Evaluation of the Chromogenic Medium ( CPS ) in the Isolation and Identification of Urinary Tract Pathogens

Abstract

Background: Urine cultures constitute the majority of the workload for a microbiology laboratory with only 20%-30% of urine sample resulting in significant growth. Chromogenic media (CM) are available for urine specimens to enable rapid identification of common pathogens and also has been reported to increase mixed culture detection, reducing unnecessary workup. Chromogenic media offers the potential to lower costs by providing decreased work time, storage space and identification costs. Objectives: The present study focused on evaluation of the chromogenic medium (CPS) for the diagnosis of UTI in comparison with CLED as a conventional medium. Methodology: Over the period of January to July 2014, fifty urine samples with ≥100 pus cells /HPF were examined. CPS and CLED media were used for direct inoculation in addition to conventional biochemical reactions and/or API as needed. Results: In comparison with CLED, CPS showed a sensitivity of 93.5%, specificity of 100%, positive predictive value of 100%, negative predictive value of 57.1% and total agreement of 94%. The sensitivity of CPS for E. coli was 95%, for KESC was 75%, for Proteeae was 100% and for Enterococcus was 100%. The specificity of CPS for detection of E. coli was 100%, for KESC was 100%, for Proteeae was 97.9% and for Enterococcus was 100%. Conclusion: CPS proved to be a rapid, cost-effective diagnostic method for urinary tract infections. Therefore, CPS can replace the standard primary plating media used in routine diagnosis of urinary tract infection.