Background: The increasing incidence of infections caused by Carbapenemase-producing Enterobacterales (CPE) emerging worldwide at an alarming rate becomes a significant clinical and public health concern. The aim of the study was to compare the performance of three chromogenic media: CHROMID® CARBA SMART agar (bioMérieux), a bi-plate for the screening of CPE, Brilliance™ ESBL/Brilliance™ CRE agar (Thermofischer), a bi-plate for the detection of ESBL producers and carbapenem-resistant Enterobacterales, and BD BBL™ CHROMagar™ CPE agar for CPE screening.
Materials/methods: A total of 54 strains: 42 Enterobacterales (10 Escherichia coli, 23 KESC (Klebsiella, Enterobacter, Serratia, Citrobacter) and 9 Proteae) harboring various types of carbapenemase (11 NDM, 6 KPC, 8 OXA 48 or OXA 48 like, 4 VIM), 5 resistant to carbapenems but carbapenemase-negative, 7 ESBL producers and 1 carbapenem-susceptible were selected to evaluate the performance of each carbapenemase medium. Seven non-fermenting Gram negative bacilli (NFGNB): 6 carbapenemase and 1 ESBL producers and 5 other species (3 enterococci, 1 S. aureus and 1 C. albicans) were added. Strains were diluted in saline solution at 1.5×105 CFU/mL and inoculated on each medium. After 18h and 24h of incubation, the presence of growth and coloration of colonies were recorded for each medium.
Results: The overall sensitivity of each medium (all species) for the detection of CPE was respectively 76.9%, 68.3% and 61.5% for CHROMID® CARBASMART, Brilliance™ CRE, and BD BBL™ CHROMagar™ CPE at 18h of incubation and 82.1%, 83.7% and 64.1% at 24h of incubation. Regarding the performance of each medium for the claimed species only (E. coli and KESC for CHROMID® CARBASMART, E. coli, KESC and NFGNB for Brilliance™ CRE, and E. coli, KESC, proteae group for BD BBL™ CHROMagar™ CPE), the sensitivity reached respectively 95.8%, 75%, and 57.6% for the three media. The specificity of each medium was respectively 80% for CHROMID® CARBASMART and BD BBL™ CHROMagar™ CPE and 100% for Brilliance™ CRE agar at 18h and 24h.
Conclusions: CHROMID® CARBASMART shows a better sensitivity of detection of Carbapenemase- producing Enterobacterales compared to Brilliance™ CRE and BD BBL™ CHROMagar™ CPE at 18h and 24h. Specificity of Brilliance™ CRE is higher than CHROMID® CARBASMART and BBL™ CHROMagar™ CPE agar which remains acceptable due to the number of specimens tested.