Genotypic characteristics of Mycobacterium avium subsp hominissuis strains

Mycobacterium avium are typical environmental, non-tuberculosis microorganisms that occasionally cause mycobacteriosis, an infectious disease in wild and domestic animals, birds, and humans. Here, we report the results of the first study on the genetic diversity of the Russian population of M. avium. A total of 85 M. avium subsp. hominissuis (MAH) clinical strains were isolated from patients (including 30 HIV-positive individuals) with mycobacteriosis in St. Petersburg, 2008-2011. The identification of the microorganisms was carried out using biochemical tests and the PCR detection of the mobile elements IS901 and IS900, as well as of the polymorphism of restriction fragments of the hsp65 gene. The genetic diversity of the isolates was evaluated by VNTR typing based on eight variable-number tandem repeats (VNTRs) (292, X3, 25, 47, 3, 7, 10, and 32 [Thibault et al., 2007]). The MAH population studied was characterized by 15 VNTR types, including nine unique patterns and six clusters of isolates with identical eight-digit profiles. The largest clusters (22221128 and 24221128) included 45 (59.2%) and 15 (19.7%) isolates, respectively; the others contained 2-7 strains. The strains of the cluster 2533112'8 possessed a truncated TR10 locus (allele 2'). Taking into account the absence of the epidemiological links between the patients and the fact that the infection was presumably delivered from the environment, the high rate of clustering of MAH isolates can be explained by the low discriminatory power of the eight-locus VNTR-typing scheme (HGDI 0-0.61).