Using hypochlorous acid to disinfect from bloodborne pathogens
We often talk about how hypochlorous acid (HOCl) can be used for a wide variety of purposes in healthcare settings. However, in a hospital the efficacy of a disinfectant against specific pathogens is of paramount importance. Improper or ineffective disinfecting could result in patient harm or death!
Some of the most high-risk pathogens are bloodborne illnesses such as HIV, hepatitis, and malaria. These can be difficult to eradicate and often require their own specific hospital cleaning protocol. Items that come in contact with blood should always be sanitized and then sterilized if possible. There is little existing research on the use of HOCl as a sanitizer against bloodborne pathogens, but the few studies that do exist have shown positive results.
For example, a research study in Japan in 2003 found that electrolyzed water could effectively inactivate dried HIV-1. They did their tests with acidic electrolyzed water (pH 2, ORP 1,053 mV), which contains more chlorine gas than hypochlorous acid but is chemically similar. The active ingredient is chlorine, which is equally effective (if not more) at a neutral pH.
Another Japanese study done in 2003 found that acidic electrolyzed water was also effective in inactivating Hepatitis B and C from endoscopes. This study found that the determining factor in successful sanitization with HOCl (in this particular situation) was to first manually clean all endoscopes with a brush. This is not new information, as we already know that the presence of any organic material greatly reduces the oxidative power of HOCl, but it’s a good reminder! The first step to any good sanitation protocol is a vigorous cleaning process.
More recently, a study done in 2022 in the Journal of Medical Virology tested HOCl as a sterilizer for non-autoclavable medical instruments contaminated with HPV. The HOCl concentration was 180 ppm and the results showed that after 15 seconds, all strains of HPV (except HPV 16 on ultrasonic probes) were inactivated to >4 Log reduction (99.99% killed). HPV 16 was reduced to 99.99% after 5 minutes of soaking in HOCl. This proves HOCl’s efficacy as a sanitizer for bloodborne pathogens, particularly when autoclaving is not possible or available (eg; in extremely remote locations or during natural disasters).
The CDC recommends that all non-critical patient care instruments/devices be first manually cleaned to remove organic material and then disinfected with an approved sanitizer. Chlorine is on the list of CDC approved sanitizers in the form of hypochlorite; however, this can be interchanged with hypochlorous as long as the directed ppm is met (which is generally listed as >100 ppm or 500-650 ppm).
The CDC approves hypochlorite as an intermediate and low-level disinfectant for hospital instruments and surfaces (the final step before sterilization.) Hypochlorite (or free available chlorine) is approved for use on hard surfaces at 100 ppm (>1 minute contact time). For catheters, rubber/polyethylene tubing, and lensed or hinged instruments, hypochlorite can be used at >650 ppm.
We like to keep it simple--if you are already using bleach in your hospital, hypochlorous can easily be switched out at the same usage ratio. The only difference will be in the ppm, or chlorine strength. Because HOCl is more effective at a lower ppm than bleach, you rarely need to use more than 500 ppm. For the majority of hospital cleaning purposes, 500 ppm will suffice. If you are using HOCl for high-risk sanitization, such as with non-autoclavable medical instruments or to target a specific pathogen, then it might be appropriate to use >500 ppm as needed.
Cover image credit: Photo by Piron Guillaume on Unsplash
Sources
https://www.cdc.gov/infectioncontrol/guidelines/disinfection/tables/table1.html
2003 Japan study on HOCl and HIV
2023 Journal of Medical Virology endoscope study
2003 Japan study on HOCl and HPV
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