Distribution of the three PGRS types through sSNP-based genetic clusters and PGG groups. The Phylogenetic tree of M. tuberculosis isolates from New York and New Jersey shows the relative distribution of PGRS types 1 (PGRST1; +/-), 2 (PGRST2; +/+), and 3 (PGRST3; -/-) with respect to the synonymous single-nucleotide (sSNP)-defined 9 major genetic clusters (I, II, IIA, and III to VIII) and PGG grouping. The 36 sSNP-based phylogenetic tree was constructed as described by Gutacker et al. . The data clearly indicate that the PE_PGRS17/PE_PGRS18-associated gene conversion event occurs multiple times mainly in PGG2 strains.