Sequence differences between capsular locus 11A and 11D cluster mainly in the insertion sequence (IS1202) flanking the 5′ end of the locus and in the wcjE gene, encoding a putative O-acetyl transferase. While the biochemical VS-4718 chemical structure structure of the type 11A capsule is known [32], that of type 11D capsule has not been elucidated, therefore it is unclear which structural

difference underlies the immunological difference. In addition, serotype 11D is quite rare, since no isolates of this serotype appear in the MLST database or in recent large datasets. On the other hand, recent findings indicate that serotype 11A has a high degree of genetic heterogeneity. A new pneumococcal serotype, designated 11E, has been recently discovered among isolates previously identified as serotype 11A, and has been found to be associated with a mutated or disrupted wcjE gene [10]. On the basis of these data and our results it appears that serotype 11 is genotypically variable and

it is likely that its typing scheme will be reconsidered in the near future. Most of the other pneumococcal virulence factors are surface-exposed proteins such as the choline-binding proteins (CBPs) and the LPXTG proteins. Ten different CBPs genes have been recognized in the genome of AP200, including pspA and pspC, which play an important role in pneumococcal pathogenicity [33, 34]. Both these proteins are characterized by an extensive polymorphism, likely reflecting the immunological selective pressure to which they are exposed. selleck kinase inhibitor According to the classification of Hollingshead et al. [35], that defines 6 immunologically-relevant

monophyletic groups (clades) on the basis of the divergence of the PspA central region, AP200 PspA CYTH4 belongs to clade 3. Similarly, the PspC protein has been divided into 11 major groups due to unique sequence blocks [36]. According to this classification, AP200 PspC corresponds to PspC3. The LPXTG family includes proteins anchored to the peptidoglycan cell wall by the action of a sortase transpeptidase that recognises the motif LPXTG. Pili, recently discovered in pneumococci, are composed of LPXTG-type protein subunits, and can be of 2 types, encoded by 2 different islets, PI-1 and PI-2 [24, 37]. AP200 carries PI-2, that is found in 20% of pneumococci only and has been demonstrated to mediate adherence to the epithelial cells of the respiratory tract [24]. The PI-2 region in AP200 is identical to that of serotype 1 PN110 selleck chemical strain [24], being flanked by the hemH and pepT genes, but is contained in the 163 kb inversion. Of the two other sequenced serotype 11A ST62 strains, only SP11-BS70 carries PI-2. A recent investigation on the prevalence of PI-2-carrying pneumococcal isolates in Atlanta, USA, highlighted the increase of serotypes carrying PI-2 among emerging non-PCV7 serotypes, including serotype 11A [38]. Four large surface zinc metalloproteinases have been described in S.