Evaluation of the NG-TEST® blood culture PREP kit for ESBL directly from positive blood cultures using the NG-TEST® CTX-M MULTI lateral flow immunoassay

Abstract Background ESBL-producing Enterobacterales are a major cause of bloodstream infections, requiring rapid detection for timely antimicrobial therapy. We evaluated the performance of the NG-TEST® CTX-M MULTI lateral flow immunoassay combined with the NG-TEST® Blood Culture Prep (BCP) Kit for detecting CTX-M ESBLs directly from positive blood cultures. Methods In total 165 clinical Enterobacterales were used to spike blood culture bottles. These included 32 non–CTX-M producers, 120 CTX-M producers belonging to the five main CTX-M groups, and 13 Kluyvera sp. Blood cultures were placed in the BACT/ALERT® VIRTUO® system (bioMérieux); upon bacterial growth detection by the system a UriSelect 4 Agar (Bio-Rad) was inoculated to verify purity. Bacteria were prepared using the NG-TEST® BCP Kit followed by the NG-TEST® CTX-M MULTI. Results The NG-TEST® CTX-M MULTI detected all 120 CTX-M–producing isolates expressing CTX-M variants belonging to the five groups (1, 2, 8, 9 and 25) from both colonies and blood cultures, resulting in 100% sensitivity. The NG-TEST® BCP Kit removed all the patients’ blood cells and reliably extracted bacteria irrespective of the bacterial species. Non–CTX-M producers gave negative results, confirming 100% specificity. Among CTX-M–producing Kluyvera species, eight isolates tested positive, while five were repeatedly negative, and consistent with prior reports. Conclusions Our results demonstrate that the combination of the NG-TEST® BCP Kit and the NG-TEST® CTX-M MULTI systems provides a rapid (20 min), user-friendly, robust and accurate tool for species-independent detection of CTX-M–type ESBLs directly from positive blood cultures, supporting earlier targeted antimicrobial therapy in bloodstream infections.