RESUMO
BACKGROUND: Resistance toward quaternary ammonium compounds (QACs) is widespread among a diverse range of microorganisms and is facilitated by several mechanisms such as biofilm formation. OBJECTIVES: In this study, the effects of benzalkonium chloride on planktonic growth and biofilm formation by some field isolates of animal bacterial pathogens were investigated. MATERIALS AND METHODS: Forty clinical isolates of Escherichia coli, Salmonella serotypes, Staphylococcus aureus and Streptococcus agalactiae (10 isolates of each) were examined for effects of benzalkonium chloride on biofilm formation and planktonic growth using microtiter plates. For all the examined strains in the presence of benzalkonium chloride, biofilm development and planktonic growth were affected at the same concentrations of disinfectant. RESULTS: The means of strains growth increase after the minimal inhibitory concentration (MIC) were significant in all the bacteria (except for E. coli in 1/32 and S. agalactiae in of 1/8 MIC). Biofilm formation increased with decrease of antiseptics concentration; a significant increase was found in all the samples. The most turbidity related to S. aureus and the least to Salmonella. CONCLUSIONS: Bacterial resistance against quaternary ammonium compounds is increasing which can increase the bacterial biofilm formation.
RESUMO
BACKGROUND: To study chlorhexidine digluconate disinfectant effects on planktonic growth and biofilm formation in some bacterial field isolates from animals. OBJECTIVES: The current study investigated chlorhexidine digluconate effects on planktonic growth and biofilm formation in some field isolates of veterinary bacterial pathogens. MATERIALS AND METHODS: Forty clinical isolates of Escherichia coli, Salmonella serotypes, Staphylococcus. aureus and Streptococcus agalactiae (10 isolates for each) were examined for chlorhexidine digluconate effects on biofilm formation and planktonic growth using microtiter plates. In all of the examined strains in the presence of chlorhexidine digluconate, biofilm development and planktonic growth were affected at the same concentrations of the disinfectant. RESULTS: Chlorhexidine digluconate inhibited the planktonic growth of different bacterial species at sub-MICs. But they were able to induce biofilm development of the E. coli, Salmonella spp., S. aureus and Str. agalactiae strains. CONCLUSIONS: Bacterial resistance against chlorhexidine is increasing. Sub-MIC doses of chlorhexidine digluconate can stimulate the formation of biofilm strains.
