Heat inactivation of Mycobacterium avium-Mycobacterium intracellulare complex organisms in aqueous suspension

Abstract

Isolants from swine and from humans representing serotypes 1, 2, 4, 8, and 10 of the M. avium-M. intracellulare complex were compared for heat tolerance in aqueous suspension. The most heat-resistant isolant found was a serovar 10 isolated from a human. This isolant was examined further to determine the rate of kill at various temperatures and pH's, the effect of meat protein and fat, and the effect of nitrite. Kill rates were not significant at 60°C or below. Decimal reduction values were 4 min or less at 65°C and 1.5 min or less at 70°C. Kill rates were slightly higher at pH values of 6.5 and 7.0 than at 5.5 or 6.0. The water-soluble fraction of wiener emulsion did not alter kill rates, but the saline-soluble fraction protected the organism somewhat. Fat did not affect the survival of the organisms except to eliminate the protective effect of saline extract when the suspension contained 50% fat. The addition of sodium nitrite to the suspension did not alter the heat sensitivity of the organisms.