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Characterization of Pneumococcal Genes Involved in Bloodstream Invasion in a Mouse Model.

Mahdi LK, Van der Hoek MB, Ebrahimie E, Paton JC, Ogunniyi AD - PLoS ONE (2015)

Bottom Line: In this manner, we identified 26 genes that were significantly up-regulated in the nasopharynx and 36 genes that were significantly up-regulated in the blood that were common to both strains.Gene Ontology classification revealed that transporter and DNA binding (transcription factor) activities constitute the significantly different molecular functional categories for genes up-regulated in the nasopharynx and blood.Targeted mutagenesis of selected genes from both niches and subsequent virulence and pathogenesis studies identified the manganese-dependent superoxide dismutase (SodA) as most likely to be essential for colonization, and the cell wall-associated serine protease (PrtA) as important for invasion of blood.

View Article: PubMed Central - PubMed

Affiliation: Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia.

ABSTRACT
Streptococcus pneumoniae (the pneumococcus) continues to account for significant morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteremia and meningitis, as well as less serious infections such as sinusitis, conjunctivitis and otitis media. Current polysaccharide vaccines are strictly serotype-specific and also drive the emergence of non-vaccine serotype strains. In this study, we used microarray analysis to compare gene expression patterns of either serotype 4 or serotype 6A pneumococci in the nasopharynx and blood of mice, as a model to identify genes involved in invasion of blood in the context of occult bacteremia in humans. In this manner, we identified 26 genes that were significantly up-regulated in the nasopharynx and 36 genes that were significantly up-regulated in the blood that were common to both strains. Gene Ontology classification revealed that transporter and DNA binding (transcription factor) activities constitute the significantly different molecular functional categories for genes up-regulated in the nasopharynx and blood. Targeted mutagenesis of selected genes from both niches and subsequent virulence and pathogenesis studies identified the manganese-dependent superoxide dismutase (SodA) as most likely to be essential for colonization, and the cell wall-associated serine protease (PrtA) as important for invasion of blood. This work extends our previous analyses and suggests that both PrtA and SodA warrant examination in future studies aimed at prevention and/or control of pneumococcal disease.

No MeSH data available.


Related in: MedlinePlus

Survival times for mice after i.n. challenge with WCH43 and isogenic mutant derivatives.Groups of 12 CD1 male mice were challenged i.n. with approx. 1 × 107 CFU of the indicated strains. Survival curves were compared using log-rank [Mantel-Cox] and Gehan-Breslow-Wilcoxon) tests. (* P<0.05; ** P<0.01).
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pone.0141816.g003: Survival times for mice after i.n. challenge with WCH43 and isogenic mutant derivatives.Groups of 12 CD1 male mice were challenged i.n. with approx. 1 × 107 CFU of the indicated strains. Survival curves were compared using log-rank [Mantel-Cox] and Gehan-Breslow-Wilcoxon) tests. (* P<0.05; ** P<0.01).

Mentions: After intranasal challenge of mice, the ΔprtA, ΔsodA mutants and, to a lesser extent, the ΔvanZ mutant of WCH43 were significantly attenuated for virulence, while the ΔulaA mutant was essentially as virulent as the wild type (Fig 3). To assess the involvement of prtA, sodA and vanZ in colonization or blood invasion, we challenged groups of mice i.n. with approx. 3 × 106 CFU of either mutant or the isogenic wild-type WCH16 or WCH43 strain and harvested bacteria from the nasopharynx, lungs and blood at 48 h post-infection. For WCH43, we found that only the ΔsodA mutant was significantly attenuated for colonization of the nasopharynx (Fig 4A), while the numbers of ΔprtA and ΔsodA mutants were significantly lower in lungs (Fig 4B) and blood (Fig 4C) compared to wild type. However, while the numbers of the ΔvanZ mutant bacteria were generally lower in blood than those for the wild type, this did not reach statistical significance. To verify these results, we repeated the pathogenesis experiment using WCH16 and its isogenic ΔprtA, ΔsodA and ΔvanZ mutants. As observed for WCH43, the ΔsodA mutant was also significantly attenuated for colonization of the nasopharynx (Fig 4D), However, the differences in pathogenesis of the mutants in WCH16 in lungs (Fig 4E) and blood (Fig 4F) did not reach statistical significance, consistent with our previous observations that WCH16 displays minimal lung and blood involvement during pathogenesis [39, 40].


Characterization of Pneumococcal Genes Involved in Bloodstream Invasion in a Mouse Model.

Mahdi LK, Van der Hoek MB, Ebrahimie E, Paton JC, Ogunniyi AD - PLoS ONE (2015)

Survival times for mice after i.n. challenge with WCH43 and isogenic mutant derivatives.Groups of 12 CD1 male mice were challenged i.n. with approx. 1 × 107 CFU of the indicated strains. Survival curves were compared using log-rank [Mantel-Cox] and Gehan-Breslow-Wilcoxon) tests. (* P<0.05; ** P<0.01).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4634996&req=5

pone.0141816.g003: Survival times for mice after i.n. challenge with WCH43 and isogenic mutant derivatives.Groups of 12 CD1 male mice were challenged i.n. with approx. 1 × 107 CFU of the indicated strains. Survival curves were compared using log-rank [Mantel-Cox] and Gehan-Breslow-Wilcoxon) tests. (* P<0.05; ** P<0.01).
Mentions: After intranasal challenge of mice, the ΔprtA, ΔsodA mutants and, to a lesser extent, the ΔvanZ mutant of WCH43 were significantly attenuated for virulence, while the ΔulaA mutant was essentially as virulent as the wild type (Fig 3). To assess the involvement of prtA, sodA and vanZ in colonization or blood invasion, we challenged groups of mice i.n. with approx. 3 × 106 CFU of either mutant or the isogenic wild-type WCH16 or WCH43 strain and harvested bacteria from the nasopharynx, lungs and blood at 48 h post-infection. For WCH43, we found that only the ΔsodA mutant was significantly attenuated for colonization of the nasopharynx (Fig 4A), while the numbers of ΔprtA and ΔsodA mutants were significantly lower in lungs (Fig 4B) and blood (Fig 4C) compared to wild type. However, while the numbers of the ΔvanZ mutant bacteria were generally lower in blood than those for the wild type, this did not reach statistical significance. To verify these results, we repeated the pathogenesis experiment using WCH16 and its isogenic ΔprtA, ΔsodA and ΔvanZ mutants. As observed for WCH43, the ΔsodA mutant was also significantly attenuated for colonization of the nasopharynx (Fig 4D), However, the differences in pathogenesis of the mutants in WCH16 in lungs (Fig 4E) and blood (Fig 4F) did not reach statistical significance, consistent with our previous observations that WCH16 displays minimal lung and blood involvement during pathogenesis [39, 40].

Bottom Line: In this manner, we identified 26 genes that were significantly up-regulated in the nasopharynx and 36 genes that were significantly up-regulated in the blood that were common to both strains.Gene Ontology classification revealed that transporter and DNA binding (transcription factor) activities constitute the significantly different molecular functional categories for genes up-regulated in the nasopharynx and blood.Targeted mutagenesis of selected genes from both niches and subsequent virulence and pathogenesis studies identified the manganese-dependent superoxide dismutase (SodA) as most likely to be essential for colonization, and the cell wall-associated serine protease (PrtA) as important for invasion of blood.

View Article: PubMed Central - PubMed

Affiliation: Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia.

ABSTRACT
Streptococcus pneumoniae (the pneumococcus) continues to account for significant morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteremia and meningitis, as well as less serious infections such as sinusitis, conjunctivitis and otitis media. Current polysaccharide vaccines are strictly serotype-specific and also drive the emergence of non-vaccine serotype strains. In this study, we used microarray analysis to compare gene expression patterns of either serotype 4 or serotype 6A pneumococci in the nasopharynx and blood of mice, as a model to identify genes involved in invasion of blood in the context of occult bacteremia in humans. In this manner, we identified 26 genes that were significantly up-regulated in the nasopharynx and 36 genes that were significantly up-regulated in the blood that were common to both strains. Gene Ontology classification revealed that transporter and DNA binding (transcription factor) activities constitute the significantly different molecular functional categories for genes up-regulated in the nasopharynx and blood. Targeted mutagenesis of selected genes from both niches and subsequent virulence and pathogenesis studies identified the manganese-dependent superoxide dismutase (SodA) as most likely to be essential for colonization, and the cell wall-associated serine protease (PrtA) as important for invasion of blood. This work extends our previous analyses and suggests that both PrtA and SodA warrant examination in future studies aimed at prevention and/or control of pneumococcal disease.

No MeSH data available.


Related in: MedlinePlus