Plasmid DNA profiles as epidemiological markers for clinical and environmental isolates of Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum.

Plasmid DNA was isolated, and profiles of a variety of clinical and environmental isolates of Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum (MAIS) were compared to determine whether plasmid DNA content would be useful as an epidemiological marker for these environmental pathogens. Since plasmids are common in clinical isolates and are stable during culture and exposure to NaOH, plasmid DNA analysis appears to be a suitable epidemiological tool. Based on the high frequency of plasmids in only clinical (56%) and aerosol (75%) isolates and low frequencies in soil (5%), dust (7%), sediment (less than 6%), and water (25%) isolates, the data suggest that MAIS-laden aerosols generated over waters of the southeastern United States are a likely source of human infection.