EPIDEMIOLOGY OF INFECTION BY NONTUBERCULOUS MYCOBACTERIA .2. GROWTH AND SURVIVAL IN NATURAL-WATERS

Abstract

Nontuberculous mycobacteria belonging to the Mycobacterium avium-M. intracellulare-M. scrofulaceum (MAIS) group grew in the laboratory in natural waters from the eastern USA without added substrates. Growth rates and maximum yields were equivalent for waters from the northeastern and the southeastern states and for waters from which MAIS were and were not recovered. Thus no specific nutrient(s) occurred in the waters of the southeastern USA that could account for a greater frequency of isolation of MAIS organisms from that region. Temperature is apparently a factor influencing the number of MAIS organisms in waters because the MAIS strains tested grew poorly, if at all, below 15.5.degree. C, and the number may have decreased in natural waters incubated at temperatures of .ltoreq. 9.4.degree. C for as long as 30 days. Because the northeastern USA has fewer days with water temperatures above 15.5.degree. C and more below 9.4.degree. C compared with waters in the southeastern USA, MAIS organisms have a shorter growing season and longer periods of decline in the northeast. MAIS organisms grew poorly, if at all, in natural waters approaching the salinities of sea water, which may explain the lower recovery of these mycobacteria from ocean waters relative to fresh and brackish waters. The great area of the coastal ocean water and the predominance of sea surf and foam, which generate marine aerosols, do not rule out the ocean as a source of infection.