Ertapenem Supplemented Selective Media as a New Strategy to Distinguish β-Lactam-Resistant Enterobacterales: Application to Clinical and Wastewater Samples

Abstract

The increase in carbapenem-resistant Enterobacterales (CRE) is mostly driven by the spread of carbapenemase-producing (CP) strains. In New Caledonia, the majority of carbapenemases found are IMP-type carbapenemases that are difficult to detect on routine selective media. In this study, a culture-based method with ertapenem selection is proposed to distinguish non-CRE, non-CP-CRE, and CP-CRE from samples with very high bacterial loads. Firstly, assays were carried out with phenotypically well-characterized β-lactam-resistant Enterobacterales isolates. Then, this approach was applied to clinical and environmental samples. Presumptive CP-CRE isolates were finally identified, and the presence of a carbapenemase was assessed. In a collection of 27 phenotypically well-characterized β-lactam-resistant Enterobacterales, an ertapenem concentration of 0.5 µg.mL−1 allowed distinguishing CRE from non-CRE. A concentration of 4 µg.mL−1 allowed distinguishing CP-CRE from non-CP-CRE after nine hours of incubation. These methods allowed isolating 18 CP-CRE from hospital effluents, including the first detection of a KPC in New Caledonia. All these elements show that this cost-effective strategy to distinguish β-lactam-resistant Enterobacterales provides fast and reliable results. This could be applied in the Pacific islands or other resource-limited settings, where limited data are available.

MacErt Culture Media: A Cost-Effective Selective Media for Carbapenemase Producing Enterobacterales isolation

“…Comparatively, previously proposed culture media had limitations [5,8]. For instance, the direct MacConkey media, although designed for screening carbapenem-resistant Gram-negative rods in stool samples, exhibited low sensitivity due to the direct addition of imipenem, meropenem, and ertapenem discs [9][10][11].…”

“…This is particularly worrisome, given that carbapenems, viewed as the last line of defense against severe infections, are increasingly compromised [1,2]. The ability of CPEs to rapidly acquire and transfer resistance genes, combined with their high potential for dissemination, underscore the importance of their detection and surveillance [3][4][5].…”

MacErt Culture Media: A Cost-Effective Selective Media for Carbapenemase Producing Enterobacterales Surveillance

“…Carbapenemase Producing Enterobacterales (CPEs) have become a signi cant global concern in recent years, posing a serious threat to public health as carbapenems are considered the last resort for treating severe infections [1,2]. The ability of CPEs to rapidly acquire and transfer resistance genes, combined with their high potential for dissemination, makes their detection and surveillance crucial [3][4][5].…”