Variable-Number Tandem-Repeat Analysis of Respiratory and Household Water Biofilm Isolates of “Mycobacterium avium subsp. hominissuis” with Establishment of a PCR Database

“Mycobacterium avium subsp.hominissuis ” is an important cause of pulmonary disease. It is acquired from environmental sources, but there is no methodology for large population studies. We evaluated the potential of variable-number tandem-repeat (VNTR) analysis. Clinical and household biofilmM. avium isolates underwent molecular identification. Testing for IS901 was done to separateM. avium subsp.avium fromM. avium subsp.hominissuis . VNTR types were defined using VNTR loci, and subtyping was performed using 3′hsp65 and internal transcribed spacer (ITS) sequencing. Forty-nine VNTR types and eight subtypes ofM. avium subsp.hominissuis (IS901 negative) were identified among 416 isolates ofM. avium from 121 patients and 80 biofilm sites. Of those types, 67% were found only among patient isolates, 11% only among household water isolates, and 23% among both. Of 13 VNTR types that included ≥4 patients, the majority (61.5%) represented geographic clustering (same city). Most VNTR types with multiple patients belonged to the same 3′hsp65 sequence code (sequevar). A total of 44 isolates belonging to fourM. avium subsp.hominissuis VNTR types (8%), including three with the rare Mav-F ITS sequence and 0/8 subspecies, produced amplicons with IS901 PCR primers. By sequencing, all 44 amplicons were not IS901 but ISMav 6, which was recently observed in Japan but had not been previously described among U.S. isolates. VNTR analysis ofM. avium subsp.hominissuis isolates is easier and faster than pulsed-field gel electrophoresis. Seven VNTR loci separated 417 isolates into 49 types. No isolates ofM. avium subsp.avium were identified. The distributions of the VNTR copy numbers, the allelic diversity, and the low prevalence of ISMav 6 differed from the findings for respiratory isolates reported from Japan.