MIRU-VNTR typing of Mycobacterium avium in animals and humans: Heterogeneity of Mycobacterium avium subsp. hominissuis versus homogeneity of Mycobacterium avium subsp. avium strains

Epidemiological studies on Mycobacterium avium are requisite for revealing infection sources and disease transmission. They are based upon genotyping methods like RFLP and MIRU-VNTR. In our study, MIRU-VNTR typing was applied to 121 previously RFLP typed M. avium field isolates to compare the discriminatory power of both methods. The applicability of MIRU-VNTR typing was studied for isolates from a limited geographic area, namely 41 M. avium subsp. avium and 80 M. avium subsp. hominissuis isolates. Among the former, exhibiting 12 IS901 RFLP types, five MIRU-VNTR types were found with discriminatory index (DI) of 0.716. Among the latter, exhibiting 56 IS1245 RFLP types, 18 MIRU-VNTR types were found with DI of 0.866. Concomitant use of both methods increased DI to 0.981 and 0.995, respectively. MIRU-VNTR typing employing the selected markers provided discernible discrimination among M. avium subsp. hominissuis isolates, but more discriminative markers are needed for M. avium subsp. avium isolates.