Growth characteristics of atypical mycobacteria in water and their comparative resistance to disinfectants

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Abstract
With the increasing significance of group IV atypical mycobacteria as etiological agents in a variety of [human] infections, studies were conducted to determine their growth capabilities in water and their comparative resistance to disinfectants used to decontaminate hospital equipment. Isolates of Mycobaterium chelonei (TM strains) from peritoneal fluids of patients and peritoneal dialysis machines were able to multiply in commercial distilled water, with generation times at 25.degree. C ranging from 8-15 h. Levels of 105-106 cells/ml were attained, and these stationary-phase populations declined only slightly over a 1 yr period. TM strains of M. chelonei cultured in commercial distilled water showed survivors in 2% aqueous formaldehyde (HCHO) solutions up to 24 h; in 8% HCHO, only a 2-log reduction in viable counts was observed over a 2-h sampling period. Reference ATCC strains of M. chelonei and M. fortuitum wer rapidly inactivated, with no survivors after 2 h of exposure to 2% HCHO or 15 min of exposure to 8% HCHO. In 2% alkaline glutaraldehyde, TM strains survived 60 min, whereas ATCC strains showed no survivors after 2 min of contact time. All M. chelonei and M. fortuitum strains survived 60 min of exposure to concentrations of 0.3 and 0.7 .mu.g of free Cl/ml at pH 7.