Field evaluation of a rapid portable test for monitoring fecal coliforms in coastal waters

Two hundred beachwater samples were collected along the New South Wales coast, Australia, and analyzed for fecal coliforms in the field using a portable, 60 min fluorimetric assay of beta-D-galactosidase activity. The aim of the study was to evaluate the reliability of the technique alongside a standard membrane filtration procedure to assess fecal contamination of coastal bathing waters. The assay had a 98% success rate at predicting whether the coliform concentrations of the samples were greater than, or less than, 300 fecal coliforms per 100 ml (the current limit of detection of the method). The results over which the two methods were in disagreement comprised less than 2% false positives [where the rapid method indicated greater than and membrane filtration indicated less than 300 colony-forming units (cfu) per 100 ml] and no false negatives (where the rapid method indicated less than and membrane filtration indicated greater than 300 cfu per 100 ml). The described assay provides a rapid, simple, and inexpensive method for the detection of fecal contamination in marine waters. As analyses can be performed in the field, the technique offers great potential for near real-time monitoring of water quality and as an "early warning" system for contamination of bathing waters. (C) 1999 by John Wiley & Sons, Inc.