Molecular bases of virulence variability in Staphylococcus aureus mastitis isolates

ABSTRACT: Background: S. aureus is one of the main pathogen involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable and ranges from subclinical to gangrenous mastitis. Such variability implies host as well as staphylococcal factors. This work is an in-depth characterization of S. aureus mastitis isolates to identify factors involved in mastitis severity. Methods and findings: We combined three “omic” approaches to comprehensively compare two clonally related S. aureus strains that were isolated from and shown to reproducibly induce severe (strain O11) and milder (strain O46) mastitis in ewes. The genomes of O11 and O46 were sequenced (Illumina technology) to determine their respective gene content and comparative transcriptomic and proteomic analyses were carried out on both strains grown in conditions mimicking mastitis context. High differences were highlighted in mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production. In particular, O11 overproduced exoproteins, including toxins and proteases when compared to O46. This was confirmed in 4 other S. aureus strains isolated from subclinical or clinical mastitis cases. Dose-dependant production of some staphylococcal factors seem to play a role in hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins or strain ability to deal with iron starvation constitute good targets for further research to better define the underlying mechanisms of mastitis severity. Conclusions: Differences observed in mastitis severity likely result from the ability of the strains to adapt and to express virulence factors in the mastitis context rather than from deep variations in gene content.

ORGANISM(S): Staphylococcus aureus

PROVIDER: GSE25084 | GEO | 2011/11/11

SECONDARY ACCESSION(S): PRJNA134753

REPOSITORIES: GEO