Comparative use of DNA probes for Mycobacterium avium and Mycobacterium intracellulare and serotyping for identification and characterization of animal isolates of the M. avium complex.

Commercially available DNA probes for the Mycobacterium avium complex (MAC) were compared with conventional identification and serotyping of animal isolates of MAC. DNA hybridization of 44 strains of mycobacteria showed a test specificity of 100% and sensitivity of 100%. Hybridization of 12 serotype strains showed that serotypes 1-6 and 8-11 hybridized with the M. avium probe and serotypes 7 and 14 hybridized with the M. intracellulare probe. All of the 42 bovine and porcine isolates of MAC consisting of serotypes 1-6 and 8-10 hybridized only with the M. avium probe. Two strains originally identified as MAC by biochemical tests turned out to be negative in the hybridization test and were identified as rapid growers in gas chromatography analysis of fatty acids. This study furthermore indicates that MAC infections in animals in Norway are mainly caused by M. avium probe positive strains.