Subject(s)
Anti-Bacterial Agents/pharmacology , Biofilms/drug effects , Gram-Positive Bacteria/drug effects , Pyrroles/pharmacology , Staphylococcus/drug effects , Anti-Bacterial Agents/chemical synthesis , Microbial Sensitivity Tests , Pyrroles/chemical synthesis , Pyrroles/chemistry , Structure-Activity Relationship , Vancomycin/pharmacologyABSTRACT
AIMS: To investigate the effect of oxygen limitation, glucose-starvation and temperature on the susceptibility of Escherichia coli towards the quaternary ammonium biocide benzalkonium chloride (BAC). METHODS AND RESULTS: The effect of BAC on planktonic and sessile cells were investigated using the gfp-tagged E. coli K-12 strain MG1655[pOX38Km]. Increasing temperature from 10 degrees C to 30 degrees C increased the bactericidal effect of BAC for both starved and nonstarved E. coli under aerobic and anaerobic conditions. The lowest minimum bactericidal concentration was observed for cells in anaerobic media at 30 degrees C (30 mg l(-1) BAC). Decreasing cell densities increased the decay rate for BAC-exposed cells for both starved and nonstarved E. coli. Biofilms of E. coli exposed to BAC in anaerobic medium showed a greater percentage of membrane-compromised cells than biofilms grown in aerobic medium. Image analyses of BAC-exposed biofilms showed that membrane-compromised cells were occasionally located in the interior structure of the biofilm microcolonies. CONCLUSIONS: Increasing temperatures and the absence of oxygen, and energy substrates increased the antimicrobial effect of BAC towards E. coli. SIGNIFICANCE AND IMPACT OF THE STUDY: The results are relevant for understanding the disinfection efficacy of quaternary ammonium compounds towards planktonic and sessile bacteria.
Subject(s)
Anti-Bacterial Agents/pharmacology , Anti-Infective Agents, Local/pharmacology , Benzalkonium Compounds/pharmacology , Biofilms/drug effects , Escherichia coli/drug effects , Glucose/metabolism , Oxygen/pharmacology , Anaerobiosis , Biofilms/growth & development , Carbon Dioxide/metabolism , Drug Resistance, Bacterial , Escherichia coli/growth & development , Escherichia coli/physiology , Microbial Sensitivity Tests , Plankton/drug effects , Plankton/growth & development , TemperatureABSTRACT
A computational model explaining formation of mushroom-like biofilm colonies is proposed in this study. The biofilm model combines for the first time cell growth with twitching motility in a three-dimensional individual-based approach. Model simulations describe the tendency of motile cells to form flat biofilms spreading out on the substratum, in contrast with the immotile variants that form only round colonies. These computational results are in good qualitative agreement with the experimental data obtained from Pseudomonas aeruginosa biofilms grown in flowcells. Simulations reveal that motile cells can possess a serious ecological advantage by becoming less affected by mass transfer limitations. Twitching motility alone appears to be insufficient to generate mushroom-like biofilm structures with caps on stalks. Rather, a substrate limitation-induced detachment of motile cells followed by reattachment could explain this intriguing effect leading to higher-level biofilm structure.
