Molecular epidemiology of Staphylococcus aureus in asymptomatic carriers
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Microarrays were used to extensively characterise 155 Staphylococcus aureus isolates obtained from asymptomatic carriers from Saxony, Germany, in order to determine clonal complex affiliation, as well as the carriage of clinically relevant genes. Isolates belonged to 20 different clonal complexes (CCs). The most common CC was CC8 (18.71%), followed by CCs 15, 30 and 45. Three isolates (1.94%) were methicillin-resistant S. aureus (MRSA). Beta-lactamase was common (70.97%), but other resistance genes were found only sporadically. Genes encoding superantigens were abundant. The enterotoxin cluster egc was found in 45.81% of isolates. The toxic shock syndrome toxin gene tst was detected in 14.84% of isolates and 17.42% harboured enterotoxin A alleles (sea, sea-N315). Contrarily, Panton-Valentine leukocidin (lukS/F-PV) was rare, being found in only one methicillin-susceptible CC30 isolate. Its low prevalence in asymptomatic carriers might emphasise a pathogenetic significance in patients with skin and soft tissue infections. Most microbial surface components recognising adhesive matrix molecules of the host (MSCRAMMs) genes were nearly ubiquitously present. However, two MSCRAMM genes, cna (collagen adhesion) and sasG (surface protein G), were detected in only some CCs. These data provide an insight into its pathogenesis, especially when compared to isolates from patients with defined clinical conditions. They might also be helpful for the design of a future vaccine.
KeywordsAsymptomatic Carrier Core Genome Toxin Gene Nasal Swab Toxic Shock Syndrome
The authors thank A. Ruppelt, H. Kanig, S. Kolewa, E. Müller, I. Engelmann and J. Sachtschal for their excellent technical assistance, R. Labugger for the helpful remarks, as well as V. Baier and T. Uhlig for developing the software used in the microarray analysis. We acknowledge Prof. E. Jacobs for his support and the Vice-Directorate for Research of the Medical Faculty of Dresden for funding (MeDDrive program 2008).
Ralf Ehricht and Peter Slickers are employees of CLONDIAG.
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