EVALUATION OF MUG-SUPPLEMENTED MEDIA FOR THE DETECTION OF ESCHERICHIA-COLI IN RECREATIONAL WATER SURVEILLANCE

Four media containing 4-methylumbelliferyl-beta-D-glucuronide were eva luated as a nonconfirmatory procedure for E. coli detection in recreat ional water surveillance. The media included ECD-Agar for membrane fil tration and laurylsulphate-tryptose, brilliant-green bile and lactose as broth media in a three tube most probable number procedure. From si x representative water sites, samples were collected weekly over a typ ical summer season (17.05-27.09.1994) and processed as parallels, usin g each media at two different incubation temperatures (36 degrees/44 d egrees C). Results showed that incubation temperature had no impact on E. coli counts. Each media at a given temperature could be regarded a s individual enrichment procedure. None of these enrichment procedures showed a constant and predictable higher sensitivity during the sampl ing period at all sites compared to the others tested. For parallel re sults, the rate of agreement, based upon EC-guideline (76/160/EWG) sta ging of recreational water quality, was 85% for membrane filtration an d 75% for the MPN-procedure results. Marked differences could be obser ved in false-positive specificity showing correlation to the selective characteristics of the media. Subsequently lactose-broth at 44 degree s C performed worst with 30% non verifiable results, while ECD-agar an d laurylsulphate-tryptose-broth, both at 44 degrees C, had a nearly 10 0% confirmation rate. Thus, combining high specificity with no lack in sensitivity these two MUG-supplemented media seem to be best suited f or E, coli detection in routine recreational water surveillance.