Molecular Basis of Virulence in Staphylococcus aureus Mastitis

INRA, UMR1253, Science et Technologie du Lait et de l'Œuf, Rennes, France.
PLoS ONE (Impact Factor: 3.23). 11/2011; 6(11):e27354. DOI: 10.1371/journal.pone.0027354
Source: PubMed


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. 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 reproducibly induce severe (strain O11) and milder (strain O46) mastitis in ewes. 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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    • "Similarly, our findings also differ from the results of more recent DNA microarray or PCR studies that revealed very similar virulence gene expression profiles in isolates with the same sequence type (Jamrozy et al. 2012; Shambat et al. 2012). Our results do agree with those of Munsky et al. (2012) and Le Maréchal et al. (2011) who found variable gene expression in identical environments even when the cells were genetically identical. One explanation of this variability is the possible accumulation of truncations and other nucleotide differences in certain genes. "
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    ABSTRACT: Several studies have shown that protein expression patterns vary in unrelated bacterial strains due to genomic plasticity and gene regulation, resulting in enhanced heterogeneity in the infection potential. However, exoprotein expression patterns of closely related clonal strains have not been well characterized. Here, we used medium-range (pH 4–7) immobilized pH gradient–two-dimensional gel electrophoresis to investigate the exoproteome from closely related Staphylococcus aureus clonal isolates. Interestingly, we found that, under identical in vitro experimental conditions, a number of protein spots were uniquely present in samples from each clonal isolate irregardless of the similarity of the genotype and the same virulence gene profile. Only a few abundant invariant proteins were found among identical genotypic isolates. Our results clearly shown that heterogeneity in the exoproteome was present even among clonally related strains. We suggest that this heterogeneity may contribute to the degree of virulence even within one clonal genotype. The heterogeneity in the exoproteome of closely related S. aureus strains observed in the current study postulates that pre-existing antibodies are not very protective during recurrent infection with the same strain. Therefore, our findings underscore the importance of taking all clonally related strains into account during proteome analyses.
    Annals of Microbiology 09/2015; 65(3). DOI:10.1007/s13213-015-1064-7 · 0.99 Impact Factor
    • "We recently identified an ET-like protein in S. aureus O46, a strain associated to mild ewe mastitis [13] [14]. It showed high similarity with previously described S. aureus ETD in its amino acid primary sequence, including the presence of the typical catalytic site found in the other ET proteins described so far, and was thus named EDT-like. "
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    Biochemical and Biophysical Research Communications 08/2015; 467(1). DOI:10.1016/j.bbrc.2015.08.083 · 2.30 Impact Factor
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    • "Studies around the world have reported a diversity of S. aureus genotypes associated with IMI (Akineden et al., 2001; Buzzola et al., 2001; Larsen et al., 2002; Zadoks et al., 2002; van Leeuwen et al., 2005; Haveri et al., 2008; Vautor et al., 2009; Wang et al., 2009; Hata et al., 2010; Wolf et al., 2011; Klein et al., 2012; Mitra et al., 2013). Also, S. aureus strains involved in bovine IMI were shown to present a variety of genotypes and phenotypes that include disease severity and IMI persistence and the capacity to produce specific toxins, biofilm, or both (Matsunaga et al., 1993; Fitzgerald et al., 2000; Cucarella et al., 2004; Zschöck et al., 2005; Zecconi et al., 2006; Haveri et al., 2007; Kalorey et al., 2007; Le Maréchal et al., 2011; Oliveira et al., 2011; Ote et al., 2011; Bardiau et al., 2014). Additional information is needed for a complete understanding of the disease and more specifically for identifying the bacterial factors responsible for the persistence of IMI. "
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    Journal of Dairy Science 10/2014; 98(1). DOI:10.3168/jds.2014-8044 · 2.57 Impact Factor
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