Each of these two clusters was associated with a particular pattern of surface protein expression. This previous study also separated the bovine and human CC17 strains [50]. These results are consistent with an ancient divergence of these clusters, whereas other observations find more based on MLST analysis suggest that ST-17 strains may have arisen from a bovine ancestor [6]. The lack of a strict correlation between the results of MLST and MLVA may be accounted for by differences in the markers used for MLST (targeting housekeeping

genes) and MLVA (targeting a set of diverse regions that may or may not be conserved). Unlike MLST, MLVA targets several types of markers: genes involved in metabolism, genes associated with virulence and a genomic island.

Indeed, SAG2 is located upstream from the gene encoding the ribosomal protein S10 which is involved in transcription and translation, and SAG3 is located within dnaJ, which encodes a CHIR98014 member of the Hsp70 family, a co-chaperone protein (Hsp40). The SAG21 locus encodes a surface protein involved in virulence, FbsA. The SAG7 locus is located on a genomic island and belongs to a gene encoding a hypothetical protein whose function has not yet been identified, like most of the genes of genomic islands [51]. Clustering based on MLVA data was almost identical with the UPGMA and MST algorithms except for cluster 1. The differences in mathematical calculation between the two methods may account for the observed

differences in AZD2014 supplier strain clustering. This phenomenom has been previously observed in MLVA studies [52]. Some VNTRs for the alpha C protein have already been described in S. agalactiae [41, 53, 54]. One of these VNTRs is involved in regulating gene expression: a pentanucleotide repeat located upstream from the promoter regulates expression in vitro by phase variation. Another is an intragenic VNTR that modifies the size of the alpha C protein, thereby altering its antigenicity and strain virulence [53]. These two VNTR loci were not included in the Pyruvate dehydrogenase MLVA method proposed here, in one case because the small size of the repeat unit (5 bp) complicates the mode of PCR fragment size assessment [19]. The amplicons of the second VNTR locus not included were more than 2000 bp in size, again making it difficult to evaluate repeat number. Tandem repeats were also found in the gene encoding another surface protein, FbsA, which interacts with epithelial cells and is involved in invasion of the central nervous system of colonized neonates. Its ability to bind to fibrinogen depends on the number of repeats of a unit of 16 amino acids present at its N-terminus [55]. A particular number of repeats is associated with the greater potential of the ST-17 strains implicated in neonatal meningitis to adhere to fibrinogen [56].