Evaluation of Brilliance CRE Agar for the detection of carbapenem-resistant Gram-negative bacteria

The aim of this work was to evaluate the performance of the new chromogenic medium Brilliance (TM) CRE Agar (Thermo Fisher Scientific) for determining the limit of detection of carbapenem-resistant enterobacteria (CRE). A total of 70 clinical isolates were studied. Of these, 30 were well-characterized CRE, including Klebsiella pneumoniae strains producing KPC-, VIM-, and OXA-type enzymes, VIM-positive Enterobacter cloacae and Escherichia coli, NDM-positive E. coli, and enterobacterial isolates characterized by porin loss associated with ESBL production or AmpC hyperproduction. Ten carbapenem-resistant non-fermentative isolates were also included as well as 30 carbapenem-susceptible isolates. Carbapenem-resistant strains were inoculated at three different concentrations onto Brilliance CRE Agar (from 1.5x10(1) CFU/ml up to 1.5x10(4) CFU/ml) whereas carbapenem-susceptible isolates were inoculated at a concentration of 1.5x10(2) CFU/ml. The medium sustained the growth of carbapenem-resistant isolates, showing detection limits from 1.5x10(1) CFU/ml (in 31/40 cases) to 1.5x10(4) CFU/ml. No growth was observed with carbapenem-sensitive control strains. Our results indicate that the Brilliance CRE Agar allows the growth of carbapenem-resistant isolates with low detection limits and could represent a useful screening medium for both enterobacteria and non-fermentative Gram-negative strains resistant to carbapenems.