Chromogenic Agar Medium Research Articles

Use of Chromogenic Agar Media for Identification of Uropathogen

Chromogenic agar media are increasingly being used as versatile tools in early differentiation and identification of Gram positive and Gram negative isolates from clinical specimens. We have evaluated the chromogenic medium as it’s use reduces the burden of biochemical characterization and reduces the workload for identification of bacteria. This study included 400 consecutively collected midstream and/or catheter-catch urine samples obtained from patients attending the hospital out patient department (OPD) and also from patients admitted in BSMMU hospital. They were inoculated on blood agar, MacConkey agar, cystine lactose, electrolyte deficient media and chromogenic agar plate for isolation of uropathogen. Out of 400 urine samples tested, 154 (38.5%) yielded significant growth of single organism and 16 (4%) yielded mixed growth. No growth was observed in 230 (57.5%) cases. The chromogenic agar media allowed the growth and primary identification in 171 (92.5%) strains out of 186 strains. The predominant uropathogens were Escherichia coli, Klebsiella spp. Enterococcus spp. and Eneterobacter spp. (KES group). The different coloured colonies produced by the breakdown of the chromogenic substrate by the specific enzymes of the bacteria were very useful in the presumptive identification of these organisms even from polymicrobial cultures by the color differences of the colonies. The medium also supported growth and differentiation of Gram positive organisms like Staphylococcus and Enterococci. Chromogenic agar media can be used as primary culture medium for isolation and identification of predominant uropathogens like E.coli, KES group and Enterococci. It is an easy to use primary screening medium that considerably reduces the daily workload and thus minimizes or limits the use of identification tests. Key words: Chromogenic agar medium, KES, CLED media, UTI DOI: http://dx.doi.org/10.3329/bjmm.v4i1.8464 BJMM 2011; 4(1): 18-23

Comparative evaluation of chromogenic agar medium and conventional culture system for isolation and presumptive identification of uropathogens.

Objective: Urine is the most frequent specimen received for culture/sensitivity by clinical laboratories. The microbiological performance of HiCrome UTI agar medium was compared with Blood agar and MacConkey agar for isolation and presumptive identification of bacteria from urine culture. Methods: A total of 443 consecutively collected midstream and/or catheter-catch urine samples from patients attending the Islami Bank Medical College Hospital, Rajshahi, Bangladesh during January to December, 2012 were cultured. Urine samples showing pus cells ≥ 5/HPF were inoculated on to Blood agar (BA), MacConkey agar (MAC) and HiCrome UTI agar (CA) media simultaneously and incubated overnight aerobically at 370C. Rate of isolation and presumptive identification of bacterial species were compared for different media. Results: Culture yielded a total of 199 bacterial isolates from 189 (42.67%) positive plates including 179 (40.40%) unimicrobial and 10 (2.26%) polymicrobial (mixed growth of pair of bacteria) growths. Both HiCrome UTI agar and Blood agar media supported 100% growths while 151 (75.88%) growths were observed on MacConkey agar. The rate of presumptive identification was found significantly higher on HiCrome UTI agar (97.49%) than MAC agar (67.34%) (P<0.001) as primary urine culture medium. Of 199 isolates, E. coli was found to be the leading uropathogen isolated from 118 (59.30%) samples with its presumptive identification rate of 95.76%, 93.22% and 5.93% on CA, MAC and BA respectively. All 10 (100%) polymicrobial growths were demonstrated distinctly on CA against only 01(10%) on each BA and MAC. Conclusion: HiCrome UTI agar was found to be more useful as primary urine culture medium in both higher rate of isolation and presumptive identification of uropathogens in comparison to conventional media. Its inherent characteristics in demonstrating polymicrobial growth and ease of rapid identification by distinct colony colour are unique.