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THE EFFECT OF TEMPERATURE ON THE GROWTH OF MYCOBACTERIUM AVIUM COMPLEX (MAC) ORGANISMS
Covert, T C., A. L. Reyes, M R. Rodgers, AND A P. Dufour. THE EFFECT OF TEMPERATURE ON THE GROWTH OF MYCOBACTERIUM AVIUM COMPLEX (MAC) ORGANISMS. Presented at American Society of Microbiology 101st General Meeting, Orlando, FL, May 20-24, 2001.
1)Develop an improved method(s) for isolating and/or detecting nontuberculous mycobacteria from potable water. 2)Determine the best DNA fingerprinting method to use to determine genetic relatedness with clinical and environmental isolates.
MAC organisms are able to grow, persist, and colonize in water distribution systems and may amplify in hospital hot water systems. This study examined the response of MAC organisms (M. avium, M. intracellulare, and MX) to a range of temperatures commonly associated with drinking water and hot water distribution systems. Clinical and environmental isolates (n=30) in 7H9 broth were exposed to temperatures at 2 degree increments between 13 degrees C and 65 degrees C for two weeks. Relative growth rates, minimum, maximum, and optimum growth temperatures for all MAC organisms ranged from 28 degrees C to 38.5 degrees C. M. avium strains showed a mean optimum growth at 34.5 degrees C whereas M. intracellulare and MX grew best at mean temperatures of 31.5 degrees C and 30 degrees C, respectively. Ninety per cent of M. avium isolates were capable of survival at temperatures of 49 degrees C or greater, the temperature used in many institutional hot water systems. Only 10% of the M. intracellulare and MX isolates were capable of survival at 49 degrees C or greater. Growth temperature profiles for MAC organisms indicate that most M. avium strains may survive in hot water plumbing systems whereas the majority of M. intracellulare and MX strains may not survive temperatures greater than 49 degrees C. The optimum growth temperature of MX differed significantly from M. avium but not from M. intracellulare.