Use of ChromID extended-spectrum beta-lactamase medium for detecting carbapenemase-producing Enterobacteriaceae.

ChromID extended-spectrum beta-lactamase (ESBL) culture medium is routinely used for screening ESBL producers. This medium was tested for detecting carbapenemase-producing Enterobacteriaceae isolates from a collection of reference strains and compared to the CHROMagar KPC culture medium previously evaluated for detecting KPC-producing isolates. Producers of IMP-, VIM-, and KPC-type carbapenemases with high levels of resistance to cephalosporins and to carbapenems were detected at 1x10(1) CFU/ml. The OXA-48 producers were not detected on ChromID ESBL medium unless coexpressing ESBLs, whereas carbapenemase-producing isolates with MICs of <4 microg/ml were not detected on CHROMagar KPC medium.