relative percentage survival in Octominin-treated larval zebrafish exposed to S. parauberis (93.3%) compared to the control group (20.0%). Collectively, our results confirm that Octominin could be a potential antibacterial and anti-biofilm agent against S. parauberis.

Inhibition of biofilm and quorum sensing-regulated virulence factors in Pseudomonas aeruginosa by Cuphea carthagenensis (Jacq.) J. F. Macbr. Leaf extract: An in vitro study

Ethnopharmcological relevanceMicrobial biofilm formation, a quorum sensing (QS) regulated process, is one of the major causes of nosocomial and chronic infections, foodborne diseases, and associated deaths. Various approaches have been used to eradicate the menace of biofilm. Ethnomedicinal plants as potent antibiofilm agents are gaining a lot of interest in an era where the drug resistance is increasing and the availability of potent antibiotics is no longer promised. In this context, the methanol extract of Cuphea carthagenensis (CCMD), an ethno-medicinal and culinary herb, was evaluated as an antibiofilm and anti-QS agent against Pseudomonas aeruginosa.Aim of the study: The aim of the study is to evaluate the antibiofilm and anti-QS activity of an ethnomedicinal plant against a strong biofilm forming microorganism, P. aeruginosa. MethodsAntibiofilm activity of CCMD was demonstrated at different concentrations by Tissue Culture Plate, Test Tube method and other microscopic techniques. The effect of CCMD on QS and QS-related virulence factors viz. Pyocyanin, exopolymeric substance matrix (EPS), total protease, elastase, pyoverdin and swimming motility in P. aeruginosa were also evaluated. Antioxidant activity (DPPH & FRAP), total phenolic and flavonoid content were also checked. In order to determine the composition of the extract HPLC analysis was also performed. ResultsIn vitro study demonstrated a significant inhibition of biofilm formation (81.88 ± 2.57%) as well as production of QS-dependent virulence factors in P. aeruginosa. The extract also inhibited violacein production (83.31 ± 2.77%) in Chromobacterium violaceum which correlates with the reduction in QS-mediated virulence factors. The extract showed 64.79% ± 0.83% DPPH scavenging activity and reduction of ferricyanide complex (Fe3+) to the ferrous form (Fe2+) in DPPH and FRAP assay, respectively. Furthermore, the extract showed thermal stability and does not have any growth inhibitory effect on P. aeruginosa. The HPLC analysis demonstrated the presence of ellagic acid, ascorbic acid and hippuric acid in the extract. ConclusionThis work is the first to demonstrate that C. carthagenensis can attenuate biofilm formation and QS-mediated virulence factors of P. aeruginosa. Further investigation is required to use this ethnomedicinal plant (CCMD) as an important source of antibiofilm agents.

Laser-Irradiated Chlorpromazine as a Potent Anti-Biofilm Agent for Coating of Biomedical Devices

Nowadays, antibiotic resistance has become increasingly common, triggering a global health crisis, immediately needing alternative, including repurposed drugs with potent bactericidal effects. We demonstrated that chlorpromazine aqueous solutions exposed to laser radiation exhibited visible activity against various microorganisms. The aim of this study was to investigate the quantitative antimicrobial activity of chlorpromazine in non-irradiated and 4-h laser irradiated form. Also, we examined the effect of both solutions impregnated on a cotton patch, cannula, and urinary catheter against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli. In all experimental versions, the chlorpromazine antimicrobial activity was enhanced by laser exposure. Besides the experimental results, the in silico analyses using molecular docking proved that the improved antimicrobial activity of the irradiated compound was a result of the combined action of the photoproducts on the biological target (s). Our results show that laser radiation could alter the molecular structure of various drugs and their effects, proving to be a promising strategy to halt antibiotic resistance, by repurposing current medicines for new antimicrobial strategies, thereby decreasing the costs and time for the development of more efficient drugs.

ANTIFUNGAL AND ANTIBIOFILM ACTIVITY OF 2-BROMO-N-PHENYLCETAMIDE AGAINST CRYPTOCOCCUS NEOFORMANS

Objective: This study aimed to evaluate the antifungal and antibiofilm of 2-bromo-N-phenylacetamide (A1Br) against Cryptococcus neoformans in vitro.&#x0D; Methods: The compound was characterized by infrared and 1H-nuclear magnetic resonance spectrometry data. Minimum inhibitory concentration (MIC) was determined using the plate dilution method and biofilm formation inhibition of the crystal violet assay.&#x0D; Results: A1Br inhibited the growth of C. neoformans with MIC of 0.25 and 0.5 μg/ml and has good antibiofilm activity MIC ×4, with ≥80% inhibition growth.&#x0D; Conclusions: Thus, A1Br shows potential antifungal and antibiofilm agents for the treatment of infections caused by C. neoformans, as well as the eradication of cryptococcal colonization of medical prosthetic devices.

Purification, characterization, and mode of action of a novel bacteriocin BM173 from Lactobacillus crustorum MN047 and its effect on biofilm formation of Escherichia coli and Staphylococcus aureus

There is an increasing demand for dairy products, but the presence of food-spoilage bacteria seriously affects the development of the dairy industry. Bacteriocins are considered to be a potential antibacterial or antibiofilm agent that can be applied as a preservative. In this study, bacteriocin BM173 was successfully expressed in the Escherichia coli expression system and purified by a 2-step method. Furthermore, it exhibited a broad-spectrum antibacterial activity, high thermal stability (121°C, 20 min), and broad pH stability (pH 3-11). Moreover, the minimum inhibitory concentration values of BM173 against E. coli ATCC 25922 and Staphylococcus aureus ATCC 25923 were 14.8 μg/mL and 29.6 μg/mL, respectively. Growth and time-kill curves showed that BM173 exhibited antibacterial and bactericidal activity. The results of scanning electron microscopy and transmission electron microscopy demonstrated that BM173 increased membrane permeability, facilitated pore formation, and even promoted cell lysis. The disruption of cell membrane integrity was further verified by propidium iodide uptake and lactic dehydrogenase release. In addition, BM173 exhibited high efficiency in inhibiting biofilm formation. Therefore, BM173 has promising potential as a preservative used in the dairy industry.

Inhibitory effect of Newtonia extracts and myricetin-3-o-rhamnoside (myricitrin) on bacterial biofilm formation

BackgroundDiarrhoea is a major health issue in both humans and animals and may be caused by bacterial, viral and fungal infections. Previous studies highlighted excellent activity of Newtonia buchananii and N. hildebrandtii leaf extracts against bacterial and fungal organisms related to diarrhoea-causing pathogens. The aim of this study was to isolate the compound(s) responsible for antimicrobial activity and to investigate efficacy of the extracts and purified compound against bacterial biofilms.MethodsThe acetone extract of N. buchananii leaf powder was separated by solvent-solvent partitioning into eight fractions, followed by bioassay-guided fractionation for isolation of antimicrobial compounds. Antibacterial activity testing was performed using a broth microdilution assay. The cytotoxicity was evaluated against Vero cells using a colorimetric MTT assay. A crystal violet method was employed to test the inhibitory effect of acetone, methanol: dichloromethane and water (cold and hot) extracts of N. buchananii and N. hildebrandtii leaves and the purified compound on biofilm formation of Pseudomonas aeruginosa, Escherichia coli, Salmonella Typhimurium, Enterococcus faecalis, Staphylococcus aureus and Bacillus cereus.ResultsMyricetin-3-o-rhamnoside (myricitrin) was isolated for the first time from N. buchananii. Myricitrin was active against B. cereus, E. coli and S. aureus (MIC = 62.5 μg/ml in all cases). Additionally, myricitrin had relatively low cytotoxicity with IC50 = 104 μg/ml. Extracts of both plant species had stronger biofilm inhibitory activity against Gram-positive than Gram-negative bacteria. The most sensitive bacterial strains were E. faecalis and S. aureus. The cold and hot water leaf extracts of N. buchananii had antibacterial activity and were relatively non-cytotoxic with selectivity index values of 1.98–11.44.ConclusionsThe purified compound, myricitrin, contributed to the activity of N. buchananii but it is likely that synergistic effects play a role in the antibacterial and antibiofilm efficacy of the plant extract. The cold and hot water leaf extracts of N. buchananii may be developed as potential antibacterial and antibiofilm agents in the natural treatment of gastrointestinal disorders including diarrhoea in both human and veterinary medicine.

Anti-biofilm compound of 1, 4-diaza-2, 5-dioxo-3-isobutyl bicyclo[4.3.0]nonane from marine Nocardiopsis sp. DMS 2 (MH900226) against biofilm forming K. pneumoniae

In this study, the 16S rRNA of the marine endophytic actinomycete was characterized and identified as Nocardiopsis sp. strain DMS 2 (MH900226). Partial purification and spectroscopies data were interpreted and confirmed as 1, 4-diaza-2, 5-dioxo-3-isobutyl bicyclo[4.3.0]nonane. Anti-bacterial activity of the crude extract and partially purified compound were shown highest inhibition activity against biofilm forming K. pneumoniae. Minimum biofilm inhibition concentration of identified compound against K. pneumoniae was exhibited at the concentration of 300 µg/mL. Decreased metabolic activity and modified exopolysaccharide production of biofilm forming cells were observed at 350 µg/mL and 300 µg/mL concentration. At the same biofilm inhibition concentration, the intracellular architecture of the biofilm cells and extracellular shape modifications were clearly viewed by confocal laser scanning electron microscope and scanning electron microscope respectively. All the in-vitro inhibition results and microscopic images were strongly suggested that the identified compound was a potential anti-biofilm agent against tested K. pneumoniae.

Antibacterial and cytotoxicity activities of biosynthesized silver oxide (Ag2O) nanoparticles using Bacillus paramycoides

Bionanotechnology is one of the leading research which helps to synthesize nanoparticles through biological resources. In the present study silver oxide nanoparticles (Ag2O NPs) were biosynthesized using culture supernatant of Bacillus paramycoides and evaluated for its antibiofilm activity and cytotoxic potentiality. Characteristic absorption peak for Ag2O NPs was observed at 420 nm in UV–visible spectrum. X-ray diffraction pattern shows planes of face centered cubic crystalline Ag2O NPs and narrow peak confirms their crystalline nature. High Resolution Transmission Electron Microscopy exhibited spherical particles in the range of 25–70 nm diameter. Fourier transform infrared spectroscopic analysis of Ag2O NPs represents the peaks corresponding to the functional groups of metabolites present in the supernatant. The biosynthesized Ag2O NPs showed significant antibacterial activity against marine biofilm forming bacteria (Vibrio parahaemolyticus, Salmonella sp., Enterobacter sp. and Micrococcus sp.) as observed under confocal laser scanning microscope. The present study revealed that Ag2O NPs cause release of intracellular constituents including proteins through membrane damage leading to the bacterial cell death. Silver oxide nanoparticles also showed significant cytotoxicity on A549 lung cancer cells (IC50 = 58.5 μg mL−1) by MTT assay. A549 cells treated with Ag2O NPs showed signs of apoptosis as observed under fluorescent microscope. The present study highlights the possible use of Ag2O NPs as potential antibacterial, antibiofilm and anticancer agent.

Promising Antibiofilm Agents: Recent Breakthrough against Biofilm Producing Methicillin-Resistant Staphylococcus aureus.

Multidrug resistant (MDR) methicillin-resistant Staphylococcus aureus (MRSA) is a superbug pathogen that causes serious diseases. One of the main reasons for the lack of the effectiveness of antibiotic therapy against infections caused by this resistant pathogen is the recalcitrant nature of MRSA biofilms, which results in an increasingly serious situation worldwide. Consequently, the development of innovative biofilm inhibitors is urgently needed to control the biofilm formation by this pathogen. In this work, we thus sought to evaluate the biofilm inhibiting ability of some promising antibiofilm agents such as zinc oxide nanoparticles (Zno NPs), proteinase K, and hamamelitannin (HAM) in managing the MRSA biofilms. Different phenotypic and genotypic methods were used to identify the biofilm producing MDR MRSA isolates and the antibiofilm/antimicrobial activities of the used promising agents. Our study demonstrated strong antibiofilm activities of ZnO NPs, proteinase K, and HAM against MRSA biofilms along with their transcriptional modulation of biofilm (intercellular adhesion A, icaA) and quorum sensing (QS) (agr) genes. Interestingly, only ZnO NPs showed a powerful antimicrobial activity against this pathogen. Collectively, we observed overall positive correlations between the biofilm production and the antimicrobial resistance/agr genotypes II and IV. Meanwhile, there was no significant correlation between the toxin genes and the biofilm production. The ZnO NPs were recommended to be used alone as potent antimicrobial and antibiofilm agents against MDR MRSA and their biofilm-associated diseases. On the other hand, proteinase-K and HAM can be co-administrated with other antimicrobial agents to manage such types of infections.

Glabridin Averts Biofilms Formation in Methicillin-Resistant Staphylococcus aureus by Modulation of the Surfaceome.

Staphylococcus aureus is an opportunistic bacterium of the human body and a leading cause of nosocomial infections. Methicillin resistant S. aureus (MRSA) infections involving biofilm lead to higher mortality and morbidity in patients. Biofilm causes serious clinical issues, as it mitigates entry of antimicrobials to reach the etiological agents. It plays an important role in resilient chronic infections which place an unnecessary burden on antibiotics and the associated costs. To combat drug-resistant infection involving biofilm, there is a need to discover potential anti-biofilm agents. In this study, activity of polyphenolic flavonoid glabridin against biofilm formation of methicillin resistant clinical isolates of S. aureus is being reported for the first time. Crystal violet assay and scanning electron microscopy evidences shows that glabridin prevents formation of cells clusters and attachment of methicillin resistant clinical isolate (MRSA 4423) of S. aureus to the surface in a dose dependent manner. Gel free proteomic analysis of biofilm matrix by LC-ESI-QTOF confirmed the existence of several proteins known to be involved in cells adhesion. Furthermore, expression analysis of cell surface proteins revealed that glabridin significantly down regulates an abundance of several surface-associated adhesins including fibronectin binding proteins (FnbA, FnbB), serine-aspartate repeat-containing protein D (SdrD), immunoglobulin-binding protein G (Sbi), and other virulence factors which were induced by extracellular glucose in MRSA 4423. In addition, several moonlighting proteins (proteins with multiple functions) such as translation elongation factors (EF-Tu, EF-G), chaperone protein (DnaK), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) were detected on the cell surface wherein their abundance was inversely proportional to surface-associated adhesins. This study clearly suggests that glabridin prevents biofilm formation in S. aureus through modulation of the cell surface proteins.

A Fluorinated Analogue of Marine Bisindole Alkaloid 2,2-Bis(6-bromo-1H-indol-3-yl)ethanamine as Potential Anti-Biofilm Agent and Antibiotic Adjuvant Against Staphylococcus aureus.

Methicillin resistant Staphylococcus aureus (MRSA) infections represent a major global healthcare problem. Therapeutic options are often limited by the ability of MRSA strains to grow as biofilms on medical devices, where antibiotic persistence and resistance is positively selected, leading to recurrent and chronic implant-associated infections. One strategy to circumvent these problems is the co-administration of adjuvants, which may prolong the efficacy of antibiotic treatments, by broadening their spectrum and lowering the required dosage. The marine bisindole alkaloid 2,2-bis(6-bromo-1H-indol-3-yl)ethanamine (1) and its fluorinated analogue (2) were tested for their potential use as antibiotic adjuvants and antibiofilm agents against S. aureus CH 10850 (MRSA) and S. aureus ATCC 29213 (MSSA). Both compounds showed antimicrobial activity and bisindole 2 enabled 256-fold reduction (ΣFICs = 0.5) in the minimum inhibitory concentration (MIC) of oxacillin for the clinical MRSA strain. In addition, these molecules inhibited biofilm formation of S. aureus strains, and compound 2 showed greater eradicating activity on preformed biofilm compared to 1. None of the tested molecules exerted a viable but non-culturable cells (VBNC) inducing effect at their MIC values. Moreover, both compounds exhibited no hemolytic activity and a good stability in plasma, indicating a non-toxic profile, hence, in particular compound 2, a potential for in vivo applications to restore antibiotic treatment against MRSA infections.

Silver decorated green nanocolloids as potent antibacterial and antibiofilm agent against antibiotic resistant organisms isolated from tannery effluent

Pollution is caused because of poor disposal of solid and liquid waste from the leather industry and release 20% of treated effluent and while the rest of 80% is untreated. The tannery effluent is a house for many antibiotic resistant bacteria and multi-drug resistant bacteria and these bacteria cause various bacterial infections which cannot be treated by antibiotics. This current work is focused on isolation and identification of antibiotic resistant strains from tannery effluent. To eliminate the antibiotic resistant strains from tannery effluent and make it beneficial to the society, green nanocolloid was synthesized from traditional medicinal plant Andographis paniculata. Various physio-chemical characterizations such as UV-Vis spectrum, FT-IR spectrum, Particle size analysis, Zeta potential analysis, FE-SEM and elemental analysis using EDAX were employed to identify the characteristic nature of green silver nanocolloids. Antibacterial and antibiofilm assays were performed to validate the efficacy of green nanocolloids. The results showed that ApNc had potent Antibacterial and antibio-film activity against antibiotic resistant strains isolated from tannery effluent. These green nanocolloids could be the alternate source to eradicate antibiotic resistant strains thriving in the tannery effluent. In future this formulation can be employed as a nanospary to avoid the spread of antibiotic resistant strains entering into human and animal system. This research work has been undertaken for the benefit of the society to provide people with better resources and to establish an environment that is disease free and eco-friendly.

Synergistic antibacterial and anti-biofilm activity of nisin like bacteriocin with curcumin and cinnamaldehyde against ESBL and MBL producing clinical strains

Bacteriocins are small peptides that can inhibit the growth of a diverse range of microbes. There is a need to identify bacteriocins that are effective against biofilms of resistant clinical strains. The present study focussed on the efficacy of purified nisin like bacteriocin-GAM217 against extended spectrum β-lactamase (ESBL) and metallo-beta-lactamase (MBL) producing clinical strains. Bacteriocin-GAM217 when combined with curcumin and cinnamaldehyde, synergistically enhanced antibacterial activity against planktonic and biofilm cultures of Staphylococcus epidermidis and Escherichia coli. Bacteriocin-GAM217 and phytochemical combinations inhibited biofilm formation by >80%, and disrupted the biofilm for selected ESBL and MBL producing clinical strains. The anti-adhesion assay showed that these combinatorial compounds significantly lowered the attachment of bacteria to Vero cells and that they elicited membrane permeability and rapid killing as viewed by confocal microscopy. This study demonstrates that bacteriocin-GAM217 in combination with phytochemicals can be a potential anti-biofilm agent and thus has potential for biomedical applications.

Silver nanoparticles: A potential antibacterial and antibiofilm agent against biofilm forming multidrug resistant bacteria

Multi-drug resistant (MDR) bacteria are seriously endangering the antibiotics. Different alternative strategies are needed to reinforce antibiotics, of, these; nanostructured materials may play a fruitful role. This study aimed to investigate the antibacterial and antibiofilm activity of silver nanoparticles (AgNPs) against MDR bacteria. Methods: In a cross-sectional study, a total of 33 methicillin resistant Staphylococcus aureus (MRSA) and 52 MDR Pseudomonas aeruginosa (P. aeruginosa) isolates were recovered from intensive care units’ (ICUs) admitted patients over a period of 9 months, from December 2017 to August 2018. The antibacterial activity of AgNPs on the clinical isolates of MRSA and MDR P. aeruginosa was assessed by minimum inhibitory concentrations (MICs) using broth microdilution method. The minimum bactericidal concentrations (MBCs) were determined as the lowest concentrations required to kill 99.9% of the initial inoculum. Tissue culture plate method was used to evaluate the antibiofilm activity. Results: The MIC and MBC values ranged from 1 to 16 μg/ml and 2 to 64 μg/ml, respectively. Silver nanoparticles exerted a significant antibiofilm activity against MRSA and MDR P.aeruginosa at all tested concentrations, recording a maximum inhibition value of (82%) and (91%), respectively. Conclusions: AgNPs exhibited a considerable antibacterial and antibiofilm, effect; it could represent a promising weapon in the fight against biofilm forming MDR organisms.

An Optimized Anti-adherence and Anti-biofilm Assay: Case Study of Zinc Oxide Nanoparticles versus MRSA Biofilm

Biofilms form protective layers over bacteria that are associated with a majority of the hospital infections contributing to antibiotic resistance development in susceptible strains. Nowadays, there is a pressing need for developing effective anti-biofilm agents to help address the growing problem of biofilm-producing bacteria associated with antibiotic resistance. In recent years, zinc oxide nanoparticles (ZnO-NPs) has emerged as a prospective candidate for new anti-biofilm agents. The present method paper described an optimized anti-adherence and anti-biofilm assay using ZnO-NPs. The antibiotic-resistant bacteria Methicillin-resistant Staphylococcus aureus (MRSA ATCC4330) and vancomycin were used as the growth control and positive control, respectively. The result showed concentration-dependent anti-adherence and antibiofilm activity. The ZnO-NPs effectively prevented attachment of bacterial cells onto walls of wells with 51.69 ± 2.55% at the highest concentration tested (65.4 µg/mL). ZnO-NPs was also able to break-up 50% pre-formed MRSA biofilm at the lowest concentration of 13.5 µg/mL. Interestingly, ZnO-NPs at lower concentrations demonstrated significantly stronger antibiofilm activity than that of the positive control vancomycin, demonstrating that ZnO-NPs is a promising anti-biofilm agent. This method could be used as a preliminary screening of transition metal oxide nanoparticles as potential anti-adherence and anti-biofilm agents followed by other specific anti-biofilm assays.

Exploring antibiofilm potential of bacitracin against streptococcus mutans

Bacitracin has well familiar effects on growth and colonization of bacteria but its antibiofilm action on majority of bacteria is still not studied. Bacitracin is a bactericidal antibiotic that primarily acts on Gram positive bacteria by obstructing the process of cell wall synthesis. In this study, we have investigated antibiofilm potential and the mechanism of bacitracin against a cariogenic bacteria ‘Streptococcus mutans’ which has not been reported so far. Bacitracin has been found to affect propensity of S. mutans to form biofilm. On treatment with sub-MIC concentration of bacitracin resulted in significant reduction in bifilm formation as evaluated by crystal violet and congo red assays. The architecture of S. mutans biofilm was observed by scanning electron microscopy which revealed astonishing phenotype of biofilm. Deficient biofilm was found to be composed of abnormally elongated cells. Transmission electron microscopy showed multiple septa formation in each cell of biofilm thereby indicating, cell division defect as the most probable cause of cell elongation. To elucidate the effect of bacitracin on molecular level, expression profiling of genes critically important for cell division and biofilm formation was performed, which were found many folds downregulated. Bacitracin at very low concentration has been found to have potent antibiofilm activity, therefore is a potential antibiofilm agent to treat oral biofilms. It is being anticipated, this study will offer novel information to identify potential targets and effectively creates true innovation to understand the biofilm's basic biology. Besides, discovering new uses for currently marketed drugs makes commercial as well as research sense.

Evaluation of antibiofilm efficacy of essential oil components β-caryophyllene, cinnamaldehyde and eugenol alone and in combination against biofilm formation and preformed biofilms of Listeria monocytogenes and Salmonella typhimurium.

The aim of this study was to examine whether the process of initial colonization and the formation of mature biofilm structure of foodborne bacterial pathogens Listeria monocytogenes and Salmonella typhimurium can be impeded by active essential oil components β-caryophyllene, cinnamaldehyde and eugenol at their individual and combined effects. Among the essential oil components tested, cinnamaldehyde and eugenol at their individual effect showed >50% degradation in biofilm biomass against preformed (matured) biofilms of both the studied bacteria, whereas β-caryophyllene failed to do so. In combination, cinnamaldehyde/eugenol blend showed synergistic antibiofilm efficacy against preformed biofilms of both the studied bacteria L. monocytogenes (FICI: 0·24) and S. typhimurium (FICI: 0·40), whereas other tested combinations showed additive antibiofilm efficacy with FICI ranged from 2·02 to 2·35. Essential oil components alone and in combination also showed much higher inhibition effect on biofilm formation at the initial stage compared to their inhibition effect on preformed biofilms. The results provide evidence that cinnamaldehyde/eugenol combination may help in designing a more potent novel, natural antibiofilm blend at sufficiently low concentrations in the food and pharmaceutical industries. SIGNIFICANCE AND IMPACT OF THE STUDY: In the present work, synergistic antibiofilm efficacy of cinnamaldehyde/eugenol combination against established biofilms of foodborne bacterial pathogens Listeria monocytogenes and Salmonella typhimurium has been reported. These synergistic interactions may help in designing a more potent, safe and effective novel natural antibiofilm agent in food and pharmaceutical industries. Besides, this combination will also be helpful in reducing concentration of individual components, thereby minimizing the undesirable impact on sensory properties of food. To our knowledge, this is the first time, synergistic antibiofilm efficacy of cinnamaldehyde/eugenol blend against established biofilms of foodborne bacterial pathogens has been reported.

Cannabigerol Prevents Quorum Sensing and Biofilm Formation of Vibrio harveyi.

Cannabigerol (CBG) is a non-psychoactive cannabinoid naturally present in trace amounts in the Cannabis plant. So far, CBG has been shown to exert diverse activities in eukaryotes. However, much less is known about its effects on prokaryotes. In this study, we investigated the potential role of CBG as an anti-biofilm and anti-quorum sensing agent against Vibrio harveyi. Quorum sensing (QS) is a cell-to-cell communication system among bacteria that involves small signaling molecules called autoinducers, enabling bacteria to sense the surrounding environment. The autoinducers cause alterations in gene expression and induce bioluminescence, pigment production, motility and biofilm formation. The effect of CBG was tested on V. harveyi grown under planktonic and biofilm conditions. CBG reduced the QS-regulated bioluminescence and biofilm formation of V. harveyi at concentrations not affecting the planktonic bacterial growth. CBG also reduced the motility of V. harveyi in a dose-dependent manner. We further observed that CBG increased LuxO expression and activity, with a concomitant 80% downregulation of the LuxR gene. Exogenous addition of autoinducers could not overcome the QS-inhibitory effect of CBG, suggesting that CBG interferes with the transmission of the autoinducer signals. In conclusion, our study shows that CBG is a potential anti-biofilm agent via inhibition of the QS cascade.