Regional variation and temporal trends of Meticillin-resistant Staphylococcus aureus using the Sentinel Surveillance of Antibiotic Resistance in Switzerland (SEARCH)

Abstract number: P1422

Albrich W.C., Kronenberg A., Mühlemann K.

Objectives: The epidemiology of Meticillin-resistant Staphylococcus aureus (MRSA) shows large geographic variations. Recently, a comprehensive national antibiotic resistance database covering in- and outpatients became available in Switzerland.

Methods: We used a laboratory-based active surveillance system (SEARCH, www.search.ifik.unibe.ch) of in- and outpatients in Switzerland with S. aureus isolated from any source to analyse regional and temporal trends in the epidemiology of MRSA.

Results: The proportion of meticillin-resistance in S. aureus was highest for long-term facilities (26.2%), followed by general hospital wards (7.4%) and Intensive Care Units (5.4%) and lowest in outpatients (3.5%) (p < 0.05 for each comparison). MRSA was more frequent in males than females (RR 1.19; p < 0.001) and increased with older age (p for trend <0.001). Meticillin-resistance tended to increase since 2004 from 6.2% to 6.6% in 2007 (p for trend 0.06) with significant increases over time in the proportion of MRSA within most age groups and for females (from 5.3% in 2004 to 6.2% in 2007; p for trend <0.001) but not for males. The proportion of MRSA among S. aureus from general practitioners and long-term facilities tended to increase since 2004, whereas no change was evident for hospital isolates. Marked geographic variations were observed with highest proportions of MRSA in the South (17.1%), followed by the West of Switzerland (10.4%) and lowest proportions in Central (3.9%) and Eastern Switzerland (3.8%). While there was a significant increase in the East (3.2% in 2004, 4.0% in 2007; p for trend 0.04), elsewhere prevalence remained stable (Central) or showed a non-significant increase (West: 8.9% in 2004, 10.7% in 2007) or decrease (South: 18.1% in 2004, 15.9% in 2007). Cotrimoxazole (3.8%) and tetracycline resistance (7.9%) in MRSA remained low in 2007, while 43%, 66% and 74% were resistant against clindamycin, erythromycin and ciprofloxacin, respectively. Resistance rates of MRSA against clindamycin and ciprofloxacin decreased significantly since 2004. Temporal resistance trends for individual antibiotics varied markedly across regions. There was a trend towards an increase of non-multidrug resistant MRSA since 2004 (p for trend 0.09). The risk of MRSA was slightly higher during the cold season than in warmer months (RR 1.05; p 0.04).

Conclusion: MRSA prevalence remains low in Switzerland but both prevalence and temporal trends differ widely across regions.