PCR-RFLP analysis of the coagulase gene of Staphylococcus aureus: application to the differentiation of epidemic and sporadic methicillin-resistant strains

Preventing cross-infection with epidemic strains of methicillin-resistant S taphylococcus aureus (MRSA) requires effective control measures. These call for simple, rapid, discriminatory and reproducible methods for typing this pathogen. In this study 140 isolates/strains from 105 hospitals in England and Wales, representing 72 diverse phage types, were analysed by bacteriophage typing and PCR coagulase (con) gene restriction fragment length polymorphism (RFL P). Isolates gave a con gene PCR product that was either 660 base pairs (bp ), 603 bp or 547 bp in size. The PCR products m-ere digested with Alu I and Cfo I, and the fragments separated by gel electrophoresis. Eight con gene RFLP patterns, numbered 1 to 8, were observed. Pattern 3 was most common (N =25 isolates), followed by patterns 2 and 5 (18 isolates each), pattern 1 ( 14 isolates), pattern 4 (11 isolates), pattern 7 (10 isolates), pattern 8 ( eight isolates) and pattern 6 (six isolates). Isolates of the same phage ty pe often gave different con gene RFLP patterns, and the patterns within the epidemic types EMRSA-03, EMRSA-15 and EMRSA-16 were heterogeneous. Thus, r epresentatives of EMRSA-03 were subtyped to coa RFLP patterns 1 and 2, thos e of EMRSA-05 to coa RFLP patterns 1, 2, 7 and 8, and those for MRSA-16 to coa RFLP patterns 2, 3, 4, 5 and 6. The range of patterns within single pha ge types of S. aureus could help to discriminate between isolates/strains, and in a hierarchical approach con gene RFLP could occupy an intermediate p osition between phage typing and pulsed-field gel electrophoresis (PFGE).