Performance of a new in-house medium Carba MTL-broth for the rapid detection of carbapenemase-producing Enterobacteriaceae

Introduction: The spread of carbapenemase-producing Enterobacteriaceae (CPE) represents a major public health issue. Methods allowing rapid detection of carbapenemases in developing countries are therefore urgently needed. In the current study, we developed a new in-house medium for the rapid detection of CPE isolates, especially OXA-48 producers.

Methodology: A panel of 144 clinical strains previously characterized was tested on in-house Carba MTL-broth medium using four different concentrations of ertapenem (0.5 to 2 mg/L), and compared to chromID® OXA-48 and chromID® CARBA (BioMérieux) media.

Results: Comparative evaluation of the Carba MTL-broth with chromID® OXA-48 and chromID® CARBA showed that chromID® OXA-48 and Carba MTL-broth had the highest sensitivity for detection of OXA-48 producers (93.9% and 100%, respectively) comparatively to chromID® CARBA (21.2%). The chromID® OXA-48 had the highest specificity (100%), as compared to the Carba MTL-broth (65.5%) and chromID® CARBA (84.4%) for the detection of OXA-48 producers.

Conclusions: The in-house Carba MTL-broth developed in this study is sensitive, inexpensive, an easy-to-use phenotypic method for the detection of OXA-48-producing enterobacteria. Given the burden of pan-drug resistance, its implementation in the microbiology laboratory of developing countries could be a useful tool for rapid detection of these bacteria.