Evaluation of a commercial MRSA assay when multiple MRSA strains are causing epidemics.

Rapid and reliable diagnostic methods are needed to control methicillin-resistant Staphylococcus aureus (MRSA) transmission. We studied the BD GeneOhm MRSA Assay which is based on one specific amplification product at the junction of the right extremity sequence of the staphylococcal cassette chromosome mec (SCCmec) and the chromosomal sequence of orfX of S. aureus. The test was applied on 95 clinical isolates in Finland: 83% were positive. The isolates giving negative results represented several pulsed-field gel electrophoresis (PFGE) types and harboured SCCmec types IV, V, VI or were new types with different combinations of ccr genes.