|Year : 2015 | Volume
| Issue : 1 | Page : 183-184
Evaluation of new chromogenic media for identification of uropathogens from complicated urinary tract infections in a tertiary healthcare setting
B Mohan, P Gupta, SB Appannanavar, G Singh, N Taneja
Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, Punjab, India
|Date of Submission||06-Sep-2013|
|Date of Acceptance||31-Jan-2014|
|Date of Web Publication||5-Jan-2015|
Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, Punjab
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mohan B, Gupta P, Appannanavar S B, Singh G, Taneja N. Evaluation of new chromogenic media for identification of uropathogens from complicated urinary tract infections in a tertiary healthcare setting. Indian J Med Microbiol 2015;33:183-4
|How to cite this URL:|
Mohan B, Gupta P, Appannanavar S B, Singh G, Taneja N. Evaluation of new chromogenic media for identification of uropathogens from complicated urinary tract infections in a tertiary healthcare setting. Indian J Med Microbiol [serial online] 2015 [cited 2019 Nov 12];33:183-4. Available from: http://www.ijmm.org/text.asp?2015/33/1/183/148427
Urinary tract infections (UTIs) are one of the most common infections encountered in a hospital setting.  ChromID CPS agar (bioMιrieux, Marcy l'Etoile, France) is a chropmogenic, non-selective, differential medium developed for identification of various uropathogens isolated from urine specimens. Since ours is a high through put laboratory, we wanted to assess if use of this chromogenic medium would be beneficial in routine by cutting down on time to identify and minimise the use of biochemical test. As a pilot study, we evaluated the utility and cost effectiveness of ChromID CPS agar for the isolation and identification of uropathogens and compared with in house cystine-lactose-electrolyte-deficient (CLED) agar (regularly assessed for quality). Urine culture was performed on 210 samples using both the chromogenic and CLED agar medium. ChromID CPS agar (here after referred to as 'chromogenic media') incorporates two colour producing substrates, which enable the direct identification of bacteria by detection of activities of specific enzyme, β-glucuronidase, β-glucosidase and deaminase. The bacteria could be easily identified by difference in colour of the colony [Figure 1]. Out of 210 urine samples, 96 (45.7%) were culture positive on chromogenic medium as compared with 67 (31.9%) samples on CLED. Positive urine cultures were unimicrobial in 67 (31.9%) and 55 (26.19%) and polymicrobial in 29 (13.8%) and 12 (5.71%) on chromogenic medium and CLED, respectively. Chromogenic medium was superior to CLED: A higher detection of positive urine cultures on chromogenic medium was observed as compared with CLED agar ( 96 vs 67, P < 0.05). Therefore, the chromogenic medium was significantly less likely to miss a positive culture and it significantly picked up polymicrobial culture better than CLED (31% vs 18%, P value-0.007). Both these findings denote that the chromogenic medium can be highly valuable in setting like ours where more than 90% of cases are of complicated and counts of <10 5 and polymicrobial infections are expected.  Proportions and differences in proportions (along with 95% CI) calculated using Medcalc statistical software are shown in [Table 1]. Higher number of strains of Klebsiella pneumoniae (16, P value-0.01), Enterococcus (34, P value-0.04), Streptococcus agalactiae (8, P value-0.01) and Yeast species (30, P value-0.001) were identified on chromogenic medium as compared with CLED. Few strains of Escherichia More Details coli (9), Pseudomonas aeruginosa (3), Acinetobacter spp (4) Proteus mirabilis (1), Citrobacte freundii (1) and Morganella morganii (1) did not produce expected colony colour on chromogenic medium. Thus, chromogenic medium allowed identification of 83% of the isolates within 24 h itself, whereas on CLED it took 48 h to confirm all the isolates biochemically. The chromogenic medium was found to be facilitating the growth of Gram-positive bacteria as it successfully detected the growth of all S. agalactiae and S. saprophyticus, which failed to grow on CLED. This was in concordance with the previous study done by Carigill et al.  As shown in other studies, Enterococcus species was easy to differentiate especially in a polymicrobial culture.  An easy differentiation of isolates in a mixed culture may avoid the unnecessary antibiotic treatment and additional work for isolation. But similar to previous studies, few isolates E. coli (19.14%), P. aeruginosa (42.85%), P. mirabilis (12.5%) failed to produce expected colour and appeared colourless.  C. freundii, M. morganii and Acinetobacter species also did not produce any colour and thus required further identification. As observed by other workers too, the identification of the KESC group was only presumptive and required further identification for definite speciation. 
|Table 1: Comparison of identification of organisms isolated from urine samples (n=210) using the chromogenic medium and CLED medium along with biochemicals |
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By cost analysis chromogenic medium was found to be cost efficient because it gave improved isolation, better and rapid identification within 24 h itself obviating the need for biochemical tests in 83% of the samples. In conclusion, chromogenic medium can be used as a primary culture medium for rapid identification of uropathogens. Chromogenic medium gave results in 24 h, thus facilitating early initiation of therapy. It reduces the workload considerably by limiting the use of different media and biochemical tests. Though the initial cost of media is high, this disadvantage could be offset by better diagnosis in monomicrobial and polymicrobial culture positive cases.
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