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

Background : Culture media play a crucial role in the identification of bacterial pathogens. This study aimed to evaluate the performance of MacErt1 and MacErt2 culture media, for the selective detection of Carbapenemase-Producing Enterobacterales (CPEs) Methods : MacErt1 and MacErt2 were formulated by supplementing MacConkey agar with 0.5 mg/L and 1 mg/L of ertapenem, respectively. The two media were assessed using a panel of 26 characterized Enterobacterales, including CPEs producing OXA-48, NDM, and KPC. Then, the media were employed under realistic conditions for the analysis of wastewater. For each wastewater sample, 10 ml was filtered, and the membrane was placed on MacErt agar, followed by overnight incubation. Subsequently, colonies underwent further examination. Antimicrobial susceptibility tests and Conventional PCR targeting bla _OXA-48-like , bla _NDM , bla _KPC , bla _VIM , and bla _IMP were conducted on the colonies to assess carbapenem resistance genes presence. Results : MacErt1 exhibited excellent sensitivity (100%) for NDM, KPC, and OXA-48-like producers, while MacErt2 showed a sensitivity of 60% for OXA-48-like CPEs but maintained high sensitivity (100%) for NDM and KPC producers. MacErt1 and MacErt2 exhibited specificities for CPEs of 93% and 71%, respectively. The application of MacErt1 to wastewater samples yielded a sensitivity of 100% and a specificity of 83% for CPEs. Conclusions : The study underscores the efficacy and cost-effectiveness of MacErt1 and MacErt2 culture media, in detecting CPEs. MacErt1 exhibits 100% sensitivity across all CPEs, with 83% specificity in wastewater samples. MacErt2, with a specificity of 93% and 100% sensitivity for NDM and KPC producers, emerges as an excellent choice when targeting these specific strains.