Intra-subspecies sequence variability of the MACPPE12 gene in Mycobacterium avium subsp. hominissuis.

The PE (Pro-Glu) and PPE (Pro-Pro-Glu) multigene families are unique to mycobacteria, and are highly expanded in the pathogenic members of this genus. We determined the intra-subspecies genetic variability of the MACPPE12 gene, which is a specific PPE gene in Mycobacterium avium subsp. hominissuis (MAH), using 334 MAH isolates obtained from different isolation sources (222 human isolates, 145 Japanese and 77 Korean; 37 bathroom isolates; and 75 pig isolates). In total, 31 single-nucleotide polymorphisms (SNPs), which consisted of 16 synonymous SNPs and 15 nonsynonymous SNPs, were determined through comparison with the MACPPE12 gene sequence of MAH strain 104 as a reference. As the result, the 334 MAH isolates were classified into 19 and 13 different sequevars at the nucleic acid level (NA types) and amino acid level (AA types), respectively. Among the 13 AA types, only one type, the AA02 type, presented various NA types (7 different types) with synonymous SNPs, whereas all other AA types had a one-to-one correspondence with the NA types. This finding suggests that AA02 is a longer discernible lineage than the other AA types. Therefore, AA02 was classified as an ancestral type of the MACPPE12 gene, whereas the other AA types were classified as modern types. The ubiquitous presence of AA02 in all of the isolation sources and all different sequevars classified by the hsp65 genotype further supports this classification. In contrast to the ancestral type, the modern types showed remarkable differences in distribution between human isolates and pig isolates, and between Japanese isolates and Korean isolates. Divergence of the MACPPE12 gene may thus be a good indicator to characterize MAH strains in certain areas and/or hosts.