Evaluation of a latex agglutination test (MRSA-Screen) for detection of oxacillin resistance in coagulase-negative staphylococci

The MRSA-Screen (Denka-Seiken, Tokyo, Japan) latex agglutination test was e valuated for its ability to detect PBP 2a from 200 clinical isolates of coa gulase-negative staphylococci (CONS; 84 mecA-positive strains and 116 mecA- negative strains) consisting of 108 Staphylococcus epidermidis, 37 S. sapro phyticus, 15 S. haemolyticus, 11 S. hominis, 10 S. capitis, 10 S. warneri, and 3 S. lugdunensis species as well as 6 other species of CONS. The assay was compared with susceptibility testing with an agar screen plate with oxa cillin at 6 mug/ml (OXA6), by oxacillin disk diffusion (DD), by broth micro dilution (BMDIL), by the E test, and with Vitek GPS-SV and Vitek GPS-107 su sceptibility cards. PCR for the detection of the mecA gene was used as the "gold standard." The sensitivities and specificities for the methods evalua ted were as follows: MRSA-Screen, 100 and 100%, respectively; OXA6, 100 and 99%, respectively; DD, 98 and 62%, respectively; BMDIL, 100 and 60%, respe ctively; E test, 100 and 51%, respectively; Vitek GPS-SV susceptibility car d, 98 and 87%, respectively; and Vitek GPS-107 susceptibility card, 100 and 61%, respectively. The MRSA-Screen test accurately and rapidly detected ox acillin resistance in CONS.