The Effect of Repeated Sodium Hypochlorite Exposure on Chlorine Resistance Development in Escherichia coli O157:H7

Abstract

Chlorine water has been widely used to reduce viable bacterial contamination on food surfaces and sanitize processing facilities. The emergence and spread of microorganisms with reduced susceptibility to antimicrobial agents is a major public health problem. This in vitro study was designed to evaluate the possibility that E. coli O157:H7 can acquire chlorine resistance and subsequent induction of cross-resistance to chlorine water. In addition, the occurrence of spontaneous chlorine resistance mutations or a higher mutation rate introduced by chemical mutations as compared to the standard was also examined. Comparisons of bacterial viability, cellular activity and susceptibility to antibiotics before and after repeated cycles of enrichment cultivation were performed. There were no significant changes observed in bactericidal sensitivity during repeated cultivation in both NTG treated and non-treated cells (n = 6, P > 0.05). There were no significant differences in the activity of cellular respiration enzymes, oxidative stress related gene expression and susceptibility to antibiotics observed in both the NaClO treated samples (n=8, P<0.01) as compared to the control. These results suggested that it might be difficult for E. coli O157:H7 to acquire resistance to chlorine solution even though the bacteria were exposed to NaClO and continued to proliferate.