Biofilm Formation Of Pathogenic Bacteria Research Articles

Neem Leaves Extract (Azadirachta indica) and Its Bactericidal Activity against Biofilm-forming Pathogenic Bacteria

Antibiotics are used in healthcare as for prophylaxis and have therapeutic value against drug-resistant bacteria. The main aim of the study was to analyze the potential of neem leaf extract against pathogenic bacteria. The leaves were dried and phytochemicals were extracted with methanol, ethyl acetate, chloroform, and water. The methanol extract showed maximum yield. The total phenolic and flavonoid contents were found to be maximum in methanol extract. The methanol extract showed maximum activity followed by ethyl acetate, chloroform, and water. The methanol extract exhibited maximum activity against Enterobacter aerogenes (18±2 mm zone of inhibition), Salmonella typhimurium (16±1 mm zone of inhibition), Pseudomonas aeruginosa (20±2 mm zone of inhibition), Staphylococcus aureus (12±0 mm zone of inhibition), and Escherichia coli (20±0 mm) (p<0.05). The minimum inhibitory concentration values ranged from 6.25±1.25 to 300±125 µg/ml and methanol extract showed least value against bacteria (p<0.05).

Molecular Aspects of the Functioning of Pathogenic Bacteria Biofilm Based on Quorum Sensing (QS) Signal-Response System and Innovative Non-Antibiotic Strategies for Their Elimination.

One of the key mechanisms enabling bacterial cells to create biofilms and regulate crucial life functions in a global and highly synchronized way is a bacterial communication system called quorum sensing (QS). QS is a bacterial cell-to-cell communication process that depends on the bacterial population density and is mediated by small signalling molecules called autoinducers (AIs). In bacteria, QS controls the biofilm formation through the global regulation of gene expression involved in the extracellular polymeric matrix (EPS) synthesis, virulence factor production, stress tolerance and metabolic adaptation. Forming biofilm is one of the crucial mechanisms of bacterial antimicrobial resistance (AMR). A common feature of human pathogens is the ability to form biofilm, which poses a serious medical issue due to their high susceptibility to traditional antibiotics. Because QS is associated with virulence and biofilm formation, there is a belief that inhibition of QS activity called quorum quenching (QQ) may provide alternative therapeutic methods for treating microbial infections. This review summarises recent progress in biofilm research, focusing on the mechanisms by which biofilms, especially those formed by pathogenic bacteria, become resistant to antibiotic treatment. Subsequently, a potential alternative approach to QS inhibition highlighting innovative non-antibiotic strategies to control AMR and biofilm formation of pathogenic bacteria has been discussed.

Assessment of polarized piezoelectric SrBi4Ti4O15 nanoparticles as alternative antibacterial agents

Nanoparticles of strontium bismuth titanate (SrBi4Ti4O15/SBT NPs), along with their polarized counterparts, were prepared and their ability to combat bacterial growth on the surface of biomaterials was assessed. The structural properties of the SBT NPs were analyzed using X-ray diffraction, and their effectiveness against Staphylococcus aureus pathogenic bacteria was evaluated. While the 30 h bacteria culture results showed that the bacteria were entirely destroyed by the polarized SBT, only 24 % of the bacteria were destroyed by the unpolarized specimens The results showed that polarized SBT was significantly effective against Staphylococcus aureus bacteria, and can effectively combat bacterial growth and prevent biofilm formation of pathogenic bacteria. Hence, it can be considered as an alternative antimicrobial agent.

Surface grafting of polymeric catheters and stents to prevent biofilm formation of pathogenic bacteria

BackgroundTecothane (medical grade of polyurethane) is strongly involved in the fabrication of metallic and polymeric-based medical devices (e.g., catheters and stents) as they can withstand cardiac cycle-related forces without deforming or failing, and they can mimic tissue behavior. The main problem is microbial contamination and formation of pathogenic biofilms on such solid surfaces within the human body. Accordingly, our hypothesis is the coating of tecothane outer surfaces with antibacterial agents through the electro-deposition or chemical grafting of anti-biofilm agents onto the stent and catheter surfaces. ResultsTecothane is grafted with itaconic acid for cross-linking the polyethyleneimine (PEI) as the protective-active layer. Accordingly, the grafting of poly-itaconic acid onto the Tecothane was achieved by three different methods: wet-chemical approach, electro-polymerization, or by using plasma treatment. The successful modifications were verified using Fourier Transform Infrared (FTIR) spectroscopy, grafting percentage calculations, electrochemical, and microscopic monitoring of biofilm formation. The grafting efficiency of itaconic acid was over 3.2% (w/w) at 60 ℃ after 6 h of the catheter chemical modification. Bio-electrochemical signals of biofilms have been seriously reduced after chemical modification because of the inhibition of biofilm formation (for both Pseudomonas aeruginosa and Staphylococcus aureus) over a period of 9 days. ConclusionChemical functionalization of the polyurethane materials with the antimicrobial and anti-biofilm agents led to a significant decrease in the formation of pathogenic biofilms. This promising proof-concept will open the door to explore further surface protection with potential anti-biofilm agents providing better and sustainable productions of stents and catheters biomaterials. Graphical Abstract▪

Antibacterial Activity of Boron Compounds Against Biofilm-Forming Pathogens.

This study aimed to evaluate the antibacterial activity of nine boron derivatives against biofilm-forming pathogenic bacteria. The effect of boron derivatives (CMB, calcium metaborate; SMTB, sodium metaborate tetrahydrate; ZB, zinc borate; STFB, sodium tetra fluorine borate; STB, sodium tetraborate; PTFB, potassium tetra fluor borate; APTB, ammonium pentabo-rate tetrahydrate; SPM, sodium perborate monohydrate; Borax, ATFB, ammonium tetra fluorine borate) on bacteria isolated from blood culture was determined by the minimum inhibitory concentration (MIC) method. Then, biofilm formation potentials on microplates, tubes, and Congo red agar were examined. The cytotoxicity of boron derivatives was determined by using WST-1-based methods. The interaction between the biofilm-forming bacteria, fibroblast cells, and boron derivatives was determined with the infection model. We found that the sodium metaborate tetrahydrate molecule was effective against all pathogens. According to the optical density values detected at 630nm in microplates, meticillin-resistant Staphylococcus aureus was observed to have the most substantial biofilm ability at 0.257nm. As a result of cytotoxicity studies, it has been determined that a 1µg/L concentration of boron derivatives is not toxic to fibroblast L929 cells. In cell culture experiments, these boron derivatives have very serious inhibitory activity against biofilm-forming pathogens in a short treatment period, such as 2-4h. Furthermore, using these molecules on inanimate surfaces affected by biofilms would be appropriate instead of living cells.

Effects of Repeated in-vitro Exposure to Saudi Honey on Bacterial Resistance to Antibiotics and Biofilm Formation.

Although Sumra and Sidr Saudi honey is widely used in traditional medicine due to its potent activity, it is unknown whether its prolonged usage has impact upon bacterial virulence or leading to reduced antibiotic sensitivity. Thus, the study aims to investigate the effect of prolonged (repeated) in-vitro exposure to Saudi honey on the antibiotic susceptibility profiles and biofilm formation of pathogenic bacteria. Several bacteria, including Staphylococcus aureus, Escherichia coli, and Acinetobacter baumannii, were in-vitro exposed ten times [passaged (P10)]to Sumra and Sider honey individually to introduce adapted bacteria (P10). Antibiotic susceptibility profiles of untreated (P0) and adapted (P10) bacteria were assessed using disc diffusion and microdilution assays. The tendency regarding biofilm formation following in-vitro exposure to honey (P10) was assessed using the Crystal violet staining method. Adapted (P10) bacteria to both Sumra and Sidr honey showed an increased sensitivity to gentamicin, ceftazidime, ampicillin, amoxycillin/clavulanic acid, and ceftriaxone, when compared with the parent strains (P0). In addition, A. baumannii (P10) that was adapted to Sidr honey displayed a 4-fold increase in the minimal inhibitory concentration of the same honey following in-vitro exposure. 3-fold reduction in the tendency toward biofilm formation was observed for the Sumra-adapted (P10) methicillin resistant S. aureus strain, although there was a lower rate of reduction (1.5-fold) in biofilm formation by both the Sumra- and Sidr-adapted A. baumannii (P10) strains. The data highlight the positive impact of prolonged in-vitro exposure to Saudi honey (Sumra and Sider) for wound-associated bacteria since they displayed a significant increase in their sensitivity profiles to the tested antibiotic and a reduction in their ability to form biofilm. The increased bacterial sensitivity to antibiotics and a limited tendency toward biofilm formation would suggest the great potential therapeutic use of this Saudi honey (Sumra and Sidr) to treat wound infections.

Effect of Essential Oil from Lippia origanoides on the Transcriptional Expression of Genes Related to Quorum Sensing, Biofilm Formation, and Virulence of Escherichia coli and Staphylococcus aureus.

Microbial infections resistant to conventional antibiotics constitute one of the most important causes of mortality in the world. In some bacterial species, such as Escherichia coli and Staphylococcus aureus pathogens, biofilm formation can favor their antimicrobial resistance. These biofilm-forming bacteria produce a compact and protective matrix, allowing their adherence and colonization to different surfaces, and contributing to resistance, recurrence, and chronicity of the infections. Therefore, different therapeutic alternatives have been investigated to interrupt both cellular communication routes and biofilm formation. Among these, essential oils (EO) from Lippia origanoides thymol-carvacrol II chemotype (LOTC II) plants have demonstrated biological activity against different biofilm-forming pathogenic bacteria. In this work, we determined the effect of LOTC II EO on the expression of genes associated with quorum sensing (QS) communication, biofilm formation, and virulence of E. coli ATCC 25922 and S. aureus ATCC 29213. This EO was found to have high efficacy against biofilm formation, decreasing-by negative regulation-the expression of genes involved in motility (fimH), adherence and cellular aggregation (csgD), and exopolysaccharide production (pgaC) in E. coli. In addition, this effect was also determined in S. aureus where the L. origanoides EO diminished the expression of genes involved in QS communication (agrA), production of exopolysaccharides by PIA/PNG (icaA), synthesis of alpha hemolysin (hla), transcriptional regulators of the production of extracellular toxins (RNA III), QS and biofilm formation transcriptional regulators (sarA) and global regulators of biofilm formation (rbf and aur). Positive regulation was observed on the expression of genes encoding inhibitors of biofilm formation (e.g., sdiA and ariR). These findings suggest that LOTCII EO can affect biological pathways associated with QS communication, biofilm formation, and virulence of E. coli and S. aureus at subinhibitory concentrations and could be a promising candidate as a natural antibacterial alternative to conventional antibiotics.

"BACTERIAL DIVERSITY OF THE GORGONIAN CORAL Plexaura sp.: SCREENING FOR ANTI-PATHOGENIC PROPERTY AGAINST NOSOCOMIAL PATHOGENIC Acinetobacter baumannii "

"Chronic infectious diseases caused by biofilm-forming pathogenic bacteria are the second rank causes of death in Indonesia after heart and blood vessel diseases. The emergence of antibiotic-resistant Acinetobacter baumannii pathogenic bacteria worldwide poses the main medicinal challenge to the search for new antibiotics. However, the use of marine invertebrates as raw material sources is not ecologically friendly due to the low concentration of bioactive compounds in marine invertebrates. This study aimed to investigate gorgonian Plexaura sp.-associated bacteria that have the potential as anti nosocomial pathogenic A. baumannii. A total of 29 gorgonian Plexaura sp.-associated bacterial isolates were screened for their antibacterial activity against nosocomial pathogenic A. baumannii. The 5 bacterial isolates exhibited antipathogenic activity against A. baumannii. The RA17-2 isolate showed the highest diameter size of the inhibition zone. The 16S rRNA sequence analyses revealed that these 5 isolates were closely related to Bacillus, Virgibacillus, and Nitratireductor. None of the 5 antipathogenic isolates possess PKS-I, PKS-II, and NRPS genes, except the PKS-I gene of the RA17-2 isolate. These results showed that Plexauridae sp is a potential source for the development of antibiotic drugs."

Quorum-quenching potential of recombinant PvdQ-engineered bacteria for biofilm formation.

Quorum sensing (QS) is a core mechanism for bacteria to regulate biofilm formation, and therefore, QS inhibition or quorum quenching (QQ) is used as an effective and economically feasible strategy against biofilms. In this study, the PvdQ gene encoding AHL acylase was introduced into Escherichia coli (DE3), and a PvdQ-engineered bacterium with highly efficient QQ activity was obtained and used to inhibit biofilm formation. Gene sequencing and western blot analysis showed that the recombinant pET-PvdQ strain was successfully constructed. The color reaction of Agrobacterium tumefaciens A136 indicated that PvdQ engineering bacteria had shown strong AHL signal molecule quenching activity and significantly inhibited the adhesion (motility) of Pseudomonas aeruginosa and biofilm formation of activated sludge bacteria in Membrane Bio-Reactor (MBR; inhibition rate 51-85%, p < 0.05). In addition, qRT-PCR testing revealed that recombinant PvdQ acylase significantly reduced the transcription level of QS biofilm formation-related genes (cdrA, pqsA, and lasR; p < 0.05). In this study, QQ genetically engineered bacteria enhanced by genetic engineering could effectively inhibit the QS signal transduction mechanism and have the potential to control biofilm formation of pathogenic bacteria in the aquaculture environment, providing an environmentally friendly and alternative antibiotic strategy to suppress biofilm contamination.

Ulcerative colitis alleviation of colon-specific delivered rhamnolipid/fullerene nanocomposites via dual modulation in oxidative stress and intestinal microbiome.

As a typical inflammatory bowel disease (IBD), ulcerative colitis (UC) has become prevalent worldwide in recent years. Though several materials have been proved to be effective in reducing intestinal oxidative stress to alleviate UC symptoms, dependence on high doses of exogenous drugs amplifies their safety risk for patients. To address this challenge, an oral therapy based on colon-targeting delivery of low-dose rhamnolipid (RL)/fullerene (C60) nanocomposites has been reported. With high biocompatibility being verified, RL/C60 largely mitigated the inflammation of mice with colitis shortly after its oral administration. Not only this, but also the intestinal microbiome of diseased mice was remarkably restored to the near-healthy level by our composites. Specifically, RL/C60 significantly promoted the colonization of intestinal probiotics and suppressed the biofilm formation of pathogenic bacteria, which is beneficial for reshaping the intestinal barrier. A close relationship of cytokines and oxidoreductases levels with gut flora further revealed that a change in RL/C60-induced intestinal microecology effectively improved the organismal immune system, which can be considered important for long-time recovery from UC.

Biofilm formation of pathogenic bacteria isolated from aquatic animals

Bacterial biofilm formation is one of the dynamic processes, which facilitates bacteria cells to attach to a surface and accumulate as a colony. With the help of biofilm formation, pathogenic bacteria can survive by adapting to their external environment. These bacterial colonies have several resistance properties with a higher survival rate in the environment. Especially, pathogenic bacteria can grow as biofilms and can be protected from antimicrobial compounds and other substances. In aquaculture, biofilm formation by pathogenic bacteria has emerged with an increased infection rate in aquatic animals. Studies show that Vibrio anguillarum, V. parahaemolyticus, V. alginolyticus, V. harveyi, V. campbellii, V. fischeri, Aeromonas hydrophila, A. salmonicida, Yersinia ruckeri, Flavobacterium columnare, F. psychrophilum, Piscirickettsia salmonis, Edwardsiella tarda, E. ictaluri, E. piscicida, Streptococcus parauberis, and S. iniae can survive in the environment by transforming their planktonic form to biofilm form. Therefore, the present review was intended to highlight the principles behind biofilm formation, major biofilm-forming pathogenic bacteria found in aquaculture systems, gene expression of those bacterial biofilms and possible controlling methods. In addition, the possibility of these pathogenic bacteria can be a serious threat to aquaculture systems.

The Wsp chemosensory system modulates c-di-GMP-dependent biofilm formation by integrating DSF quorum sensing through the WspR-RpfG complex in Lysobacter

The ubiquitous Wsp (wrinkly spreader phenotype) chemosensory system and DSF (diffusible signal factor) quorum sensing are two important chemically associated signaling systems that mediate bacterial communications between the host and environment. Although these two systems individually control biofilm formation in pathogenic bacteria via the ubiquitous second messenger c-di-GMP, their crosstalk mechanisms remain elusive. Here we present a scenario from the plant-beneficial and antifungal bacterium Lysobacter enzymogenes OH11, where biofilm formation favors the colonization of this bacterium in fungal hyphae. We found that the Wsp system regulated biofilm formation via WspR-mediated c-di-GMP signaling, whereas DSF system did not depend on the enzymatic activity of RpfG to regulate biofilm formation. We further found that WspR, a diguanylate cyclase (DGC) responsible for c-di-GMP synthesis, could directly bind to one of the DSF signaling components, RpfG, an active phosphodiesterase (PDE) responsible for c-di-GMP degradation. Thus, the WspR-RpfG complex represents a previously undiscovered molecular linker connecting the Wsp and DSF systems. Mechanistically, RpfG could function as an adaptor protein to bind and inhibit the DGC activity of unphosphorylated WspR independent of its PDE activity. Phosphorylation of WspR impaired its binding affinity to RpfG and also blocked the ability of RpfG to act as an adaptor protein, which enabled the Wsp system to regulate biofilm formation in a c-di-GMP-dependent manner by dynamically integrating the DSF system. Our findings demonstrated a previously uncharacterized mechanism of crosstalk between Wsp and DSF systems in plant-beneficial and antifungal bacteria.

Antibacterial, Antibiofilm, and Anti-Quorum Sensing Potential of Novel Synthetic Compounds Against Pathogenic Bacteria Isolated From Chronic Sinusitis Patients.

Quorum sensing (QS) is a major controller of virulence and biofilm formation in pathogenic bacteria. The aim of the research was to screen novel synthetic compounds (18) from 2 series (Pyrazole and Diene dione) for quorum sensing and biofilm inhibitory potential against resistant pathogens isolated from patients with chronic sinusitis. Most of the compounds have documented zone of inhibition against Gram positive strains Staphylococcus aureus, Enterococcus faecalis and moderate activity against Gram negative Klebseilla pneumoniae and Proteus mirabilis in comparison with standard antibiotic. Compounds Q1 and Q7 have given the maximum zone of inhibition 18 and 20 mm with MICs 0.312 mg/mL and .156 mg/mL against S aureus and E faecalis, respectively. Some compounds were equally potent at inhibiting the formation of biofilm which later established by phase contrast microscopy. Regarding quorum sensing inhibition, the tested concentration of synthetic compound UA3 0.313 mg/mL inhibited violacein production without decreasing Chromobacterium pseudoviolaceum count which was significantly lower than determined MIC’s. It was depicted from the results that selected compounds exhibited low level of cytotoxicity toward human red blood cells. Hence, these findings revealed that most novel compounds were effective antibacterial, whereas compound UA3 has shared significant anti-quorum sensing potential against Chromobacterium pseudoviolaceum.

EVALUATION OF ANTI QUOROM SENSING ACTIVITIES USING Emblica officinalis ETHANOLIC LEAF EXTRACTS AGAINST MARINE MICROBES

Biofilm formation in pathogenic bacteria displays a major role in various human infectious diseases posing a major health problem in several countries. Biofilms contain colony of bacteria which are 1,000 folds more resistant to antibiotics and also they develop more insensitivity to innate and acquired immune responses. Quorum sensing (QS) is characterized well due to the interaction of bacterial cells, which is a dependent mechanism and acts its stimulus response related to population density. In the present study we tested the antiquorum sensing activity with leaf extracts of commonly used dietary supplement Emblica Officinalis (Amla) against marine microbes. In our method, we cultured Klebsilla, Proteus, E.coli, Shigella, Salmonella typhi from marine water source for quorum sensing activities and inhibitory effects through antimicrobial activities. Marine bacteria were isolated, identified based on physical and biochemical characterization. In our results we investigated the inhibitory effects of amla against pathogenic bacteria using swarming method. Further highest inhibitory bacterial isolates were examined under scanning electron microscopy (SEM). We conclude that amla exhibits potential inhibitory effects in biofilms formation from samples obtained from marine waters and further studies are needed in QS gene expression in more number of marine microbial samples.

Inhibitory effects of a water-soluble jujube polysaccharide against biofilm-forming oral pathogenic bacteria

Oral diseases caused by infectious pathogens raises significant concerns in public health. In the light of side effects of current antibiotics therapy and growing drug resistance of pathogenic bacteria, natural products have become attractive alternatives for antibiotics agents in dental practice. This current study investigated the effects of polysaccharides extracted from Zizyphus jujuba Mill. on three major oral biofilm-forming pathogenic bacteria including caries-inducing Streptococcus mutans, lesions-causing MRSA, and periodontitis-related Porphyromonas gingivalis, as well as general oral microbiota. Our results demonstrated that jujube polysaccharide prepared in this study was mainly composed by galacturonic acid with an average molecular weight 242 kDa, which were further characterized for structural features by FT-IR spectra and NMR spectroscopy analysis. This jujube polysaccharide was shown to exhibit remarkable inhibitory effects against all the tested oral bacterial pathogens through various mechanisms including growth inhibition, biofilm prevention and disruption, intervention of bacterial infection (adhesion and invasion), attenuation of cytotoxicity, modulation of excessive inflammatory response of LPS-stimulated and MRSA-infected macrophages as well as positive regulation of oral microbiota. The present study paves the way to explore jujube polysaccharides for the prevention and treatment of oral infectious diseases.Graphic Abstract.

Antibacterial activity of supernatants of Lactoccocus lactis, Lactobacillus rhamnosus, Pediococcus pentosaceus and curcumin against Aeromonas hydrophila. In vitro study.

Secretions of beneficial intestinal bacteria can inhibit the growth and biofilm formation of a wide range of microorganisms. Curcumin has shown broad spectrum antioxidant, anti-inflammatory, and antimicrobial potential. It is important to evaluate the influence of these secretions with bioactive peptides, in combination with curcumin, to limit growth and inhibit biofilm formation of pathogenic bacteria of importance in aquaculture. In the present study, the supernatants of Lactoccocus lactis NZ9000, Lactobacillus rhamnosus GG and Pediococcus pentosaceus NCDO 990, and curcumin (0,1,10,25 and 50μM) were used to evaluate their efficacy in growth, inhibition biofilm and membrane permeability of Aeromonas hydrophila CAIM 347 (A. hydrophila). The supernatants of probiotics and curcumin 1,10 and 25μM exerted similar effects in reducing the growth of A. hydrophila at 12h of interaction. The supernatants of the probiotics and curcumin 25 and 50μM exerted similar effects in reducing the biofilm of A. hydrophila. There is a significant increase in the membrane permeability of A. hydrophila in interaction with 50μM curcumin at two hours of incubation and with the supernatants separately in the same period. Different modes of action of curcumin and bacteriocins separately were demonstrated as effective substitutes for antibiotics in containing A. hydrophila and avoiding the application of antibiotics. The techniques implemented in this study provide evidence that there is no synergy between treatments at the selected concentrations and times.

Antibiofilm activity and bioactive phenolic compounds of ethanol extract from the Hericium erinaceus basidiome.

Biofilm formation has become a serious health and environmental problem. Mushrooms are now considered a valuable source of bioactive compounds with antimicrobial properties. The lion's mane mushroom (Hericium erinaceus [HE]) has been used as an antimicrobial for ulcers and gastritis in East Asian countries. However, studies on the antibiofilm activities of HE basidiome against biofilm-forming pathogenic bacteria and their bioactive compound profiles are still limited. The purpose of this study was to determine the antibiofilm activity of HE and to identify its phenolic compound profile. The HE inhibitory activities against bacterial growth and biofilm formation were performed against Pseudomonas aeruginosa, Salmonella Typhimurium, Proteus mirabilis, and Staphylococcus aureus. Remarkably, P. mirabilis was the most susceptible bacteria to HE. The total phenolic content (TPC) of HE was 1652 ± 1.06 µg/ml, with protocatechuic acid and p-coumaric acid being the most abundant phenolic compounds as determined by high-performance liquid chromatography-mass spectrophotometry (HPLC-MS). This research highlights the possibility of HE as an antibiofilm agent that can be developed as a nutraceutical and natural food preservative.

Evaluation of Quorum-Sensing, Antibiotics Resistance, and Biofilm Formation in Pathogenic Bacteria from the Hospital Environments

Evaluation of Quorum-Sensing, Antibiotics Resistance, and Biofilm Formation in Pathogenic Bacteria from the Hospital Environments

Antibiofilm and Anti-Quorum Sensing Activities of Vaginal Origin Probiotics

Objective: Multidrug-resistant bacteria generally use cell-to-cell communication that leads to biofilm formation as a resistance development mechanism. Some pathogenic bacteria can form biofilms through a mechanism called Quorum sensing (QS). QS inhibition is one of the effective approaches to prevent biofilm formation. Materials and Methods: 20 Lactic acid bacteria (LAB) previously associated with identification by 16S rRNA sequence analysis were used. Antibiofilm activities of metabolites of strains related to microplate based Antibiofilm method on Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853. Chromobacterium violaceum ATCC 12472 was used as an indicator in the anti-QS activities of LAB. The study was also performed by ELISA test on the immunomodulatory effect of LAB human peripheral blood mononuclear cells. Results: All of the metabolites tested showed statistically significant antibiofilm activity on biofilms of pathogenic microorganisms. Although there was a difference between metabolites, Lactobacullus paracasei L2 and L20 strains had a high inhibitory effect on S. aureus (95.1%) and P. aeruginosa by 92.7%, respectively. L. plantarum L8 strain had 95.7% antibiofilm activity on E. coli. It was also determined that LAB has anti-QS activities in different concentrations. The immunomodulatory effect of LAB was found to produce higher IFN‐ γ than the controls, whereas IL-10 concentrations were lower. Conclusion: Bacteria use QS to regulate various sequences of functions, including virulence and biofilm formation. Therefore, using bacteria with strong probiotic properties as QS inhibitory agents seems to be a promising approach to reduce or suppress biofilm formation of pathogenic bacteria.

In Vitro Effect of Copper (I) Complex [Cu(NN1)2](ClO4) on Vibrio harveyi BB170 Biofilm Formation.

Biofilm formation in pathogenic bacteria is an important factor of resistance to antimicrobial treatments, allowing them to survive for a long time in their hosts. In the search for new antibiofilm agents, in this work we report the activity of a copper (I) complex, [Cu(NN1)2]ClO4, synthesized with Cu (I) and NN1, an imine ligand 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one, a derivate of natural compound coumarin. The antibacterial and antibiofilm capacity was evaluated in Vibrio harveyi BB170 used as model bacteria. Antibacterial activity was measured in vitro by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and half-maximal inhibitory concentration (IC50) determination. Antibiofilm capacity of copper (I) complex was analyzed by different concentrations of IC50 values. The results showed that the sub-IC50 concentration, 12.6 µg/mL of the copper (I) complex, was able to reduce biofilm formation by more than 75%, and bacterial viability was reduced by 50%. Inverted and confocal laser scanning microscopy showed that the [Cu(NN1)2]ClO4 complex affected the biofilm structure. Therefore, the copper (I) complex is effective as an antibiofilm compound in V. harveyi BB170.