COMPARATIVE PERFORMANCE OF COLISURE(TM) AND ACCEPTED METHODS IN THE DETECTION OF CHLORINE-INJURED TOTAL COLIFORMS AND ESCHERICHIA-COLI

Studies were done to examine the comparability of Colisure(TM) and acc epted reference methods to detect low numbers of total coliform bacter ia and E.coli subjected to chlorine stress. Colisure(TM) is a medium d esigned to concurrently detect coliform bacteria and E.coli in drinkin g water by the specific action of beta-galactosidase (total coliforms) and beta-glucuronidase (E.coli). The methods used to compare the perf ormance of various media followed a protocol established by the USEPA. Samples (31)of sewage from six different regions of the US were treat ed with sufficient concentrations of chlorine (1.2-2.5mg/l) to reduce viability 1-3 logs (39% average injury) and diluted with drinking wate r to achieve ca. 3 viable coliforms/100ml. The mean log reductions in viable bacteria, determined with various media following disinfection of the 31 samples were: mEndo = 1.87 (TC), Colisure(TM) = 1.55 (TC), m Tec = 3.63 (E.coli) and Colisure(TM) = 2.01 (E.coli). When Colisure(TM ) was compared with accepted methods to detect total coliforms in the dilute, disinfected samples, Colisure(TM) yielded results that were 1. 6 times greater than LTB confirmed in BGLB at 28h. Colisure(TM) also d etected 1.7 times greater levels of E.coli than LTB confirmed in EC/MU G at 28h. Sensitivity and specificity of Colisure(TM) were between 96 and 100% when positive and negative tests were verified. These finding s indicate that Colisure(TM) is superior to certain accepted reference methods in the detection of chlorine-injured coliforms and E.coli und er conditions that resemble contaminated drinking water.