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

Specific gene probe detection methods that utilise a non-selective cul turing step were tested for the ability to recognise the presence of q uiescent enteric bacteria (Escherichia coli and Enterococcus faecalis) within illuminated freshwater and seawater microcosms An E. coli spec ific uidA gene probe and a 23S rRNA oligonucleotide probe for Enteroco cci were compared with recoveries using membrane filtration and incuba tion on selective media (mTEC and mE respectively), From these microco sm experiments a greater initial detection (from 4 hours to 1 day) of E. coli and Ent. faecalis using gene probe methods was observed, Addit ionally, a comparison of E. coli direct viable counts (DVC) in sunligh t 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 e nrichment step. The detection of stressed Ent. faecalis by the oligonu cleotide gene probe method was significantly greater than recovery on selective mE agar, indicating an Enterococci non-growth phase.