Molecular characterisation of meticillin-resistant and -susceptible Staphylococcus aureus from global clinical trials

Abstract number: P1427

Goering R.V., Shawar R.M., Scangarella N.E., O'Hara F.P., Madsen H., West J., Dalessandro M., Breton J., Becker J.A., Miller L., Halsey W., Thomas E., Twynholm M., Payne D.

Objectives: To better understand the global epidemiology of Staphylococcus aureus we genotyped meticillin-resistant (MRSA) and -susceptible (MSSA) isolates recovered in 2004–5 from patients with uncomplicated skin infections in 10 countries during five Phase III clinical trials of retapamulin, a new topical antibiotic agent.

Methods:S. aureus isolates were tested for the presence of the Panton-Valentine leukocidin (PVL) genes. All 105 MRSA were analysed to determine the SCCmec type. All MRSA isolates, 118 PVL-positive MSSA, plus a representative subset of 69 PVL-negative MSSA were analysed by pulsed-field gel electrophoresis, and multilocus sequence typing (MLST).

Results: MRSA isolates were recovered mainly from the U.S. (60, 57%), India (27, 26%), Costa Rica (6, 6%), Germany (5, 5%), with the remainder (7, 6%) from South Africa, Russian Federation, France, and Peru. The most common MRSA strain (46, 44%), recovered exclusively in the U.S., was of the community-associated (CA) PVL-positive, ST8, USA300 type. Another four PVL-negative USA300 variants were recovered in Costa Rica and India. No pulsed field type USA300–0114 MRSA were found outside the U.S. Interestingly, a total of 10 PVL-positive and -negative USA300 isolates were found within the MSSA population from the U.S., South Africa, Peru, and Poland. USA800 was the second most common MRSA strain (11, 10%), primarily found in the U.S. and Costa Rica. PVL-positive MSSA isolates were from recovered South Africa (55, 47%), India (34, 29%), Russian Federation (12, 10%), U.S. (9, 8%), and Germany (6, 5%), with one isolate each from Canada and Peru. The most common PVL-positive MSSA strain was USA1200, primarily found in South Africa and the Russian Federation. This was followed by EMRSA15-related strains found only in South Africa and India. There was no predominant strain within the PVL-negative MSSA group with 29% of isolates exhibiting unknown types.

Conclusions: While results of this study are necessarily limited by the isolate numbers from countries in which patients were enrolled, the CA-MRSA strain USA300 was clearly associated with U.S. testing centres while no isolates of the major European ST80 CA-MRSA clone were recovered. In a number of instances genetic backgrounds associated with MRSA outbreaks were found in MSSA. The results underscore the importance of MRSA and MSSA surveillance to enhance understanding of the global spread and persistence of different S. aureus populations.

Session Details

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