DIAGNOSTIC ACCURACY OF CHROMAGARTM ECC FOR DETECTION AND ENUMERATION OF ESCHERICHIA COLI AND COLIFORMS IN WATER SAMPLES
Objective: To determine the diagnostic accuracy of CHROMagarTM ECC for detection and enumeration of Coliforms and E. coli in water samples keeping the membrane filtration method as gold standard.
Material & Methods: This comparative cross-sectional was conducted from June to December 2019 in Department of Microbiology, AFIP, Rawalpindi, Pakistan with a sample size of 336. Both the membrane Filtration technique and CHROMagarTM ECC media were employed for enumerating E. coli and Coliforms in water samples. Data was analyzed and processed on SPSS version 22.
Results: The water samples tested had E. coli average count of 38 CFU/100 ml on CHROMagarTM ECC as compared to 43 CFU/100 ml on MacConkey agar by Membrane filteration Method. For Coliforms, average colony count on CHROMagarTM ECC was 46 CFU/100 ml as compared to 49 CFU/100 ml on MacConkey agarby Membrane filteration method. For detection and enumeration of Coliforms on CHROMagarTM ECC against Membrane filteration method, the Sensitivity was found 56.8 %, specificity 43.1%, positive predictive value 95.3%, negative predictive value 96.5% and diagnostic accuracy 0.95 (95%).For detection and enumeration of E.coli on CHROMagarTM ECC against Membrane filteration method, the Sensitivity was 44.3%, specificity 55.6%, positive predictive value is 92.7%, negative predictive value is 95.1% and diagnostic accuracy is 0.94 (94%).
Conclusion: This study suggested that the CHROMagarTM ECC is a unique method that can be incorporated in the routine methods of laboratory for bacteriological examination of water to detect bacterial contamination
Key Words: CHROMagarTM ECC, Coliforms, E. coli, Fecal contamination, Membrane Filtration Technique, Water contamination.