Comparative analysis of molecular and conventional methods for bacteriological water quality assessment in drinking water resources around Chennai

Coliforms and Escherichia coli represents the fecal contamination in drinking water and hence its potability. The present study estimates uidA and lacZ genes as distinctive biomarkers for rapid and efficient detection of contaminated water resources. Totally 39 environmental water samples were collected in and around the metropolitan city of Chennai, India. The results were compared with culture based method using selective medium. The study shows that the performance and amplification efficiency of uidA and lacZ are 99.6% and 103.4% respectively. The sensitivity of the qPCR method in selectively identifying E. coli was 71.4% in a total of 92.3% coliform contamination. The conventional method showed that 10 samples were positive for E. coli and 12 samples positive for coliforms of total 39 samples. A lower positive predictive value of the biomarkers observed is due to the insignificant association between the two methods and is determined to be 59.0% and 66.6% for E. coli and coliforms respectively. The study reports 50 and 70% of the overhead tank (OHT) samples were contaminated with E. coli and coliform respectively which indicates sanitation measures through these water supplies are not adequately taken care. High throughput molecular detection technique is reported here which can be used for monitoring environmental samples more quickly.