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Published on: July 9, 2012
Rapid detection of carbapenemase-producing organisms directly from blood cultures positive for Gram-negative bacilli
William Stokes1,2, Johann Pitout3,4, Lorraine Campbell4
1University of Calgary, Calgary, AB, Canada. william.stokes@ahs.ca.
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.
