Bethe and colleagues reported that PrtA is a highly conserved virulence factor of Streptococcus pneumoniae, and might be a promising candidate for a protein-based
vaccine . (ii) Autolysin, the autolysin encoded by cwh is also a reported virulence-associated factor in SS2 . Most bacteria possess several autolysins that are able to degrade their cell walls, and are implicated in various biological functions Ilomastat including cell separation, cell wall turnover, restructuring of cell walls, and bacterial autolysis. In addition, certain autolysins have also been reported to contribute to the pathogenicity of gram-positive bacteria. For example, an intact autolytic function is required for the full virulence of Streptococcus pneumoniae . (iii) protein TRAG, TRAG is a component of the type IV secretion system (T4SS), a virulence-associated pathway of SS2 . The bacterial T4SS, which is widely distributed among the gram-negative and -positive bacteria and is ancestrally related to bacterial conjugation machines (which mediate protein and gene transfer), contributes to pathogenicity . Analysis of the in vivo gene expression profiles Strain ZY05719 was selected for real-time PCR analysis because it is one of the strains isolated from the 2005 SS2 outbreak in China; ZY05719 was also used for constructing the genomic library. Of the 48 putative
IVI genes, 10 (ss-1616, trag, nlpa, srt, cwh, hprk, ysirk, ss-1955, Belnacasan cost sdh, ss-1298) were selected for further analysis of gene expression by real-time PCR. We selected these genes based on their putative functions, such as involvement in cell structure, metabolism, regulation, and transport, in order to maximize the variety of genes
chosen for further analysis. The in vitro expression of these 10 putative IVI genes was observed in early lag phase, log phase, late log phase, and check details stationary phase of growth, with the highest level of expression occurring at late log phase (data not shown). Before comparing the expression of these 10 putative IVI genes under the in vitro condition, they were first tested under in vivo conditions (expression after challenge with bacterial cells via intravenous inoculation measured at 12, 24, and 36 h pi). All of the putative IVI genes were expressed in vivo under the conditions tested (data not shown). With the exception of ysirk and ss-1955, which were expressed at 12 h pi but not at 24 and 36 h pi, and ss-1298, which was expressed until 36 h, the remaining 7 IVI genes were expressed at 12, 24 and 36 h post-inoculation in vivo. The aim of this study was to identify the genes whose expressions are upregulated in vivo; therefore, we determined the in vivo gene expression relative to the highest level of expression in vitro.