Study on the efficiency of four procedures for enumerating coliforms in water

Four coliform estimation procedures were compared as to their ability to enumerate coliform bacteria (oxidase-negative lactose fermenters) from sewage, effluent, and various fresh waters in the lower Great Lakes Region of Canada. Two of the procedures used and which are cited in the American Public Health Association (APHA) Standard Methods were a most probable number (MPN) technique using lauryltryptose broth (LST) and brilliant green bile 2% broth (BGB), and a membrane filtration (MF) technique using m Endo agar LES. The other two procedures were an MPN technique using Parhad chemically defined synthetic medium (PCDS) and BGB developed for Indian fresh waters and an MF (mC agar) technique developed for seawater. Data indicate that within the survey area, maximum population estimates were achieved by the MF procedure using m Endo agar LES and that each procedure was selective for different genera of the Enterobacteriaceae. Discussions concerning standard versus reference procedures are presented.