Short CommunicationCommercial and Homemade Extremely Dilute Hypochlorous Acid Solutions Are Bactericidal Against Staphylococcus aureus and Escherichia coli In Vitro
Introduction
Chlorine is a potent, rapidly acting, short-term disinfectant. However, because chlorine is a gas, it has little practical use. Instead, many compounds that release chlorine find wide application, including hypochlorite and organic and inorganic chloramines. Sodium hypochlorite (NaOCl) is one of the most frequently used chloro-releasing agents used in the field of chemical disinfection; hypochlorous acid (HClO) is the main active ingredient of most household bleaches and cleansers. HClO has a broad antimicrobial spectrum covering bacteria, mycobacteria, bacterial spores, viruses, algae, and protozoa. In human medicine, hypochlorite solutions diluted in water or saline have been used for vaginal, bladder, and urethral irrigations, control of athlete's foot and as infection prophylaxis in the management of burns [1].
Many over-the-counter products are available for use by horse owners for the treatment of wounds in horses. In the last few years, an over-the-counter hydrochlorous acid preparation has been made available (Vetericyn VF Liquid, Innovacyn, Inc, Rialto, CA). Similar products are marketed as a medical device in the human market, but there has been no approval granted for the veterinary product, by the US Food and Drug Administration (FDA), as there are no current requirements by the FDA for animal device clearance [2].
Healing of wounds is thought to be enhanced by decreasing the bacterial burden; however, the need for antimicrobial treatments in wound management is not consistently supported by experimental evidence. Nevertheless, countless topical agents have been used in an effort to prevent wound infection and decrease surface contamination. Unfortunately, the majority of such preparations may be locally toxic and have limited to no proven effectiveness in enhancing wound healing [3].
The first objective of this study was to evaluate the antibacterial effect of a low concentration of hypochlorous acid solution (HClO, 0.011%) against two common bacteria, Escherichia coli and Staphylococcus aureus, in vitro. The second objective of the study was to compare the commercial product to that of a homemade solution (HClO, 0.012%).
Section snippets
Materials and Methods
One bottle of the commercially available aqueous preparation was purchased at a retail tack and pet supply store. The preparation consists of electrolyzed water (H2O, 99.816%), hypochlorous acid (HClO, 0.011%), sodium chloride (NaCl, 0.023%), and sodium phosphate (NaH2PO/NaH2PO4, 0.015%). The pH of the buffered solution was 6.9.
In an effort to duplicate the concentration of HClO in the commercial preparation, the amounts of necessary ingredients (distilled water and bleach) were calculated. A
Results
In trial 1 (commercial solution), no growth of either bacteria was seen in test solutions containing the commercial HClO product after 24 and 48 hours of incubation. Bacterial growth was seen in all control samples.
In trial 2 (commercial solution), no growth of E. coli was seen at either 500 or 1,000 μL. No growth of S. aureus was seen at 1,000 μL, but growth was present at 500 μL. Bacterial growth was present on all control samples.
In trial 3 (homemade solution), no growth of either bacteria
Discussion
Hypochlorous acid has been recognized as a microbicide since at least 1915 [4]. Dakin's solution has been recognized as a wound disinfectant for nearly a century and has been shown to kill pathogenic microorganisms with minimal cytotoxicity [5]; however, its concentration, 0.5% HClO [6], is much higher than that of the tested solutions. HClO is a potent oxidant, and the bactericidal action appears to be primarily related to the destruction of cellular electron transport chains and the adenine
Conclusions
This study showed that single samples of extremely dilute solutions of HClO are bactericidal in vitro for two common equine pathogens. The study assumes that the commercial samples are consistent; if manufacturing standards are not consistent, the results may differ between individual bottles of the product. Given the low cost and easy availability of ingredients, as well as myriad uses in human medicine, it would seem that there are ample reasons for investigation of the use of such extremely
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