BACKGROUND: Increasing rates of methicillin-resistant
Staphylococcus aureus(MRSA) infections on a global scale is a major health concern. In Canada, there are 10 known epidemic types of MRSA as determined by pulsed-field gel electrophoresis (PFGE). Despite the excellent discriminatory power of PFGE, there are several disadvantages of using this technique, such as high degree of labour intensity and the inability to easily develop an MRSA typing database due to the subjective interpretation of results.
OBJECTIVES: The purpose of the present study was to determine whether
spatyping, an established DNA sequence-based typing method, could be used as an alternative to PFGE for the typing of Canadian MRSA (CMRSA) epidemic isolates.
spatypes were determined for 1488 CMRSA isolates, and the method was analyzed for its ability to identify and cluster CMRSA1-10 strains. Minimal spanning tree analysis of 1452 spatypes revealed individual clonal clusters for PFGE epidemic types CMRSA1, 2, 7 and 8, but spatyping could not distinguish CMRSA5 from CMRSA9 and CMRSA10, and CMRSA3 from CMRSA4 and CMRSA6. However, specific spatypes were generally associated with only one PFGE epidemic type. Based on these results, a spatyping guideline for CMRSA isolates was developed and tested using the first 300 MRSA isolates received in 2007 through the Canadian Nosocomial Infection Surveillance Program.
CONCLUSIONS: The high concordance of
spatypes with PFGE epidemic types using this guideline demonstrated the feasibility of spatyping as a more rapid and less technically demanding alternative typing method for MRSA in Canada.