While PI-1 had a widespread distribution, the presence of PI-2a and PI-2b was non-random. Within CC’s, little variation was observed in the frequency of PI-2a and PI-2b except in CCs 1 and 7, which had a range of PI profiles. PI-1 frequencies, however, varied within and across CCs, particularly in human strains (Figure 3). Most CC-23 strains (n = 18; 60%), for example, lacked PI-1, whereas virtually all CC-19 (n = 88; 100%) and CC-17 (n = 69; 99%) strains had PI-1 with one

PI-2 variant. The only CC-17 strain without PI-1 (ST-83) originated from Z-IETD-FMK nmr a bovine. Among strains of the same ST, multiple profiles were observed in two CCs. Within ST-1, all strains had PI-1/PI-2a (n = 14) or PI-2b (n = 7), while ST-2 strains had three profiles: PI-1/PI-2a (n = 6), PI-1/PI-2b (n = 1), and PI-2a only (n = 1). ST-23 strains had PI-2a with (n = 4) and without PI-1 (n = 9). Figure 3 Frequency of pilus island (PI) types by clonal complexes (CCs). All 295 stains were screened for the presence of PI-1, PI-2a, and PI-2b using multiplex PCR. The frequency of each PI is illustrated across CCs, which are listed in tree order as determined using the Neighbor-Joining CDK inhibitor drugs method (Figure 1). Strains representing STs that did not belong to one of the seven CCs were combined into a group of singletons. Nine

PI-2a/PI-2b BP gene alleles were identified (Additional file 1: Figure S1) and varied across strains (Figure 4). Strains with PI-2a frequently had gbs59 alleles 1 (n = 89; 30%) or 6 (n = 32; 11%) while strains with PI-2b had san1519 alleles 2 (n = 69; 23%) or 3 (n = 45; 15%). Little variation was observed in gbs59 among CC-19 strains and in san1519 among CC-17, -61, and -67 strains. The remaining CCs were more diverse. CC-1 strains, for example, had five of six gbs59 alleles. Figure 4 Frequency of pilus

island (PI) backbone protein genes by clonal complex (CC). The distribution of A) six gbs59 alleles specific for PI-2a is illustrated in 161 group B streptococcal strains and oxyclozanide B) three san1519 alleles specific for PI-2b in 113 strains belonging to the seven CCs. In each figure, the CCs are listed in tree order based on the Neighbor-Joining phylogeny (Figure 1). Singletons (n = 21) were excluded from this analysis. Epidemiological associations and host specificity Bovine strains were less variable than human strains with respect to the presence of specific PIs. All bovine strains representing the 18 bovine-specific lineages lacked PI-1, though PI-1 was present in six of the seven bovine strains classified as STs 1, 2, 19, and 23 that contain mostly human-derived strains. Among the 45 PI-1-negative bovine strains, the integration site was occupied by a genetic element other than PI-1 in 18 (40%); the site was intact in the remaining 27. Because a subset of these strains had genomes available, the lack of PI-1 was confirmed in 10 of the 18 strains examined.