The virulence gene expression pattern of different clinical isolates of <I>Staphylococcus aureus</I> is more heterogeneous than expected from the genomic situation
| Authors | |
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| Year of publication | 2008 |
| Type | Article in Proceedings |
| Conference | 13th International Symposium on Staphylococci and Staphylococcal Infections |
| MU Faculty or unit | |
| Citation | |
| Web | http://www.isssi2008.com/ |
| Field | Genetics and molecular biology |
| Keywords | Staphylococcus aureus; extracellular proteome; proteomics analysis; virulence factors |
| Description | The pathogenicity of Staphylococcus aureus is determined by its ability to express several virulence factors. Thus far the virulence potential of S. aureus isolates has been described by the virulence gene repertoire which is in part considerably variable among the different isolates. The present study focuses on the expression of virulence related genes by analysing the extracellular proteome of 25 clinical isolates of different origins (e.g. wound infection, arthritis or sepsis). For genetic and epidemiological studies, we utilised the well established Pulse-Field-Gel-Electrophoresis (PFGE) and Multi-Locus-Sequence-Typing (MLST) techniques. Moreover, the agr type and the presence of some virulence genes (e.g. superantigens, pvl, etd, eta) was determined by using Multiplex PCR. Accordingly, the isolates can be grouped into 11 different sequence types. Three new sequence types were detected: ST869, ST870, and ST903. Analysing the agr type, 6 isolates express agr1, 13 agr2, 3 agr3 and none of the isolates express agr4. Additionally, we analysed the prophage content of these strains by using a multiplex PCR assay as well. Altogether we identified 11 different prophages. While most of the isolates contain three prophages, in two isolates non prophage could be detected. Comparison of the extracellular protein patterns revealed a very high heterogeneity between the clinical isolates. However, this is not only due to the diversity of the virulence gene repertoire but also to variations in the expression rate of the respective genes which makes the anyhow complex virulence gene repertoire of the different isolates even more complex and might explain their different virulence potential. At least 107 of the identified proteins showed signal sequences typical for Sec-translocated proteins. Sixteen extracellular proteins were found in at least 80% of the isolates. Thereof seven proteins (Aly, Hla, IsaA, LytM, Nuc, SA0620, SA2097) could be detected in all strains. Although these proteins are present in at least 80% of the strains they differed significantly in amount. In contrast, 31 proteins seem to be unique for one or two strains. The functions of most of these proteins are not always clear and have to be elucidated. |
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