In the centre of an epidemic: Fifteen years of LA-MRSA CC398 at the University Hospital Münster

- Report on a 15-years-period of LA-MRSA CC398 epidemic.
- Reporting of the first or at least one of the first human-associated LA-MRSA CC398 isolates reported in Europe.
- Analysis of the development of the intra-lineage diversity of the LA-MRSA CC398 reaching a total of 45 different spa types.

Ten years after initial publications on livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in 2005, we report on the course of the LA-MRSA CC398 epidemic among patients of the University Hospital Münster. This tertiary care facility is located in the Dutch-German border region (EUREGIO), which is characterized by a high density of livestock production and is hence a hotspot for the occurrence of LA-MRSA CC398. Taking advantage of the unique opportunity to track the emergence and spread of MRSA CC398 among humans from the very beginning of the epidemic until today, a total of 6555 non-duplicate MRSA isolates from all screenings and clinical specimens cultivated within the period from 2000 to 2014 were included in the analysis. Retrospectively, the first MRSA CC398 isolate (spa type t034) was obtained from a screening specimen of a patient in 2000, which represents one of the first human-associated LA-MRSA CC398 isolates reported in Europe. After sporadic detections between 2000 and 2004, this clonal lineage accounted for 9.6% of all local MRSA in 2005; a proportion which increased to 35% in 2013 and became stable since then. Considering the period from 2000 to 2014, the group of MRSA CC398 isolates comprised a total of 45 different spa types among which t011 (48.3%), t034 (39.3%) and t108 (3.5%) were predominant and so far unreported types were found. Overall, LA-MRSA CC398 emerged rapidly during the past decade, developed enormous sublineage diversity and contributed substantially to the total burden of MRSA colonization and infection at the hospital.