Comparison of Multiple Tube Fermentation and Polymerase Chain Reaction Methods for the Detection of Coliforms in Freshwater

Background and objective: Detection of microbial pathogens in water is one of the major health issues. Escherichia coli species are used as indicators of fecal contamination in water microbial detection. In this study, efficacies of two methods of multiple tube fermentation and polymerase chain reaction have been compared for the detection of coliforms (especially Escherichia coli) in water. Material and methods: To compare multiple tube fermentation and polymerase chain reaction methods, 15 water samples were collected from five different sources (three gutter, six well, three tap and three bottled mineral water samples). The samples were cultured in lactose broth media to achieve the most probable number of bacteria. Furthermore, acetate cellulose filter method was used for the bacterial DNA extraction to investigate lacZ (indicating the presence of coliforms) and uidA (indicating the presence of Escherichia coli) genes. Results and conclusion: Based on the results of multiple tube fermentation, eight (53.3%) and six (40%) samples were contaminated with coliforms and Escherichia coli, respectively. Furthermore, polymerase chain reaction results showed that ten (66.7%) and eight (53.3%) samples contained coliforms and Escherichia coli, respectively. Results have suggested that polymerase chain reaction is much faster, more accurate and more sensitive than traditional methods (e.g. multiple tube fermentation) for the detection of coliform contaminated water. Moreover, several types of bacteria can be tracked simultaneously by M-PCR.