Characterisation of plasmids extracted from AIDS--associated Mycobacterium avium isolates

The plasmid profiles of 12 Mycobacterium avium strains isolated from 12 different patients with acquired immunodeficiency syndrome were analysed. Plasmids were identified in 9 of these strains. Plasmids were isolated from all 7 serovars 4 and 8 strains, a serovar 20a strain and an untypeable strain, but were not detected in either of 2 serovar 3b strains or an untypeable isolate. Southern blot hybridisations revealed that extracts derived from all of the plasmid-containing strains hybridised to a DNA probe prepared from known mycobacterial plasmid sequences. However, restriction analyses suggest that native plasmids which hybridised to the DNA probe and were similar in mass were not identical.