Objective: The aim of this study was to evaluate the performance of the ChromID ESBL agar (bioMérieux, France) for the presumptive identification of extended spectrum beta lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae isolates.

Materials and Methods: A total of 115 isolates (90 E. coli and 25 K. pneumonia) with confirmed ESBL production were inoculated onto ChromID ESBL agar to evaluate the growth selectivity and chromogenic features of the medium.

Results: Of the 90 E. coli isolates, 83 (92.2%) produced the expected red-burgondy colony color on ChromID ESBL agar, five (5.6%) displayed light brown colonies which were regarded as the species of the PMP (Proteus/Morganella/Providencia) group according to the expected chromogenic features provided in the manufacturers' specifications. Two E. coli strains did not grow on ChromID ESBL agar. Of the 25 K. pneumoniae isolates, 24 (96%) produced the expected green colony color on ChromID ESBL agar whereas one isolate did not grow on the medium. For E. coli isolates the sensitivity of ChromID ESBL agar for ESBL detection was 97.8% and for ESBL detection together with correct species identification was 92.2%. For K. pneumoniae isolates the sensitivity of ChromID ESBL agar for ESBL detection with correct species identification was 96%.

Conclusion: ChromID ESBL agar is a useful and sensitive medium for rapid presumptive identification of ESBL-producing E. coli and K. pneumoniae isolates.