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ISSN : 2287-7991(Print)
ISSN : 2287-8009(Online)
Journal of the Preventive Veterinary Medicine Vol.37 No.1 pp.49-52

Antimicrobial effect of hypochlorous acid on pathogenic microorganisms

Se Chang Park1,†, Sang Phil Shin1,*, Mun Sup Kim1,*, Sung Hee Cho2, Ji Hyung Kim1, Casiano H. Choresca Jr1, Jee Eun Han1, Jin Woo Jun1
1College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Republic of Korea
2R&D Department, Yuhan-Clorox Co. Ltd, Incheon 403-030, Republic of Korea
Received 7 January 2013, revised 20 March 2013, accepted 21 March 2013


Disinfection is essential in terms of the public health or environmental hygiene. Hypochlorous acid (HOCl) solutionwas developed as a disinfectant in Korea. We evaluated the germicidal activity of HOCl against various pathogenic microbes.Thirty-one ATCC strains were exposed to HOCl solution at various concentrations (20, 40 and 80 ppm) for 1 minute. All thestrains of bacteria, yeasts and mycobacteria were killed at 80 ppm after exposure to HOCl. The results suggest that HOClsolution could be used to effectively disinfect public areas.

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Public health has been defined as the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations both public and private, communities and individuals [17]. Environmental health (or environmental hygiene) is a branch of public health concerned with all aspects of the natural and built environment that may affect human health. Other phrases that concern or refer to the discipline of environmental health include environmental public health and environmental health and protection. Disinfectants in terms of public health safety have been used to destroy microorganisms on non-living objects and sanitizers are agents that decrease the level of microorganisms present on the surface of an abiotic material [16]. Hypochlorous acid (HOCl) is a weak acid and dissociates to the hypochlorite ion (-OCl) and proton (H+ ) depending on the solution pH. Both HOCl and -OCl are strong oxidizing agents and show germicidal activity [10]. Previous studies have reported that HOCl is 80 times more effective against Escherichia coli and 40 times more effective to Pseudomnas spp. than -OCl [13, 15]. However , until now, HOCl has simply been thought of as a transient by-product of ubiquitous chlorine disinfectants because of the difficulty to isolate and purify it. We made highly concentrated and stable HOCl with patented technology (patent Number 10-1051312). The purpose of this study, therefore, was to evaluate the disinfectant activity of HOCl against various pathogenic microbes. Our results showedthat HOCl is an effective disinfectant. 

 HOCl solution (3,000 ppm) was diluted with phosphate buffered saline (PBS) to 20, 40 and 80 ppm. The following strains were cultured in Tryptic Soy Broth (TSB) at 37℃ (Bacillus sp. and Paenibacillus alvei at 30℃) for 24 h: 2 Staphylococcus aureus subsp. aureus, 2 Enterococcus faecalis, 2 Escherichia coli, 2 Pseudomonas aeruginosa, 3 Methicillin resistant Staphylococcus aureus (MRSA), 1 Salmonella enterica subsp. enterica (typhimurium), 1 Shigella sonnei, 1 Shigella flexneri , 1 Bacillus thuringiensis, 1 Bacillus cereus, 1 Bacillus cereus, 1 Bacillus circulans and 1 Paenibacillus alvei. Eight Candida albicans were cultured in Yeast extract-Malt extract Broth (YMB) at 37℃ for 24 h. Mycobacterium chelonae subsp. Chelonae, Mycobacterium ortuitum subsp. fortuitum and Mycobacterium smegmatis were cultured in 3% OGAWA media at 37℃ for 24 h. Listonella anguillarum was cultured in 1% TSB at 25℃ for 24 h. All strains were diluted with PBS to over 108  CFU/㎖ and 0.1 ㎖ of the dilution was added to 9.9 ㎖ of HOCl solution. After 1 min, the 0.1 ㎖ mixtures were inoculated on Tryptic soy agar (TSA), Yeast extract-Malt extract Agar (YMA), 3% OGAWA media and 1% NaCl TSA and incubated at the optimal temperatures described above for 24~48 h.

Table 1. Antimicrobial effect of hypochlorous acid according to concentration

 Almost all strains were killed at 40 ppm. Especially Mycobacterium spp. and L. anguillarum were inactivated at 20 ppm while Bacillus spp. and P. alvei were not recovered at 80 ppm. The results of this study are presented in Table 1. Previous studies have reported that HOCl showed a germicidal effect within 0.5~1 min at 80 ~100 ppm [6, 7]. Our result indicates that HOCl has good bactericidal effect on Mycobacterium spp. over 20 ppm and it is similar to previously reported results [14]. In addition, S. aureus subsp. aureus, E. faecalis, E. coli, P. aeruginosa, MRSA, S. typhimurium, S. sonnei, S. flexneri and C. albicans were inactivated at 40 ppm. However, Bacillus sp. and Panibacillus alvei were killed at 80 ppm. Previous studies [6, 7] mainly showed the germicidal effect on pathogenic microbes at 80 ~ 100 ppm HOCl. However, this study demonstrated the germicidal effects of HOCl at lower a concentration with a greater variety of pathogenic strains. In addition, the HOCl used in this study can be made as a neutral pH and at a higher concentration than the previous product [6, 7].

 Pathogenic microbes have been isolated from slaughterhouse and feedlots as well as food [5, 11, 12]. Especially, contamination of pathogens such as Salmonella spp. and E. coli in manufacturing process related meat is known to hazardous factors threaten public health. Therefore, effective disinfectants against pathogenic microbes would be highly desirable.

 HOCl is 80 times more effective as a sanitizing agent than the equivalent concentration of OCL- [13, 15]. HOCl, the most effective form of chlorine compounds, kills microbial cells. Molecules that have highly nucleophilic sites are known to react rapidly with HOCl. Cellular components with these nucleophilic sites include porphyrins and hemes, ferredoxin-like iron-sulfur centers, purine and pyrimidine bases, conjugated polyenes, amines, amino acids and sulfhydryl groups [1]. The oxidation of these components by HOCl results in the loss of physiological functions. During HOCl stress in E coli, the loss of catalytic function of sulfhydryl enzymes and a decrease in anti- oxidants such as glutathione have been suggested to be bactericidal events [1, 8]. HOCl has also been found to disrupt oxidative phosphorylation [3], metabolic pathways involved in ATP utilization or generation [2], and other membrane-associated activities [4]. Furthermore, HOCl can cause DNA damage resulting from the formation of chlorinated derivatives of nucleotide bases [9].

 Based on this study, HOCl solution is recommended as a disinfectant for environmental hygiene and it can the spread of pathogenic microbes using 80 ppm for 1 min. It is suitable for use in public places such as feedlots, slaughterhouses, hospitals, restaurants, schools, transportation hubs and public bathrooms. Before using HOCl, organic material should be removed from the surface.


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