Abstract

The combined oxacillin resistance and coagulase (CORC) protocol for rapid identification and determination of oxacillin-susceptibility in Staphylococcus spp from blood culture is described. It incorporates a modified direct tube coagulase test (TCT) and a novel 4-hour multiplication-induction step, which increases the expression of staphylococcal PBP2a if present, facilitating detection by a commercial PBP2a latex agglutination kit. The protocol shows excellent sensitivity and specificity for determination of coagulase-positivity in staphylococci from patient blood cultures (96.8% (95% CI 81.5 to 99.8) and 100% (95% CI 75.9 to 100), respectively, n = 47), and for prediction of oxacillin resistance in S aureus directly from patient blood cultures (100% (95% CI 59.8 to 100) and 100% (95% CI 82.2 to 100), respectively (100% accuracy), n = 31) within 5 hours of blood culture positivity.