Molecular characterization of methicillin-resistant Staphylococcus epidermidis strains from bacteraemic patients

Abstract

In order to study the clonality of clinical methicillin-resistant Staphylococcus epidermidis (MRSE) strains and their staphylococcal cassette chromosome mec (SCC mec) elements, 60 isolates of MRSE from bacteraemic patients in three units of the Helsinki University Hospital, Finland were selected, covering the periods 1990-1993 and 1997-1998. The MRSE strains were analysed by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing and SCC mec typing. Eleven PFGE types (FIN-SE-1-11) with sequence type ST2 (clonal complex 2; CC2) were identified. The previously established methicillin-resistant Staphylococcus aureus SCC mec criteria were applied to name the MRSE SCC mec complexes, and it was found that 7% of the isolates carried SCC mec type IA (ccrA1, class B), whereas the majority (93%;) yielded six non-typeable SCC mec PCR patterns (P1-P6). Within each SCC mec PCR pattern, two ccr recombinase genes (ccrA2 and ccrA3) and two mec gene complexes (class A and class B) were detected. In addition, the ccrC gene was associated with three of the six patterns. In conclusion, the MRSE strains were genetically related to each other (ST2) but their SCC mec complexes were unique combinations of elements previously recognized among SCC mec types III and IV. © 2008 The Authors Journal compilation © 2008 European Society of Clinical Microbiology and Infectious Diseases.