Chlorous acid is a more potent antibacterial agent than sodium hypochlorite against Campylobacter. (May 2020) - Hatanaka, Noritoshi
Abstract: Foodborne disease caused by campylobacters is one of the major global problems for food safety. Infection source of Campylobacter to human is mainly through contaminated meat particularly chicken. Contamination of meat with Campylobacter usually occurs during processing at slaughterhouse and to prevent such contaminations, sodium hypochlorite is commonly used. However, it is well known that bactericidal activity of sodium hypochlorite becomes weak under organic matter rich conditions. In this study, we compared the strength of bactericidal activity of chlorous acid and sodium hypochlorite against Campylobacter jejuni and Campylobacter coli strains under organic matter rich conditions. Bactericidal activity against 5 representative C. jejuni and C. coli strains in chicken juice (an organic matter rich condition) showed that minimum concentration of chlorous acid required for complete killing of C. jejuni and C. coli cells is 200–400 ppm while that of sodium hypochlorite is 2, 000 to 4, 000 ppm. Similar results were obtained by using Bolton broth. Furthermore, it was observed that 400 ppm of chlorous acid but not 400 ppm of sodium hypochlorite is highly effective in killing of 25 different Campylobacter strains (12 C. jejuni and 13 C. coli strains) under the same conditions. To determine whether 400 ppm of chlorous acid treatment had killed bacterial cells or induced them into viable but non-culturable (VBNC) state, live and dead cell assay using DAPI and propidium iodide fluorescent dyes was done. Such assay clearly indicated that Campylobacter cells were indeed killed and not induced to VBNC state. Moreover, SDS-PAGE analysis of whole-cell lysates of campylobacters indicated distinct effects in protein profiles of chlorous acid but not sodium hypochlorite treated cells. The results strongly suggest that chlorous acid could efficiently kill C. jejuni and C. coli cells with much lower concentration than sodium hypochlorite and the bactericidal mechanisms of chlorous acid may be due to damages of bacterial proteins. Thus, chlorous acid could be a better disinfectant in chicken slaughtering and processing to kill campylobacters and prevent contamination. Highlights: Chrolous acid possess stronger bactericidal activity than sodium hypochlorite. Chrolous acid showed bactericidal activity even under high protein concentration. Chrolous acid killed Campylobacter by affecting their proteins rather DNA. Chrolous acid might be useful disinfectant in chicken processing steps.