Direct detection of major carbapenemases from positive blood cultures using the NG-TEST® Blood Culture PREP kit combined with NG-TEST® CARBA 5

Background Rapid detection of Gram-negative carbapenemase-producing organisms (CPOs) in bloodstream infections is crucial to guide timely therapy. We assessed the performance of the NG-TEST ® CARBA 5 (NG Biotech) combined with the NG-TEST ® Blood Culture PREP (BCP) Kit for direct detection of the five main carbapenemases from positive blood cultures. Methods A total of 145 clinical Enterobacterales were used to spike blood culture bottles. These included 124 CPOs with targeted carbapenemases (18 NDM-, 10 VIM-, 28 IMP-, 24 KPC-, 31 OXA-48-like, and 13 multiple carbapenemases), 10 CPOs with no targeted carbapenemases, and 11 non-CPOs. Blood cultures were placed in the BACT/ALERT ® VIRTUO® system (bioMérieux) until bacterial growth was detected by the system. Bacteria were produced using the NG-TEST ® BCP Kit, followed by the NG-TEST ® CARBA 5. The results were compared to those from colonies. Results The NG-TEST ® BCP Kit reliably extracted bacteria irrespective of the bacterial species. The NG-TEST ® CARBA 5 identified 134 of the 138 carbapenemases from bacterial pellets from blood cultures and 136 of the 138 from bacterial colonies, resulting in 97.10% and 98.55% sensitivity, respectively. As expected, KPC-31 and KPC-33 were missed in both cases, but two VIM-producing C. freundii were only detected from colonies. Non-targeted CPOs and non-CPOs gave negative results, confirming 100% specificity. Conclusion Our results show that combining the NG-TEST ® BCP Kit with the NG-TEST ® CARBA 5 provides a rapid (<25 min), user-friendly, robust, and accurate method for species-independent detection of the five main carbapenemases directly from positive blood cultures, enabling earlier targeted antimicrobial therapy in bloodstream infections.