Detection of Escherichia coli in potable water using direct impedance technology.

Direct impedance measurement utilizing a medium previously described as being specific for Escherichia coli and which contains trimethylamine N-oxide (TMAO) and glucuronic acid was used to detect E. coli in water samples. The system was compared with the Colilert presence/absence test and the United Kingdom standard membrane filtration technique using membrane lauryl sulphate broth. The impedance method correlated well with both the traditional membrane method (93%) and the Colilert method (93.95%) for a number of different water types. No interference from Citrobacter spp. (as reported in previous studies) was detected in this study although some Salmonella spp. did give false-positive results. The data presented here suggest that the use of direct impedance may offer an alternative to conventional methods for the detection of E. coli in water.