Evaluation of BBL CHROMagar orientation medium for detection and presumptive identification of urinary tract pathogens

Abstract

The microbiological performance of BBL CHROMagar Orientation medium and CPS ID2 agar was compared to that of Columbia agar with 5% sheep blood and MacConkey agar without crystal violet for the enumeration and presumptive identification of bacteria responsible for urinary tract infections. Of a total of 658 clinical urine specimens, 118 specimens yielded no growth, 402 specimens yielded growth with cell counts of >10 5 CFU/ml, and 138 specimens yielded growth with cell counts of <10 5 CFU/ml. Of the specimens with cell counts of >10 5 CFU/ml, 163 were pure cultures and 239 were mixed cultures. A total of 266 Escherichia coli organisms were isolated on both chromogenic media, 260 were isolated on blood agar, and 248 were isolated on MacConkey agar. One strain (0.4%) failed to develop the expected pink color on CHROMagar Orientation medium, and 23 strains (8.7%) failed to develop the expected pink color on CPS ID2 agar. Enterococci (CHROMagar Orientation medium, n ‫؍‬ 266; CPS ID2 agar, n ‫؍‬ 265) produced small blue-green colonies on both chromogenic media. Fifty of the mixed cultures contained enterococci that were detected only on the chromogenic media. The Klebsiella-Enterobacter-Serratia (KES) and the Proteus-Morganella-Providencia (PMP) groups could be identified on both chromogenic media. Of 66 isolates of the KES group, 63 grew with the expected color on CHROMagar Orientation medium and 58 of 64 isolates grew with the expected color on CPS ID2 agar. Other microorganisms required further identification. The use of chromogenic medium formulations offers a time-saving method for the reliable detection, enumeration, and presumptive identification of urinary tract pathogens. One of the greatest advantages of these media is the easy recognition of mixed cultures.For several years chromogenic media that allow for the direct identification of the most frequently isolated bacterial and fungal species, such as CPS ID2, SMID agar, and Albicans ID (BioMérieux), Rambach agar (CHROMagar), and BBL CHROMagar Candida (Becton Dickinson), have been available for use with either urine samples or stool specimens or for the identification of yeasts (1,2,9,12,19,22,(24)(25)(26).Since the diagnosis of urinary tract infections contributes significantly to the daily workload in a microbiology laboratory, any innovation that tends to reduce the workload is always welcome when a high-quality standard is still maintained.Our objectives were to evaluate the accuracy of BBL CHROMagar Orientation medium and CPS ID2 agar compared to those of conventional media (Columbia agar with 5% sheep blood and MacConkey agar without crystal violet) for the detection and enumeration of the organisms commonly involved in urinary tract infections and to compare the ability of both chromogenic media to correctly identify the more frequently occurring organisms or organism groups with only a minimum of confirmatory tests.Apart from specimens with clinically significant organism counts (Ն10 5 CFU/ml), we included specimens with Ͻ10 5 CFU/ml in order to evalu...

Comparative evaluation of three chromogenic agars for detection and rapid identification of aerobic Gram-negative bacteria in the normal intestinal microflora

“…To our knowledge DR of Enterobacteriaceae in stool specimens are not known from other studies using chromogenic media. The DR corresponded well, however, to the rates of urinary tract pathogens described in previous studies using these media [1,2]. Hengstler et al did not ®nd any differences in the recovery of Gram-negative bacteria from urine specimens between the two chromogenic media and the MacConkey agar [2].…”

Chromogenic Agar Medium : A Versatile Tool for the Diagnosis of UTI

“…Over the last few years, several chromogenic urine culture media have been developed and commercialized, allowing more specific and direct differentiation of microorganism on the primary plate itself 7,12,13,14 . Chromogenic medium designed to isolate and identify all uropathogens.…”

“…An important aspect of HiCrome UTI agar is that it allows an easy differentiation of various species from mixed cultures due to specific colony colour 17,8 . Another advantage of this chromogenic agar medium is that it can be used to perform antibiotic sensitivity testing without subculture onto another basic medium 7,12,14 .…”

Cost-Effective and Rapid Presumptive Identification of Gram-Negative Bacilli in Routine Urine, Pus, and Stool Cultures: Evaluation of the Use of CHROMagar Orientation Medium in Conjunction with Simple Biochemical Tests

“…The media most widely used for the isolation and differentiation of coliform gram-negative bacteria and other enteric pathogens from clinical specimens are MacConkey agar in the United States and modified Drigalski agar in Japan, but their ability to differentiate these types of organisms is minimal because they depend only on determination of lactose utilization. Several proprietary chromogenic mixtures, which have been available for some years, allow the presumptive identification of pathogenic organisms on the basis of colonial morphology and distinctive color patterns (9,11,12,17). CHROMagar Orientation medium is a chromogenic culture medium that is usually used for the isolation and enumeration of urinary tract pathogens.…”

“…It has several advantages, such as a greater ability to differentiate gram-negative bacilli, and facilitates the detection as well as presumptive identification of gram-negative bacilli (12). Several previous studies have shown that it can serve as a primary isolation and reliable differentiation medium for urinary tract pathogens, including gramnegative bacilli, enterococci, and staphylococci (9,12,17). However, its suitability for use with clinical specimens other than urine samples has not been assessed.…”