Molecular epidemiology of the nasal colonization by methicillin-susceptible Staphylococcus aureus in Swiss children |
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| Authors: | C. Mégevand A. Gervaix U. Heininger C. Berger C. Aebi B. Vaudaux C. Kind H.-P. Gnehm M. Hitzler G. Renzi J. Schrenzel P. François |
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| Affiliation: | 1. Department of Paediatrics, University of Geneva Hospitals, Geneva, Switzerland;2. University Hospital Basel, Basel, Switzerland;3. University Children’s Hospital Zürich, Zürich, Switzerland;4. Institute for Infectious Diseases, University of Bern, Bern, Switzerland;5. University Children’s Hospital Lausanne, Lausanne, Switzerland;6. Children’s Hospital St-Gallen, St-Gallen, Switzerland;7. Children’s Hospital Aarau, Aarau, Switzerland;8. Children’s Hospital Luzern, Luzern, Switzerland;9. Clinical Microbiology Laboratory, University of Geneva Hospitals, Geneva, Switzerland;10. Genomic Research Laboratory, Service of Infectious Diseases, University of Geneva Hospitals, Geneva, Switzerland |
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| Abstract: | Nasal carriage of Staphylococcus aureus contributes to an increased risk of developing an infection with the same bacterial strain. Genetic regulatory elements and toxin-expressing genes are virulence factors associated with the pathogenic potential of S. aureus. We undertook an extensive molecular characterization of methicillin-susceptible S. aureus (MSSA) carried by children. MSSA were recovered from the nostrils of children. The presence of Panton-Valentine leukocidin (PVL), exfoliatins A and B (exfoA and exfoB), and the toxic-shock staphylococcal toxin (TSST-1) and agr group typing were determined by quantitative PCR. A multiple-locus variable-number of tandem repeat analysis (MLVA) assay was also performed for genotyping. Five hundred and seventy-two strains of MSSA were analysed. Overall, 30% were positive for toxin-expressing genes: 29% contained one toxin and 1.6% two toxins. The most commonly detected toxin gene was tst, which was present in 145 (25%) strains. The TSST-1 gene was significantly associated with the agr group 3 (OR 56.8, 95% CI 32.0–100.8). MLVA analysis revealed a large diversity of genetic content and no clonal relationship was demonstrated among the analysed MSSA strains. Multilocus sequence typing confirmed this observation of diversity and identified ST45 as a frequent colonizer. This broad diversity in MSSA carriage strains suggests a limited selection pressure in our geographical area. |
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| Keywords: | Children molecular epidemiology MSSA nasal colonization Swiss |
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