Chlorous acid inactivates Mycobacterium tuberculosis with much lower available chlorine concentration than sodium hypochlorite.

Mycobacterium tuberculosis is the causative agent of tuberculosis. Globally it is one of the most important bacteria responsible for human mortality. To control tuberculosis proper sterilization of Mycobacterium is important. For sterilization of pathogens, sodium hypochlorite is commonly used. However, M. tuberculosis usually shows high resistance against sodium hypochlorite. In this study, we compared the bactericidal activity of chlorous acid and sodium hypochlorite against M. tuberculosis in the presence or absence of artificial saliva. When 7.0 log CFU/mL of M. tuberculosis was treated with different concentrations of sodium hypochlorite or chlorous acid, it was found that while 20,000 ppm of sodium hypochlorite was needed to reduce the pathogen below the detection limit but for chlorous acid only 5 ppm was required. Furthermore, when the experiment was performed in the presence of artificial saliva, 500 ppm of sodium hypochlorite was needed to reduce the M. tuberculosis below detection limit but for chlorous acid it was 25 ppm. The data indicate that chlorous acid is a more powerful disinfectant than sodium hypochlorite regardless of presence or absence of artificial saliva. Thus, chlorous acid may be used as a useful bactericidal agent to sterilize clinical environment contaminated with M. tuberculosis.