Four chromogenic urine culture media were compared to culture on blood agar, MacConkey agar, and CLED (cysteine-, lactose-, and electrolyte-deficient) agar for detection of uropathogens in 1,200 urine specimens. After 2 nights of incubation, 96% of all isolates were recovered on blood agar, 96% were recovered on CLED agar, 92% were recovered on CPS ID2, 96% were recovered on CHROMagar Orientation from BBL, 95% were recovered on CHROMagar Orientation from The CHROMagar Company, and 95% were recovered on Chromogenic UTI Medium.Chromogenic media have been compared to traditional urine culture media, e.g., blood agar and MacConkey agar, and been found to be at least as good as traditional media for the isolation of uropathogens (7,9,12,13). In one study, no significant differences between the isolation rates of different chromogenic media were found (2).Three articles reported the effect of incubation time on results of urine culture on traditional media (3,8,11). All agree that common uropathogens can be detected after overnight incubation and that a longer incubation time is required for the detection of yeasts.In this study, we evaluated four different chromogenic agars Blood agar, CLED (cysteine-, lactose-, and electrolyte-deficient) agar, and MacConkey agar were used as the reference media. We also compared overnight incubation to 2 nights of incubation; to our knowledge, this has not been done previously.The media evaluated are listed in Table 1. Blood agar, CLED agar, MacConkey agar, CHROMagar Orientation from The CHROMagar Company, and Chromogenic UTI Medium were prepared at the respective laboratories in accordance with the manufacturers' recommendations.CPS ID2 and CHROMagar Orientation from BBL were received as ready-made agar plates. Media prepared at the laboratories were tested for contamination by incubation of one plate from each batch at room temperature and one plate in ambient atmosphere at 36°C for 2 days.Each batch was also tested for typical colony appearance and growth with Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, and Proteus mirabilis ATCC 29245.The media were compared by using quantitative culture with test strains. In this comparison, 10-l volumes of serial dilutions (starting from approximately 10 8 CFU/ml) of each test strain (E. coli ATCC 25922, E. faecalis ATCC 29212, and S. saprophyticus ATCC 15305) were inoculated onto each medium with a calibrated pipette (Finnpipette; Labsystems). Colonies were counted after 1 and 2 days of incubation in ambient atmosphere at 36°C.The media were also evaluated by using urine specimens sent in for routine culture. The first 50 urine specimens that arrived every day at each laboratory were included in the study. A total of 1,200 urine specimens were inoculated on all of the media tested. The laboratories serve both tertiary care hospitals and primary care centers. Most of the specimens included in the study were from inpatients, as the specimens collected at the ...