The use of antibiotic-containing agars for the isolation of extended-spectrum beta-lactamase-producing organisms in intensive care units.

MacConkey agar containing either cefotaxime 1.0 mg/L or ceftazidime 1.0 mg/L was evaluated for use in screening for extended-spectrum beta-lactamase (ESBL)-producing organisms. The media were evaluated using known ESBL-positive and -negative strains and 630 clinical specimens over a 6-month period. All Enterobacteriaceae isolated were identified and screened for ESBL production by phenotypic methods. In total, 14 ESBL-producing organisms were detected in the clinical samples. All known ESBL-positive strains were also detected. The use of both screening plates was required to detect all ESBLs.