Rapid detection of CTX-M-type ESBLs and carbapenemases directly from biological samples using the BL-DetecTool

Lateral flow immunoassays (LFIA) have shown their usefulness for detecting CTX-M- and carbapenemase-producing Enterobacterales (CPEs) in bacterial cultures. Here, we have developed and validated the BL-DetecTool to detect CTX-M enzymes and carbapenemases directly from clinical samples.The BL-DetecTool is an LFIA that integrates an easy sample preparation device named SPID (Sampling, Processing, Incubation and Detection). It was evaluated in three University hospitals on urine, blood culture (BC) and rectal swab (RS) specimens either of clinical origin or on spiked samples. RS evaluation was done directly and after a 24 h enrichment step.The CTX-M BL-DetecTool was tested on 485 samples (154 BC, 150 urines, and 181 RS) and revealed a sensitivity and specificity of 97.04% (95% CI 92.59%-99.19%) and 99.43% (95% CI 97.95%-99.93%), respectively. Similarly, the Carba5 BL-DetecTool was tested on 382 samples (145 BC, 116 urines, and 121 RS) and revealed a sensitivity and specificity of 95.3% (95% CI 89.43%-98.47%) and 100% (95% CI 98.67%-100%), respectively. While with the Carba5 BL-DetecTool five false negatives were observed, mostly in RS samples, with the CTX-M BL-DetecTool, in addition to four false-negatives, two false-positives were also observed. Direct testing of RS samples revealed a sensitivity of 78% and 86% for CTX-M and carbapenemase detection, respectively.BL-DetecTool showed excellent biological performance, was easy-to-use, rapid, and could be implemented in any microbiology laboratory around the world, without additional equipment, no need for electricity, nor trained personnel. It offers an attractive alternative to costly molecular methods.