Bactericidal Mechanism of Chlorous Acid Water in the Inactivation of Non-Tuberculous Mycobacteria

The global prevalence of pulmonary infections caused by non-tuberculous Mycobacteria (NTM), particularly the Mycobacterium avium complex (MAC), is increasing. Since NTM are ubiquitous in moist environments and resistant to standard disinfectants, this study evaluated the efficacy of chlorous acid water (CAW) against them. CAW demonstrated superior sanitizing effects compared to sodium hypochlorite (NaClO). It efficiently inactivated NTM at free available chlorine concentrations of 25 mg/L without organic matter and 100 mg/L with organic matter. In contrast, NaClO at 1000 mg/L failed to inactivate NTM in the presence of organic matter. MAC showed higher resistance to both agents compared to other NTM species. Mechanistically, the bactericidal effect of CAW did not correlate with DNA degradation. While prolonged exposure induced DNA damage, the primary mode of action was identified as a reduction in membrane potential, ATP production, and reactive oxygen species levels without altering cell morphology. These results indicate that CAW inactivates NTM effectively by damaging membrane components and the respiratory chain, rather than targeting DNA.