Abstract
The pneumococcal genome is variable and there are minimal data on the influence of the accessory genome on phenotype. Pneumococcal serotype 14 sequence type (ST) 46 had been the most prevalent clone causing pneumonia in children in Taiwan. A microarray was constructed using the genomic DNA of a clinical strain (NTUH-P15) of serotype 14 ST46. Using DNA hybridization, genomic variations in NTUH-P15 were compared to those of 3 control strains. Microarray analysis identified 7 genomic regions that had significant increases in hybridization signals in the NTUH-P15 strain compared to control strains. One of these regions encoded PblB, a phage-encoded virulence factor implicated (in Streptococcus mitis) in infective endocarditis. The isogenic pblB mutant decreased adherence to A549 human lung epithelial cell compared to wild-type NTUH-P15 strain (P = 0.01). Complementation with pblB restored the adherence. PblB is predicted to contain a galactose-binding domain-like region. Preincubation of NTUH-P15 with D-galactose resulted in decreases of adherence to A549 cell in a dose-dependent manner. Challenge of mice with NTUH-P15, isogenic pblB mutant and pblB complementation strains determined that PblB was required for bacterial persistence in the nasopharynx and lung. PblB, as an adhesin mediating the galactose-specific adhesion activity of pneumococci, promote pneumococcal clonal success.
Highlights
Clone no. 1 2 3 4 5 gene SPP 0074 SPP 0075 SPCG 0649 SPCG 0650 SPP 1758 SPP1759 SPT 0236 SP 0167 SP 0168 SP 0169 SP 0170 SP 0171 SP 0172 SP 0173 SP70585 1097 SP70585 1098
Blast searches of clone 1 identified that clone 1 contained genes with similarity to the adjacent loci SPP_0074 and SPP_0075 of S. pneumoniae P1031 (Table 1); the products of these genes exhibit similarity to a host specificity protein and PblB, respectively (Fig. 1)
Our findings identified that pblB, a phage-encoded protein in a successful invasive pneumococcal clone, contributes to pneumococcal adhesion through binding to galactose-containing glycoconjugates on lung epithelial cell
Summary
Clone no. 1 2 3 4 5 gene SPP 0074 SPP 0075 SPCG 0649 SPCG 0650 SPP 1758 SPP1759 SPT 0236 SP 0167 SP 0168 SP 0169 SP 0170 SP 0171 SP 0172 SP 0173 SP70585 1097 SP70585 1098. The successful global expansion of the Spain9V-3 clone (ST156) was attributed to the presence of rlrA pilus islet, which promotes colonization as well as virulence of S. pneumoniae[8]. Pneumococcal serine-rich repeat protein (PsrP), a pathogenicity island encoded adhesin, was positively correlated with the ability of S. pneumoniae to cause invasive disease[9]. We constructed a microarray based on the genome of an endemic, multi-resistant serotype 14 ST 46 clone[2]. Genomic variation among a clinical strain (NTUH-P15) of serotype 14 ST 46 and 3 non-clonal-expansion strains of pneumonia were compared by DNA microarray hybridization to obtain insights into the mechanism of expansion of the serotype 14 ST 46 clone in Taiwan
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