Antibiotic Resistance Induction by Benzalkonium Chloride Exposure in Nosocomial Pathogens

Background Biocides (disinfectants) are crucial for controlling various infections and are widely used in environments for the control of microorganisms. Exposure of bacteria to biocides can select for mutants with decreased biocide susceptibility that often display a decrease in susceptibility to antibiotics. Objectives The present work was done during 14 months from February 2015, at the microbiology laboratory of the Veterinary college of Shahrekord university with the aim of investigating the impact of benzalkonium chloride exposure on antibiotic resistance in some common nosocomial pathogens. Methods Standard strains of Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli and Staphylococcus aureus were used, and in parallel to each standard strain four hospital isolates collected from Shahrekord and Esfahan hospitals were examined. Tube double serial dilution method was used for determination of minimum inhibitory concentration (MIC) of antibiotics and Benzalkonium Chloride (BKC). Spontaneous mutants were developed by exposure of examined species to BKC, and their mean MICs to examined drugs were evaluated. Results The mean MICs of the BKC and antibiotics used in this study were not similar between the parent and mutant strains of the examined isolates. In E. coli, A. baumannii and S. aureus isolates, differences between the mean MICs of BZK and ciprofloxacin had a similar pattern and were statistically significant (P < 0.05). In isolates of P. aeruginosa, differences between parent and mutant isolates for all of the tested drugs were significant. Conclusions Vast use of BKC in various environments and their accumulation represents a potential risk for selective pressure towards selection of bacteria with decreased antibiotic susceptibility.