Rapid monitoring of Escherichia coli in Southeast Asian urban canals by fluorescent-bacteriophage assay

The microbial water quality in canals of metropolitan Bangkok, Thailand, was assessed using the fluorescent bacteriophage assay (FBA) and fluorescence in situ hybridization (FISH). When FISH was used with oligonucleotide probes targeted to Escherichia coli (E. coli) and anaerobic Bacteroides group, < 0.1% to 7% and < 0.1% to 11%, respectively, of the total bacteria were identified. Estimates of viable E. coli determined by FBA with 4′,6-diamidino-2-phenylindole (DAPI)-labeled T4 bacteriophage, which accounted for 1 to 8% of total cells, were significantly higher than those of fecal coliforms determined by the most probable number method. The FBA procedure can specifically detect viable E. coli in canal water samples that are grossly contaminated with fecal flora within 30 min, and it can quickly deliver accurate findings for risk assessment of environmental contamination in water samples.