Unknown,Transcriptomics,Genomics,Proteomics

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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. Expression of S. aureus O46 from subclinical mastitis and O11 from a lethal gangrenous mastitis were compared at two different times

ORGANISM(S): Staphylococcus aureus

SUBMITTER: FRANCOIS Patrice

PROVIDER: E-GEOD-25084 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Staphylococcus aureus is a major pathogen of humans and animals and rapidly emerging antibiotic-resistant strains have further increased the severity of this health issue. Host genetics influence susceptibility to S. aureus infections, and genes determining infection outcome should be identified to analyze immune-based therapies as an alternative to antibiotics. Here, we used outbred animals from a divergent selection on susceptibility towards Staphylococcus infection to explore host immunogenetics. Methodology/Principal Findings: We investigated how dendritic cells respond to heat-inactivated S. aureus and whether dendritic cells from animals with different degree of susceptibility have distinct gene expression profiles. We measured expression levels of 15K probes from in vitro S. aureus-stimulated bone marrow-derived dendritic cells at three different time points (0, 3 and 8 hours) by using Agilent microarrays. Furthermore, a selected number of genes were confirmed by RT-qPCR. Gene signatures of stimulated DCs were obtained and genes involved in inflammatory process and T helper cell polarization were highly up regulated upon stimulation. Moreover, a set of 204 genes were statistically different between susceptible and resistant animals, and grouped them according to their predisposition to staphylococcal infection. Interestingly, a role of classical pathway of Complement and early regulation of inflammation is observed in the resistant line through over expression of C1q and Ido1 genes respectively. On the opposite, over expression of genes in the IL1R pathway in the susceptible animals was noticed. Furthermore, leucocyte extravasation pathway was also found dominant in the susceptible line. Conclusion/Significance: we successfully obtained Staphylococcus aureus associated gene expression of ovine BM-DC in 8 hour kinetics experiment. Distinct transcriptional profiles of dendritic cells obtained from resistant and susceptible lines may explain susceptibility towards S. aureus infections in a broad context. Keywords: Staphylococcus aureus, dendritic cells, mammalian, transcriptome, immunity, mastitis 44 sample records; two-colour dye-swap experimental design

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Molecular bases of virulence variability in Staphylococcus aureus mastitis isolates

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