USE OF GENE PROBES FOR THE DETECTION OF QUIESCENT ENTERIC BACTERIA IN MARINE AND FRESH-WATERS

Specific gene probe detection methods that utilise a non-selective culturing step were tested for the ability to recognise the presence of quiescent enteric bacteria (Escherichia coli and Enterococcus faecalis) within illuminated freshwater and seawater microcosms An E. coli specific uidA gene probe and a 23S rRNA oligonucleotide probe for Enterococci were compared with recoveries using membrane filtration and incubation on selective media (mTEC and mE respectively), From these microcosm experiments a greater initial detection (from 4 hours to 1 day) of E. coli and Ent. faecalis using gene probe methods was observed, Additionally, a comparison of E. coli direct viable counts (DVC) in sunlight exposed microcosms with recoveries by selective media and gene probe methods revealed a large number of viable non-culturable cells, This suggests that enumeration of E. coli by a gene probe method is limited by the replication of the bacteria during the initial non-selective enrichment step. The detection of stressed Ent. faecalis by the oligonucleotide gene probe method was significantly greater than recovery on selective mE agar, indicating an Enterococci non-growth phase.