Abstract
Rapid and reliable detection of methicillin-resistant Staphylococcus aureus (MRSA) carriers is crucial for control of MRSA nosocomial transmission. We aimed to evaluate the performance of the GeneXpert real-time PCR system using the Xpert MRSA assay on a collection of 40 representative Belgian MRSA strains and for MRSA screening of geriatric inpatients. Double nasal swabs were used: the first swab for the Xpert MRSA assay and the second for culture onto chromogenic selective medium and enrichment broth. All but 1 of the 40 collection strains were recognized as MRSA by the Xpert MRSA assay. Nares swabs were prospectively collected from 246 inpatients including 25 nasal MRSA carriers. Compared with enriched cultures, the sensitivity, the specificity, and the positive and negative predictive values of the Xpert MRSA assay were 69.2%, 97.7%, 78.3%, and 96.3% respectively. The 7 evaluable false-negative results according to the assay were due to its possible lack of sensitivity (n = 3) and to the occurrence of a Belgian MRSA clone carrying a particular staphylococcal chromosomal cassette mec (SCCmec) type IV variant (n = 4) not targeted by the current Xpert MRSA assay. Because of the evolution of SCCmec in MRSA, new primers should be designed and further studies are warranted to ensure continuous monitoring of this assay.
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Acknowledgements
We thank the participating patients, the infection control and nursing staff (Serge Dupont, Laurent Tonnoir) and the clinical staff of the geriatric unit at UCL Mont-Godinne hospital for providing duplicate specimens. We thank Mrs. Kathleen Stam and Mr. Luc De Bock, Lucron Belgium, and Cepheid for providing the GeneXpert machine for the duration of the evaluation and for providing the Xpert MRSA kits at an evaluation price.
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Laurent, C., Bogaerts, P., Schoevaerdts, D. et al. Evaluation of the Xpert MRSA assay for rapid detection of methicillin-resistant Staphylococcus aureus from nares swabs of geriatric hospitalized patients and failure to detect a specific SCCmec type IV variant. Eur J Clin Microbiol Infect Dis 29, 995–1002 (2010). https://doi.org/10.1007/s10096-010-0958-3
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DOI: https://doi.org/10.1007/s10096-010-0958-3