STRAIN-SPECIFIC VARIATION IN THE DNAJ GENE OF MYCOBACTERIA

The polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique was evaluated for species identification among my cobacteria by analysis of the dnaJ gene. Nine clinical isolates of Myc obacterium tuberculosis with different fingerprint patterns all gave t he same distinct SSCP banding pattern and could be distinguished from other mycobacteria, such as M. avium. In contrast, considerable strain -specific dnaJ gene variations mere observed amongst 42 clinical isola tes of M. avium and 13 other atypical mycobacterial strains. Only 62% of the M. avium isolates hybridised to an M. avium-specific probe and only 14% could be identified correctly as M. avium by both probe and r estriction fragment length polymorphism analysis. This finding was sup ported by direct sequence analysis. Variations were also observed in M . gordonae and M. scrofulaceum isolates. Computerised analysis of M. a vium samples broadly identified three dusters. Results suggest that al though the SSCP procedure may be useful for distinguishing M. tubercul osis from other mycobacteria, this technique applied to the dnaJ gene may not be suitable for strain identification. The results stress the importance of testing a large collection of clinical isolates before n ew molecular procedures are introduced into routine laboratories.