Mycobacterium avium subspecies
hominissuis (MAH), a nontuberculous mycobacterium, is sometimes detected in drinking water systems and bathrooms where it forms biofilm. MAH causes pulmonary disease, disseminated infections, and lymphadenitis in small children, transmitted from the environment to the human body
via ingestion and inhalation of contaminated water and aerosols. Therefore, methods for disinfecting environmental biofilm-forming MAH are essential. Sodium hypochlorite is a chlorination agent widely used to disinfect water in drinking water systems and swimming pools, and chlorine dioxide also has potent bactericidal activity. However, the bactericidal activity of chlorine compounds against biofilm-forming MAH remains unclear. Therefore, we compared the disinfectant activities of sodium hypochlorite and chlorine dioxide against planktonic growing and biofilm-forming MAH cells. Concentrations of 100 and 1000 mg/L of sodium hypochlorite killed planktonic MAH cells (about 10
5 CFU/mL) within 30 and 5 min, respectively, whereas 10 mg/L of chlorine dioxide killed these cells within 5 min. MAH biofilm had cell counts of up to 10
8–10
9 CFU/well. Although 1000 mg/L of hypochlorite applied to MAH biofilm killed only 90% of these cells in 30 min, 100 mg/L of chlorine dioxide killed 99.99% of cells in 30 min. Therefore, chlorine dioxide is superior to sodium hypochlorite for the eradication of environmental MAH. However, MAH biofilm caused reduction in the bactericidal activity of chlorine-based disinfectants. Therefore, structural and functional analyses of MAH biofilm prepared using environmental isolates may facilitate eradication of environmental bacilli.
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