Disinfectant Effects of Hot Water, Ultraviolet Light, Silver Ions and Chlorine on Strains of Legionella and Nontuberculous Mycobacteria

The disinfectant effects on Legionella and nontuberculous mycobacteria of hot water, ultraviolet light, silver ions and chlorine, were evaluated. The bacterial strains Legionella pneumophila ATCC33152 and Mycobacterium avium ATCC25291 and strains of L. pneumophila and M. avium which had been isolated from a 24 h bath, were examined for their resistance to treatments. All strains were killed within 3 min on exposure to hot water at 70 degrees C and exposure to ultraviolet light at 90 mW.s/cm2. The strains of L. pneumophila tested were killed within 6 h on exposure to a solution of silver ions at 50 micrograms/l. The number of viable cells of strains of M. avium fell from 10(5) CFU/ml to 10(3) CFU/ml after exposure to an aqueous solution of silver ions at 100 micrograms/l for 24 h. Chlorine effectively killed strains of Legionella which were exposed to an aqueous solution of chlorine at 2 mg/l within 3 min, but strains of Mycobacterium survived exposure to chlorine at 4 mg/l for more than 60 min.