Population dynamics among methicillin-resistant Staphylococcus aureus isolates in Germany during a 6-year period

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) originated from the health care setting but is now emerging in communities without health care contact (CA-MRSA) or in livestock (LA-MRSA). The impact on the whole MRSA population was assessed in a German prospective multicenter study. Thirty-three laboratories consecutively collected up to 50 MRSA isolates from infection or carriage during two sampling periods in 2004 to 2005 and 2010 to 2011. Patient-related data were collected using a standardized questionnaire. Methicillin resistance was confirmed by the detection of mecA or its homologue mecA(LGA251). The spa type and major virulence factors were analyzed for each isolate. In total, 1,604 (2004 to 2005) and 1,603 (2010 to 2011) MRSA isolates were analyzed; one isolate from each sampling period harbored mecA(LGA251). LA-MRSA increased significantly (odds ratio [OR] = 22.67, 95% confidence interval [CI] = 8.51 to 85.49, P < 0.0005) and spread over Germany, originating from northwestern regions. Panton-Valentine leukocidin-positive CA-MRSA rose significantly, particularly in southern Germany, but the proportion in 2010 to 2011 remained low (2.7%, OR = 2.80, 95% CI = 1.54 to 5.34, P < 0.0005). The emerging MRSA clones changed the MRSA population in Germany during a 6-year period significantly. The ongoing epidemiological shift and changes of MRSA sources create a need for revision of guidelines for MRSA infection control and treatment.

Fig 1

Distribution of the two most prevalent spa types of methicillin-resistant Staphylococcus aureus in Germany. Pie charts show the average prevalence in each federal state.

Fig 2

Distribution and spread of livestock-associated methicillin-resistant Staphylococcus aureus in Germany in 2004 to 2005 and 2010 to 2011. The numbers indicate the prevalence (%) of LA-MRSA isolates in the respective study centers (green, 1%; yellow, 2 to 5%; orange, 6 to 10%; red, >10%). Asterisks indicate that only one study center reported from the region.

Fig 3

Distribution and spread of PVL-positive methicillin-resistant Staphylococcus aureus in Germany in 2004 to 2005 and 2010 to 2011. The numbers indicate the proportions (%) of PVL-positive MRSA isolates in the respective study centers. Colors indicate detection of ST8 (red), ST80 (blue), ST8 and ST80 (violet), and non-ST8/non-ST80 (white).