Rapid detection of carbapenemase-producing organisms directly from blood cultures positive for Gram-negative bacilli

INTRODUCTION The rapid detection of carbapenemase-producing organisms (CPOs) directly from blood cultures (BCs) positive for Gram-negative bacilli (GNB) may accelerate the appropriate treatment of at-risk patients. OBJECTIVE To evaluate the performance of two commercial assays in the rapid detection of CPOs directly from BC positive for GNB. METHODS BC positive for GNB were tested for the presence of CPOs with β CARBA® and NG-Test® CARBA 5. A subset of sterile BC samples was seeded with multidrug-resistant (MDR) GNB. Positive BCs from clinical and seeded samples were tested directly with β CARBA and CARBA 5 from BC pellets. RESULTS Sixty-five samples were tested (30 clinical, 35 seeded). β CARBA had a sensitivity, specificity, NPV, and PPV of 100%, 65.7%, 100%, and 71.4%, respectively. CARBA 5 had a sensitivity, specificity, NPV, and PPV of 90.0%, 100%, 92.1%, and 100%. False negatives for CARBA 5 occurred with 1 GES, 1 VIM-1, and 1 IMP-14. CONCLUSIONS This study demonstrates that the detection of CPOs directly from positive BC can be accurately achieved. β CARBA had excellent sensitivity but suffered from poor specificity. CARBA 5 had good sensitivity and specificity but is unable to detect certain CPOs.