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Molecular characterisation of meticillin-resistant Staphylococcus aureus nasal isolates from patients with uncomplicated skin infections

Abstract number: P935

Shawar R., Scangarella N., Li G., Twynholm M., Dalessandro M., Breton J., West J., Miller L., O'Hara P., Madsen H., Payne D., Goering R.

Objectives: In order to better understand the clonal composition and epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) from nasal carriage, we molecularly characterised all nasal MRSA isolates recovered in 2004–2005 from patients with uncomplicated skin infections enrolled in Phase III clinical trials of retapamulin, a new topical antibiotic agent.

Methods: Nasal swab samples were obtained from patients with uncomplicated skin infections enrolled in five global phase III clinical trials. All nasal MRSA isolates were examined by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), Staphylococcal cassette chromosome (SCCmec) typing, and were tested for the presence of Panton-Valentine leukocidin (PVL) genes. Nasal MRSA isolates were recovered from patients in 7 different countries (Costa Rica, France, Germany, India, Peru, South Africa, and the United States) but the vast majority were recovered from patients in the United States.

Results: A total of 105 MRSA isolates were recovered from nasal cultures at baseline and/or at follow up visits from 62 patients. Of the 54 baseline MRSA isolates, 23 (42.6%) were determined to be PFGE type USA300, PVL-positive and contained type IV SCCmec and of those 20 were also MLST type 8. Except for one isolate recovered from a patient in Costa Rica, the vast majority (19/20;95%) were recovered from patients in the United States. The remaining 31 MRSA isolates were distributed among 4 other recognised MLST/PFGE genotypes or were not matched to any PFGE types currently in the CDC database. Of the 30 patients who had a nasal MRSA isolate recovered from more than one follow up visit, 19 (63%) had the same PFGE type at each visit.

Conclusions: This study demonstrates that PVL-positive, USA300 MRSA was carried in the anterior nares of patients with uncomplicated skin infections and was found to be the predominant type collected from the baseline nasal samples of patients in the United States. The majority of patients who had MRSA isolated from their anterior nares at two or more visits maintained carriage of the same PFGE type. Both of these findings have significant implications for epidemiologic investigations and for planning future interventional studies.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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