In vivo characterization of the psa genes from Streptococcus pneumoniae in multiple models of infection

Abstract

Differential fluorescence induction technology was used to identify promoters of Streptococcus pneumoniae genes that are expressed during lung infection of the mouse. Among the promoter clones that were identified multiple times was the psa promoter, which drives expression of the psaBCA operon. These genes have been identified previously and shown to encode a manganese permease system as well as play a role in the virulence of this organism. Mutations in psaB, psaC or psaA result in growth limitation in low manganese. The expression of the psa operon was examined in vivo and the virulence of deletion mutants of psaB, psaC, psaA and psaBCA was assessed in four different animal models of infection. The psa promoter was induced more than ten-fold in vivo using an intraperitoneal chamber implant model. The psaB, psaC and psaA mutants were completely attenuated in systemic, respiratory tract and otitis media infections. In addition, these mutants were unable to grow in an implanted peritoneal chamber, but growth was restored by the addition of manganese to the chambers.

Genetic Characterization and Role in Virulence of the Ribonucleotide Reductases of Streptococcus sanguinis

“…A previous study from our group showed that the high affinity manganese transporter, SsaB, is essential for O 2 tolerance and endocarditis virulence in S. sanguinis (26). This mirrored earlier findings showing that orthologs of this transporter are essential for endocarditis caused by other oral streptococci (29,30) for pneumonia, bacteremia, and otitis media caused by Streptococcus pneumoniae (31)(32)(33)(34), for bacteremia caused by S. pyogenes (35), and for mastitis caused by Streptococcus uberis (36). It is known that Mn II contributes to O 2 tolerance in part by serving as a cofactor for the superoxide dismutase SodA.…”

Versatility of pneumococcal surface proteins

“…In contrast to some Gram-negative pathogens, the virulence genes of S. pneumoniae are not generally clustered together. Wholegenome microarray analysis has depicted the differential expression of genes under invasive and non-invasive conditions, and cross-linking of the data with the results of STM and DIF screens provides an extended list of putative virulence factors Orihuela et al, 2004;Marra et al, 2002). These virulence factors can be regulated by one-component regulatory systems, including luxS, rlrA, regM/R and mgrA, or by one of the 14 TCSs that have been identified in S. pneumoniae (Hoskins et al, 2001;Tettelin et al, 2001).…”

“…This is consistent with the finding that mucosal immunization of mice with PsaA is highly protective against pneumococcal carriage (Johnson et al, 2002). Differential fluorescence induction (DIF) analysis has demonstrated the upregulation of the psa promoter of the psaBCA operon during lung infections, and microarray analysis has demonstrated that psaA is upregulated during attachment of pneumococci to nasopharyngeal cells (Marra et al, 2002;Orihuela et al, 2004).…”

“…The pneumococcal surface adhesin A (PsaA) is the substrate-binding lipoprotein of an ABC-type manganese-transport system (Dintilhac et al, 1997). Mutations in psaA cause pleiotropic effects, including reduced adherence of pneumococci to host cells, attenuation in an intranasal and intraperitoneal mouse infection model, and increased sensitivity to oxidative stress (Marra et al, 2002;Tseng et al, 2002). Since the detection of these pleiotropic effects, it has been assumed that PsaA does not itself function as an adhesin; however, a recent report has demonstrated that antibodies against PsaA reduce the adherence of pneumococci to nasopharyngeal epithelial cells (RomeroSteiner et al, 2003).…”

Characterizing the conformational dynamics of metal-free PsaA using molecular dynamics simulations and electron paramagnetic resonance spectroscopy

“…S. pneumoniae is a causative agent of bacterial pneumonia, meningitis, septicaemia and otitis media [5,6] and is the foremost bacterial pathogen associated with mortality in children less than 5 years old worldwide [7]. Manganese has crucial roles in S.…”