Rapid detection of methicillin resistance in Staphylococcus aureus isolates by the MRSA-Screen latex agglutination test

The slide agglutination test MRSA-Screen (Denka Seiken Co., Niigata, Japan) was compared with the mecA PCR ("gold standard") for the detection of meth icillin resistance in Staphylococcus aureus. The MRSA-Screen test detected the penicillin-binding protein 2a (PBP2a) antigen in 87 of 90 genetically d iverse methicillin-resistant S. aureus (MRSA) stock culture strains, leadin g to a sensitivity of 97%. The three discrepant MRSA strains displayed posi tive results only after induction of the mecA gene by exposure to methicill in. Both mecA PCR and MRSA-Screen displayed negative results among the meth icillin-susceptible S. aureus strains (n = 106), as well as for Micrococcus spp. (n = 10), members of the family Enterobacteriaceae (n = 10), Streptoc occus pneumoniae (n = 10), and Enterococcus spp. (n = 10) (specificity = 10 0%). Producing the same PBP2a antigen, all 10 methicillin-resistant Staphyl ococcus epidermidis strains score positived in both the latex test and the mecA PCR. Consequently, the MRSA-Screen test should be applied only after i dentification of the MRSA strain to the species level to rule out coagulase -negative staphylococci. In conclusion, due to excellent specificity and se nsitivity the MRSA-Screen latex test has the potential to be successfully u sed for routine applications in the microbiology laboratory.