Significant contribution of the pgdA gene to the virulence of Streptococcus suis

Authors

  • Nahuel Fittipaldi,

    1. Groupe de Recherche sur les Maladies Infectieuses du Porc and Centre de Recherche en Infectiologie Porcine, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, QC, J2S 7C6, Canada.
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  • Tsutomu Sekizaki,

    1. Research Team for Bacterial/Parasitic Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
    2. United Graduate School of Veterinary Sciences, Gifu University, 501-1193 Gifu, Japan.
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    • Present address: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.

  • Daisuke Takamatsu,

    1. Research Team for Bacterial/Parasitic Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
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  • María De La Cruz Domínguez-Punaro,

    1. Groupe de Recherche sur les Maladies Infectieuses du Porc and Centre de Recherche en Infectiologie Porcine, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, QC, J2S 7C6, Canada.
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  • Josée Harel,

    1. Groupe de Recherche sur les Maladies Infectieuses du Porc and Centre de Recherche en Infectiologie Porcine, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, QC, J2S 7C6, Canada.
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  • Nhat Khai Bui,

    1. Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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  • Waldemar Vollmer,

    1. Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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  • Marcelo Gottschalk

    Corresponding author
    1. Groupe de Recherche sur les Maladies Infectieuses du Porc and Centre de Recherche en Infectiologie Porcine, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, QC, J2S 7C6, Canada.
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Summary

Streptococcus suis is a major swine pathogen and emerging zoonotic agent. In this study we have determined the muropeptide composition of S. suis peptidoglycan (PG) and found, among other modifications, N-deacetylated compounds. Comparison with an isogenic mutant showed that the product of the pgdA gene is responsible for this specific modification which occurred in very low amounts. Low level of PG N-deacetylation correlated with absence of significant lysozyme resistance when wild-type S. suis was grown in vitro. On the other hand, expression of the pgdA gene was increased upon interaction of the bacterium with neutrophils in vitro as well as in vivo in experimentally inoculated mice, suggesting that S. suis may enhance PG N-deacetylation under these conditions. Evaluation of the ΔpgdA mutant in both the CD1 murine and the porcine models of infection revealed a significant contribution of the pgdA gene to the virulence traits of S. suis. Reflecting a severe impairment in its ability to persist in blood and decreased ability to escape immune clearance mechanisms mediated by neutrophils, the ΔpgdA mutant was highly attenuated in both models. The results of this study suggest that modification of PG by N-deacetylation is an important factor in S. suis virulence.

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