Staphylococcus aureus and methicillin resistance in Switzerland: regional differences and trends from 2004 to 2014

Abstract

BACKGROUND: The global epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) is heterogeneous. The objective of this study was to evaluate MRSA epidemiology in Switzerland over an 11-year period. METHODS: We conducted a retrospective study with time series analysis on S. aureus including MRSA and non-multidrug resistant MRSA (NmMRSA). We used NmMRSA as a marker for community-acquired MRSA. NmMRSA was defined as MRSA susceptible to at least three of the following agents: ciprofloxacin, clindamycin, tetracycline and trimethoprim-sulfamethoxazole. RESULTS: A total of 14 648 MRSA and 115 917 methicillin-susceptible S. aureus (MSSA) isolates were included. Despite an overall decrease of the proportion of MRSA among S. aureus clinical isolates (from 14% in 2004 to 8% in 2014), an increasing trend in NmMRSA was observed. Variations in geographical distribution were noted, with a decrease in the proportion of MRSA in the Italian- and French-speaking regions (from 20–26% in 2004 to 12% in 2014) and low prevalence (3–5%) in the German-speaking region. We noticed an increase in the proportion of MRSA in outpatients (+0.03% per quarter per year) and in the younger population (+0.05% per quarter per year) compared with a decreasing trend in inpatients and the elderly. CONCLUSION: The proportion of MRSA among S. aureus isolates in Switzerland decreased overall from 2004 to 2014. Worrisome increases of NmMRSA were found in younger persons and outpatients.

Keywords

• bacteremia
• MRSA
• MSSA
• Nonmultidrug-MRSA
• times series analysis
• trend