The slide agglutination test MRSA-Screen (Denka Seiken Co., Niigata,
Japan) was compared with the mecA PCR ("gold standard") for the detection
of methicillin resistance in Staphylococcus aureus. The MRSA-Screen test
detected the penicillin-binding protein 2a (PBP2a) antigen in 87 of 90
genetically diverse methicillin-resistant S. aureus (MRSA) stock culture
strains, leading to a sensitivity of 97%. The three discrepant MRSA
strains displayed positive results only after induction of the mecA gene
by exposure to methicillin. Both mecA PCR and MRSA-Screen displayed
negative results among the methicillin-susceptible S. aureus strains (n =
106), as well as for Micrococcus spp. (n = 10), members of the family
Enterobacteriaceae (n = 10), Streptococcus pneumoniae (n = 10), and
Enterococcus spp. (n = 10) (specificity = 100%). Producing the same PBP2a
antigen, all 10 methicillin-resistant Staphylococcus epidermidis strains
score positived in both the latex test and the mecA PCR. Consequently, the
MRSA-Screen test should be applied only after identification of the MRSA
strain to the species level to rule out coagulase-negative staphylococci.
In conclusion, due to excellent specificity and sensitivity the
MRSA-Screen latex test has the potential to be successfully used for
routine applications in the microbiology laboratory