Evaluation of a new medium for the enumeration of total coliforms and Escherichia coli in Japanese surface waters

Abstract

A new medium, EC-Blue-10, containing chromogenic and fluorogenic substrates, KNO(3) and sodium pyruvate has been developed for the rapid simultaneous detection and enumeration of total coliforms and Escherichia coli in water. Two evaluations of EC-Blue-10 were carried out. Firstly, EC-Blue-10 was compared with Colilert-MPN for 96 water samples using MPN for total coliforms and E. coli. Secondly, the detection of coliforms and E. coli were compared using 2400 tubes of EC-Blue-10 and Colilert-MPN. The regression coefficients between EC-Blue-10 and Colilert-MPN for total coliforms and E. coli were 0.91 and 0.89, respectively. For the detection results, the Cohen's kappa values between the two media were 0.79 for coliforms and 0.72 for E. coli. EC-Blue-10 is almost same as Colilert-MPN for the detection of coliforms and E. coli in surface waters. Further evaluation for EC-Blue-10 is needed to verify in different geographical areas. EC-Blue-10 is useful method for the rapid and simultaneous detection of total coliforms and E. coli in water sample.