Antibiotic resistant pattern and biofilm formation ability of chlorine adapted Salmonella enterica cells

Background and Aim : Adaptation phenomenon could takes place over time and with increasing contact of microorganisms to progressive concentrations of stresses such as disinfectants. Any exposure of bacteria to sub-lethal concentrations of disinfectants may be constitute a critical public health such as emergence of higher invasive pathogens with reduced susceptibility to antibiotics and ability to form biofilm.Methods : In this study, we obtained minimum inhibitory concentration (MIC) of Salmonella enterica against sodium hypochlorite disinfectant containing ۵۰۰۰۰ ppm chlorine, then bacterium was adapted to progressive concentrations of chlorine (from ۱۲۵ ppm to ۳۰۰۰ ppm with ۲۵ ppm daily increase of chlorine concentration) to the extent that could tolerate MIC. Antibiotic resistance (against ampicillin, amikacin, trimethoprim, ceftriaxone, and nalidixic acid) and biofilm formation ability was determined before and after chlorine adaptation. Biofilm formation ability was done in sterile ۹۶ well microtiter plates using TSB media and by optical density measuring at ۶۰۰ nm using an Elisa reader. Results : Antibiotic susceptibility findings on Mueller-Hinton agar revealed highest and significance (p<۰.۰۵) resistance to ceftriaxone after stress adaptation, so that sensitivity from ۳۰ mm inhibition zone before adaptation reached to ۰ mm after chlorine adaptation. Findings showed moderate ability of salmonella enterica before adaptation that remained stable after chlorine adaptation. Conclusion : Finally, we could conclude chlorine disinfectants with regular use in food industry have potential for the development of bacterial adaptation and in this way induction of antibiotic resistance and increase in biofilm formation ability must be taken into account.

کلیدواژه ها:

Salmonella enterica ، Chlorine adaptation ، Antibiotic resistant pattern ، Biofilm formation