The use of CHROMagar Orientation as a primary isolation medium with presumptive identification for the routine screening of urine specimens

The aim of the study was to compare the use of a novel differential culture medium CHROMagar, for both primary isolation and presumptive identificatio n, with the method currently used in our laboratory for screening mid-strea m-urine samples (MSU). Routine methods (RM) included blotting paper imprint ing of all specimens and additional quantitative culture on cysteine lactos e electrolyte-deficient agar (CLED) for selected samples together with Micr obact 12E for further identification. The CHROMagar method (CH) relied on t he use of blotting paper imprints, colonial colour and morphology on CHROMa gar only. With respect to the 3390 MSU specimens examined, both methods yie lded similar results in 3240, including greater than or equal to 87% of Esc herichia coli, Pseudamonas spp., Staphylococcus spp., Proteus milabilis/Mor ganella morganii and Enterobacter/Serratia/Klebsiella/Citrobacter spp. Of t he 52 discordant identifications, yeasts were reported as staphylococci on CHROMagar in 10. The overall cost of materials per specimen was US$0.30 by RM and $0.24 by CH. It took about 3 min to perform each Microbact test. Thu s, CHROMagar plus Gram stain and other simple bench tests gave results simi lar to those using our current method, but had the advantage of saving time and materials.