Evaluation of the BinaxNOW Staphylococcus aureus test for rapid identification of Gram-positive cocci from VersaTREK blood culture bottles.

The ability of the rapid BinaxNOW Staphylococcus aureus (BNSA) immunochromatographic test (Alere Scarborough, Inc., ME) to accurately differentiate S. aureus from coagulase-negative staphylococci (CoNS) and other Gram-positive cocci (GPC) directly from VersaTREK blood culture bottles was evaluated. A total of 319 positive patient blood culture bottles with GPC seen in clusters with Gram staining were tested using the BNSA test and a direct tube coagulase test (DTCT). The BNSA test was accurate for the detection and differentiation of S. aureus from CoNS and other GPC within 30 min from the time of blood culture positivity and demonstrated a test sensitivity and specificity of 95.8% and 99.6%, respectively. BNSA test results were faxed to the antimicrobial stewardship pharmacist by noon each day in order to evaluate empirical antimicrobial therapy and facilitate more rapid changes or modifications if necessary. Same-day reporting of BNSA test results in conjunction with an antimicrobial stewardship program was more impactful in improving treatment for inpatients with documented S. aureus bacteremia than in reducing empirical vancomycin use in inpatients with CoNS during the first 24 h following reporting.