Growth Of Bacteria In Biofilms Research Articles

Synthesis, in Silico Study and Biological Evaluation of N-(Benzothiazol/Thiazol-2-yl)benzamide Derivatives as Quorum Sensing Inhibitors against Pseudomonas aeruginosa.

The development of bacterial resistance to chemical therapy poses a severe danger to efficacy of treating bacterial infections. One of the key factors for resistance to antimicrobial medications is growth of bacteria in biofilm. Quorum sensing (QS) inhibition was created as an alternative treatment by developing novel anti-biofilm medicines. Cell-cell communication is impeded by QS inhibition, which targets QS signaling pathway. The goal of this work is to develop newer drugs that are effective against Pseudomonas aeruginosa by decreasing QS and acting as anti-biofilm agents. In this investigation, N-(benzo[d]thiazol-2-yl)benzamide/N-(thiazol-2-yl)benzamide derivatives 3a-h were designed and synthesized in good yields. Further, molecular docking analyses revealed that binding affinity values were founded -11.2 to -7.6 kcal/mol that were moderate to good. The physicochemical properties of these prepared compounds were investigated through in-silico method. Molecular dynamic simulation was also used to know better understanding of stability of the protein and ligand complex. Comparing N-(benzo[d]thiazol-2-yl)benzamide 3a to salicylic acid (4.40±0.10) that was utilised as standard for quorum sensing inhibitor, the anti-QS action was found greater for N-(benzo[d]thiazol-2-yl)benzamide 3a (4.67±0.45) than salicylic acid (4.40±0.10). Overall, research results suggested that N-(benzo[d]thiazol-2-yl)benzamide/N-(thiazol-2-yl)benzamide derivatives 3a-h may hold to develop new quorum sensing inhibitors.

Impacts of antibiotics on biofilm bacterial community and disinfection performance on simulated drinking water supply pipe wall

Overuse of antibiotics is accelerating the spread of resistance risk in the environment. In drinking water supply systems, the effect of antibiotics on the resistance of biofilm is unclear, and there have been few studies in disinfectant-containing systems. Here, we designed a series of drinking water supply reactors to investigate the effects of antibiotics on biofilm and bacteria in the water. At low concentrations, antibiotics could promote the growth of bacteria in biofilm; among the tested antibiotics (tetracycline, sulfadiazine and chloramphenicol), tetracycline had the strongest ability to promote this. And the antibiotic resistant bacteria (ARB) could inhibit the growth of bacteria in drinking water. Results have shown that antibiotics enhanced the bacterial chlorine resistance in the effluent, but reduced that in the biofilm. Furthermore, metagenomic analysis showed that antibiotics reduced the richness of biofilm communities. The dominant phyla in the biofilm were Proteobacteria, Planctomycetes, and Firmicutes. In tetracycline-treated biofilm, the dominant phylum was Planctomycetes. In sulfadiazine- and chloramphenicol-treated groups, bacteria with complex cell structures preferentially accumulated. The dominant class in biofilm in the ARB-added group was Gammaproteobacteria. The abundance of antibiotic resistant genes (ARGs) was correlated with biofilm community structure. This study shows that antibiotics make the biofilm community structure of drinking water more resistant to chlorine. ARGs may be selective for certain bacteria in the process, and there may ultimately be enhanced chlorine and antibiotic resistance of effluent bacteria in drinking water.

Polymeric Composites with Silver (I) Cyanoximates Inhibit Biofilm Formation of Gram-Positive and Gram-Negative Bacteria.

Biofilms are surface-associated microbial communities known for their increased resistance to antimicrobials and host factors. This resistance introduces a critical clinical challenge, particularly in cases associated with implants increasing the predisposition for bacterial infections. Preventing such infections requires the development of novel antimicrobials or compounds that enhance bactericidal effect of currently available antibiotics. We have synthesized and characterized twelve novel silver(I) cyanoximates designated as Ag(ACO), Ag(BCO), Ag(CCO), Ag(ECO), Ag(PiCO), Ag(PICO) (yellow and red polymorphs), Ag(BIHCO), Ag(BIMCO), Ag(BOCO), Ag(BTCO), Ag(MCO) and Ag(PiPCO). The compounds exhibit a remarkable resistance to high intensity visible light, UV radiation and heat and have poor solubility in water. All these compounds can be well incorporated into the light-curable acrylate polymeric composites that are currently used as dental fillers or adhesives of indwelling medical devices. A range of dry weight % from 0.5 to 5.0 of the compounds was tested in this study. To study the potential of these compounds in preventing planktonic and biofilm growth of bacteria, we selected two human pathogens (Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus) and Gram-positive environmental isolate Bacillus aryabhattai. Both planktonic and biofilm growth was abolished completely in the presence of 0.5% to 5% of the compounds. The most efficient inhibition was shown by Ag(PiCO), Ag(BIHCO) and Ag(BTCO). The inhibition of biofilm growth by Ag(PiCO)-yellow was confirmed by scanning electron microscopy (SEM). Application of Ag(BTCO) and Ag(PiCO)-red in combination with tobramycin, the antibiotic commonly used to treat P. aeruginosa infections, showed a significant synergistic effect. Finally, the inhibitory effect lasted for at least 120 h in P. aeruginosa and 36 h in S. aureus and B. aryabhattai. Overall, several silver(I) cyanoximates complexes efficiently prevent biofilm development of both Gram-negative and Gram-positive bacteria and present a particularly significant potential for applications against P. aeruginosa infections.

Phosphorylcholine-Based Polymer Encapsulated Chitosan Nanoparticles Enhance the Penetration of Antimicrobials in a Staphylococcal Biofilm.

Biofilms that contribute to the persistent bacterial infections pose serious threats to human health, due in part to the extracellular polymeric substances (EPS) matrix of biofilm block the diffusion of intact antimicrobials. The poor penetration of antimicrobials into biofilm greatly reduces their bacterial killing efficacy. Here, we have demonstrated a nanocapsule PMPC-CS synthesized by encapsulating a chitosan nanoparticle with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Such PMPC-based surface exhibited low EPS-adsorption, allowing enhanced penetration of PMPC-CS. Additionally, PMPC-CS showed effective targeting toward negatively charged bacterial cell surfaces and pH-responsive drug release mediated by the swelling of chitosan core under the acidic environment of biofilm. These unique features ensured targeted delivery of antimicrobials throughout the depth of a biofilm. Delivery of triclosan with PMPC-CS outperformed direct application of free triclosan in inhibiting the growth of bacteria in biofilm, suggesting the potential of PMPC-CS as an effective delivery system for the treatment of bacterial infections.

Preparation and Antibiofilm Properties of Zinc Oxide/Porous Anodic Alumina Composite Films

The PAA (porous anodic alumina) films were prepared by two-step anodic oxidation after different times, and then the ZnO/PAA composite films were prepared by sol-gel method on their surface. Meanwhile, the ZnO/PAA composite films were characterized by X-ray diffraction (XRD), thermogravimetric/differential thermal analyzer (TG/DTA), Fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and water contact angle (CA). The antibiofilm properties of ZnO/PAA composite films on Shewanella putrefaciens were measured simultaneously. The results show that the micromorphologies of PAA and ZnO/PAA composite films are affected by second anodization time. ZnO is a hexagonal wurtzite structure, and ZnO particles with a diameter of 10–30 nm attach to the inner or outer surfaces of PAA. After being modified by Si69, the ZnO films translate from hydrophilia to hydrophobicity. The ZnO/PAA film with the optimal antibiofilm properties is prepared on the PAA surface by two-step anodization for 40 min. The adherence of Shewanella putrefaciens is restrained by its super-hydrophobicity, and the growth of biofilm bacteria is inhibited by its abundant ZnO particles.

English

Two species of common seaweeds and a single species of sponge were collected from Tuticorin coast and screened for antifouling activity. The seaweeds, Sargassum wightii, Ulva lactuca; sponge Desmopsongiae sp., and cashew nut oil extracts were tested in vitro against ten marine fouling bacteria isolated from test panels and the green mussel Perna viridis. The biofilm bacteria growth was inhibited by methanol extracts of the seaweeds S. wightii, U. lactuca, sponge Desmospongae sp., and the tropical cashew nut oil extracts. The bacterial growth was strongly inhibited by using extract concentrations as low as 30 µg mL−1 with S. wightii, U. lactuca, Desmospongiae sp., and cashew nut oil. The byssus thread formation of the mussel was completely inhibited by methanol extracts of S. wightii, U. lactuca and cashew nut oil extracts at concentrations of 100 µg ml-1. These extracts showed strong antifouling activities on green mussel attachment with 100 µg ml-1 concentration. In this present study, there are exhibited preliminary evaluation of novel antifouling agents from marine macroalgae and tropical cashew nut oil.   Key words: Perna viridis, marine fouling bacteria, macroalgae, antifouling and tropical.

Photodynamic therapy: Truly a marriage between a drug and a light

Microbial biofilms in the oral cavity are involved in the etiology of various oral conditions, including caries, periodontal and endodontic diseases, oral malodor, denture stomatitis, candidiasis and dental implant failures. It is generally recognized that the growth of bacteria in biofilms imparts a substantial decrease in susceptibility to antimicrobial agents compared with cultures grown in suspension. It is therefore not surprising that bacteria growing in dental plaque, a naturally occurring biofilm, show increased resistance to antimicrobial agents. As result there is pronounced interest and keenness in the development of alternate antimicrobial concepts. Therefore, the application of alternative method to eradicate bacteria from periodontal pockets is desirable. One such approach is photodynamic therapy (PDT). The purpose of this review was to evaluate the effectiveness of PDT for periodontitis as an adjunct to non-surgical treatment of scaling and root planning. This review provides an overview of PDT with emphasis on its current status as an antimicrobial therapy to control oral bacteria. Finally, new frontiers of antimicrobial PDT research will be introduced, including targeting strategies that may open new opportunities for the maintenance of bacterial homeostasis in dental plaque, thereby providing the opportunity for more effective disease prevention and control. Thus, the available knowledge of PDT should encourage a more clinically oriented application of this technique.

Biofilm-forming Pseudomonas aeruginosa bacteria undergo lipopolysaccharide structural modifications and induce enhanced inflammatory cytokine response in human monocytes

To determine whether growth of bacteria in biofilms triggers a specific immune response, we compared cytokine induction in human monocytes and mouse macrophages by planktonic and biofilm bacteria. We compared Pseudomonas aeruginosa and Staphylococcus aureus, two bacteria often colonizing the airways of cystic fibrosis patients. Planktonic and biofilm S. aureus induced equivalent amounts of cytokine in human monocytes. In contrast, biofilm-forming P. aeruginosa induced a higher production of tumor necrosis factor and interleukin-6 than their planktonic counterpart, both for clinical isolates and laboratory strains. This increased cytokine production was partly dependent on phagocytosis. In contrast, no difference in cytokine induction was observed with mouse macrophages. We investigated the structures of the lipopolysaccharides (LPSs) of these Gram-negative bacteria in biofilm and planktonic cultures of P. aeruginosa. Switch between the two life-styles was shown to cause several reversible LPS structure modifications affecting the lipid A and polysaccharide moieties of both clinical isolates and laboratory strains. In addition, LPS isolated from biofilm-grown bacteria induced slightly more inflammatory cytokines than that extracted from its planktonic counterpart. Our results, therefore, show that P. aeruginosa biofilm LPS undergoes structural modifications that only partially contribute to an increased inflammatory response from human monocytes.

Interaction of Colloidal Fe/Mn Oxides Concentration and Shear Stress on Biofilm Formation

Six test runs were carried out to explore the interaction of shear stress and Fe/Mn oxides concentration on the growth of heterotrophic micro-organisms in biofilms. Experimental results revealed that the existence of Fe/Mn colloids was beneficial to biofilm formation. Significant interactions existed (p < 0.001) between shear stress and influent Fe/Mn concentration on biofilm bacteria growth and dissolved organic carbon consumption. Biofilm bacteria numbers were positively related to the dissolved organic carbon consumption rate. This implies that the influent Fe/Mn concentration did not interfere with the uptake of the carbon source by biofilm bacteria. At a higher Fe/Mn concentration (HCS), the biofilm HPC number significantly increased with an increase in shear stress. However, the opposite relation was found at a lower Fe/Mn concentration (LCS). A significant interaction existed between influent colloidal Fe/Mn concentration and shear stress on the kinetic and yield parameters specific growth rate (μb), specific substrate utilization rate (q), and observed growth yield (γobs). The size distribution of particles based on particle concentration (No · ml−1) was also examined in the study.

Comparative Assessment of the Antimicrobial Susceptibility ofStaphylococcus aureusIsolates from Bovine Mastitis in Biofilm Versus Planktonic Culture

Mastitis is one of the most important diseases in dairy cattle of which Staphylococcus aureus is a major pathogen. Despite an apparently good antimicrobial susceptibility in vitro, the cure of diseased animals from this bacteriological infection is often disappointing, which results in cases of recurrent clinical- and chronic subclinical infections. It has been suggested that these recurrent and chronic Staphylococcus infections can be attributed to the growth of bacteria in biofilm. The objective of this study was to compare the susceptibility for antimicrobial agents of S. aureus isolates obtained from bovine mastitis growing under different conditions. These conditions include a conventional conventional microbroth dilution assay in which minimal inhibitory concentration values are determined, the MBEC assay which measures both the susceptibility in biofilm and the susceptibility of sequester cells released from the biofilm. A comparison of the susceptibility for antimicrobial agents of a number of representative S. aureus isolates grown in broth (representing in vitro growth conditions) or milk (representing in vivo growth conditions) is also made. The results indicate that S. aureus isolates obtained from bovine mastitis are highly resistant to antimicrobial agents when growing in biofilms.

Modelling biofilm growth and disinfectant decay in drinking water

A simple biofilm model was developed to describe the growth of bacteria in drinking water biofilms and the subsequent interactions with disinfectant residuals incorporating the important processes, such as attachment of free bacteria to the biofilm on a wall surface, detachment of bacteria from the biofilm, growth of biofilm bacteria with chloramine inhibition, chloramine decay in the bulk water phase, and chloramine decay due to biofilm bacteria and wall surfaces. The model is useful in evaluating the biological stability of different waters, as it can predict concentration of organic substances in water. In addition, the model can be used to predict the bacterial growth and biofilm decay in distribution systems. A model of this kind is a useful tool in developing system management strategies to ultimately improve drinking water quality.

Formation and bacterial composition of young, natural biofilms obtained from public bank-filtered drinking water systems

In Germany, bank-filtered raw water and ground water is mainly used for drinking water conditioning. Microorganisms, which are neither retarded by the subsoil passage of the bank-filtration, nor by the different filtration and disinfection steps at the water works, cause the growth of biofilms on different materials originally used in drinking water distribution systems. The development, the phylogenetical diversity and the bacterial metabolic activities of biofilms on polyethylen (PE-HD), polyvinylchlorid (PVC), steel and copper were analyzed at different sampling points. The incubation experiments were performed under natural conditions using a flow device technique. The devices were installed after the activated carbon filters and disinfection step at the water works and at two different house branch connections within the distribution system of the conditioned drinking water of the water works. The synthetic materials were colonized very rapidly within a few days in significant higher densities than steel and copper. The total bacterial cell counts of the biofilms were measured by DAPI (4′,6-diamidino-2-phenylindole) staining. The metabolic activities of the bacteria were quantified by the use of the redox dye CTC (5-cyano-2,3-ditolyl tetrazolium chloride), which is frequently described as an indicator for respiration. The highest respiratory activities were observed in biofilms from synthetic materials grown after the activated carbon filters at the water works. A significant reduction of the total bacterial cell counts and respiratory activities of about 80% was measured due to the disinfection at the water works. A time dependent growth of bacteria in biofilms was observed at the two sampling points within the distribution system, whereas the percentage of CTC-reducing cells stabilized at 35%. The in situ-hybridizations with fluorescence labelled, group-specific rRNA targeted oligonucleotide probes revealed the following: (i) bacteria of the Beta- and Gamma-subclass of Proteobacteria were found most frequently within the biofilm population, (ii) the percentage of the different subclasses depended on the used material, (iii) there were no significant changes in bacterial subclass composition of the biofilms taken from the water works and house branch connections. In addition, polymerase chain reaction (PCR), southern blot hybridization and in situ hybridization were used to detect facultative pathogenic bacteria in biofilms. Non-pneumophila Legionella were found in a relative high percentage up to about 7% in many biofilms, whereas fecal streptococci were detected only in few biofilms of the drinking water distribution systems

Toluene degradation kinetics for planktonic and biofilm-grown cells ofPseudomonas putida 54G

Toluene degradation kinetics by biofilm and planktonic cells of Pseudomonas putida 54G were compared in this study. Batch degradation of (14)C toluene was used to evaluate kinetic parameters for planktonic cells. The kinetic parameters determined for toluene degradation were: specific growth rate, micro(max) = 10.08 +/- 1.2/day; half-saturation constant, K(S) = 3.98 +/- 1.28 mg/L; substrate inhibition constant, K(I) = 42.78 +/- 3.87 mg/L. Biofilm cells, grown on ceramic rings in vapor phase bioreactors, were removed and suspended in batch cultures to calculate (14)C toluene degradation rates. Specific activities measured for planktonic and biofilm cells were similar based on toluene degrading cells and total biomass. Long-term toluene exposure reduced specific activities that were based on total biomass for both biofilm and planktonic cells. These results suggest that long-term toluene exposure caused a large portion of the biomass to become inactive, even though the biofilm was not substrate limited. Conversely, specific activities based on numbers of toluene-culturable cells were comparable for both biofilm and planktonically grown cultures. Planktonic cell kinetics are often used in bioreactor models to model substrate degradation and growth of bacteria in biofilms, a procedure we found to be appropriate for this organism. For superior bioreactor design, however, changes in cellular activity that occur during biofilm development should be investigated under conditions relevant to reactor operation before predictive models for bioreactor systems are developed.

Toluene degradation kinetics for planktonic and biofilm‐grown cells of Pseudomonas putida 54G

Toluene degradation kinetics by biofilm and planktonic cells of Pseudomonas putida 54G were compared in this study. Batch degradation of 14C toluene was used to evaluate kinetic parameters for planktonic cells. The kinetic parameters determined for toluene degradation were: specific growth rate, μmax = 10.08 ± 1.2/day; half-saturation constant, KS = 3.98 ± 1.28 mg/L; substrate inhibition constant, KI = 42.78 ± 3.87 mg/L. Biofilm cells, grown on ceramic rings in vapor phase bioreactors, were removed and suspended in batch cultures to calculate 14C toluene degradation rates. Specific activities measured for planktonic and biofilm cells were similar based on toluene degrading cells and total biomass. Long-term toluene exposure reduced specific activities that were based on total biomass for both biofilm and planktonic cells. These results suggest that long-term toluene exposure caused a large portion of the biomass to become inactive, even though the biofilm was not substrate limited. Conversely, specific activities based on numbers of toluene-culturable cells were comparable for both biofilm and planktonically grown cultures. Planktonic cell kinetics are often used in bioreactor models to model substrate degradation and growth of bacteria in biofilms, a procedure we found to be appropriate for this organism. For superior bioreactor design, however, changes in cellular activity that occur during biofilm development should be investigated under conditions relevant to reactor operation before predictive models for bioreactor systems are developed. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 535–546, 1997.

Catheter-associated urinary tract infections: Epidemiology, pathogenesis, and prevention

Catheter-associated urinary tract infections (UTI c) remain the most common nosocomial infection. Although usually benign, UTI c cause bacteremia in 2–4% of patients and have been associated with a case fatality rate three times as high as nonbacteriuric patients. Risk factors for UTI c identified in multivariate analyses include increasing duration of use, female sex, absence of systemic antibiotics, and disconnection of the catheter-collecting tube junction. Recent studies suggest that most episodes of low colony count bacteriuria (10 2-10 4 cfu/ml) rapidly progress to high (≥10 5/ml) colony counts within 24–48 hours. In persons with long-term catheterization, bacteriuria inevitably develops and the infecting strains change frequently. In this setting, Proteus and Morganella species produce catheter encrustations and persistent bacteriuria. Routes of bacterial entry have been well defined and differ by gender, with the periurethral route predominating in women and the intraluminal route in men. Growth of bacteria in biofilms on the inner surface of catheters promotes encrustation and may protect bacteria from antimicrobial agents. Bacterial virulence factors have not been well characterized in UTI c, but fimbrial adhesins have been associated with bacterial persistence in the catheterized urinary tract, and urease production has been associated with stone formation and catheter encrustation. Recent efforts to prevent UTI c have focused mainly on preventing bacterial entry to the urinary tract or eradicating bacteriuria after its onset and have been largely unsuccessful. Systemic antimicrobials, sealed tubing and catheter junctions, silver ion-coated catheters, and antiseptics in the collecting bag have all been efficacious in one or more controlled trials. Failure to stratify patients by major risk factors, especially gender, antimicrobial exposure, and catheter duration, makes interpretation of many trials difficult. Further research in the areas of innovative catheter system design, bacterial-host epithelial cell interaction, and targeted antimicrobial prophylaxis seem the most likely approaches to controlling UTI c in the future.