The Combined Oxacillin Resistance and Coagulase (CORC) test for rapid identification and prediction of oxacillin resistance in Staphylococcus species directly from blood culture.
Abstract
We describe the Combined Oxacillin Resistance and Coagulase (CORC) protocol for rapid identification and determination of oxacillin-susceptibility in Staphylococcus spp from blood culture. 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 81.5-99.8) and 100% (95%CI 75.9-100) respectively, N=47) and for prediction of oxacillin resistance in Staphylococcus aureus directly from patient blood cultures (100% (95%CI 59.8-100) and 100% (95%CI 82.2-100) respectively, N=31) within 5 hours of blood culture positivity.
