Microbicidal effects of weakly acidified chlorous acid water against feline calicivirus and Clostridium difficile spores under protein-rich conditions

Abstract

Sanitation of environmental surfaces with chlorine based-disinfectants is a principal measure to control outbreaks of norovirus or Clostridium difficile. The microbicidal activity of chlorine-based disinfectants depends on the free available chlorine (FAC), but their oxidative potential is rapidly eliminated by organic matter. In this study, the microbicidal activities of weakly acidified chlorous acid water (WACAW) and sodium hypochlorite solution (NaClO) against feline calcivirus (FCV) and C. difficile spores were compared in protein-rich conditions. WACAW inactivated FCV and C. difficile spores better than NaClO under all experimental conditions used in this study. WACAW above 100 ppm FAC decreased FCV >4 log10 within 30 sec in the presence of 0.5% each of bovine serum albumin (BSA), polypeptone or meat extract. Even in the presence of 5% BSA, WACAW at 600 ppm FAC reduced FCV >4 log10 within 30 sec. Polypeptone inhibited the virucidal activity of WACAW against FCV more so than BSA or meat extract. WACAW at 200 ppm FAC decreased C. difficile spores >3 log10 within 1 min in the presence of 0.5% polypeptone. The microbicidal activity of NaClO was extensively diminished in the presence of organic matter. WACAW recovered its FAC to the initial level after partial neutralization by sodium thiosulfate, while no restoration of the FAC was observed in NaClO. These results indicate that WACAW is relatively stable under organic matter-rich conditions and therefore may be useful for treating environmental surfaces contaminated by human excretions.

Microbicidal effects of slightly acidic hypochlorous acid water and weakly acidified chlorous acid water on foulbrood pathogens

“…As the bactericidal effects of chlorine-based disinfectants usually increase with a higher ACC, the high disinfecting capacity of WACAW may have simply been due to the high ACC. In addition, the stable microbicidal activity of WACAW under organic matter-rich conditions may have resulted from the large dissociation of total chlorine level and free available chlorine (FAC) level in the disinfectant [12]. WACAW mainly contains HClO 2 , ClO 2 − and ClO 2 as oxygenated chlorines.…”

“…ClO 2 − has very weak oxidative potential and makes only a minor contribution to the FAC level and antimicrobial killing. In WACAW, the ClO 2 − content is considered to be much higher than that of HClO 2 and ClO 2 [12]. This ClO 2 − may continuously supply HClO 2 even after FAC is consumed from contact with microorganisms or organic matter [12].…”

“…In WACAW, the ClO 2 − content is considered to be much higher than that of HClO 2 and ClO 2 [12]. This ClO 2 − may continuously supply HClO 2 even after FAC is consumed from contact with microorganisms or organic matter [12]. Although WACAW has not been used in apiculture, it was approved as a food additive in 2013 in Japan and has since been applied to food and environmental sanitation [12,17].…”

“…Under weakly acidified conditions (pH 5.0-6.0), HClO 2 plays a major role in microbial killing as a predominant species. In previous studies, WACAW was reported to inactivate a wide variety of microorganisms, including endospores of Clostridium, Bacillus and Paenibacillus species [12,17]. In addition, WACAW is relatively stable under organic matter-rich conditions and retains its microbicidal activity [12,17].…”

“…In previous studies, WACAW was reported to inactivate a wide variety of microorganisms, including endospores of Clostridium, Bacillus and Paenibacillus species [12,17]. In addition, WACAW is relatively stable under organic matter-rich conditions and retains its microbicidal activity [12,17]. Therefore, WACAW may also be used as an effective alternative for reducing pathogen contamination of beekeeping equipment.…”