Molecular basis of virulence in Staphylococcus aureus ovine mastitis
2011
Le Maréchal, Caroline | Seyffert, Nubia | Jardin, Julien | Hernandez, D | Jan¨, Gwénaël, | Azevedo, V. | François, P. | Schrenzel, J. | Even, Sergine | Berkova, Nadejda | Thiéry, R. | Fitzgerald, J.R. | Lortal, Sylvie | Le Loir, Yves
S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis and is dependent on host as well as bacterial factors. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection. We employed genomic, transcriptomic and proteomic approaches to comprehensively compare two clonally related S. aureus strains that were responsible for severe (strain O11) and milder (strain O46) mastitis in ewes, respectively. Variation in the content of mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production was observed. In particular, O11 produced relatively high levels of exoproteins, including toxins and proteases known to be important in virulence. a characteristic we observed in other S. aureus strains isolated from clinical mastitis cases. Our data are consistent with a dose-dependant role of some staphylococcal factors in the hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins and iron acquisition pathways constitute good targets for further research to define the underlying mechanisms of mastitis severity.
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