Fast and cheap DNA based analyses for E. Coli
Conventional commercial systems for identifying E.coli were considered to be expensive and time consuming. They were also unsuitable for analysing the large volume of samples involved in a screening programme. In response the ANTRES project developed a reliable and cost-effective system for identifying E.coli using filter DNA hybridisation. Researchers chose two different target genes for developing species specific DNA probes. These were the lacZ gene, which encoded galactosidase and the uidA gene, which encoded glucuronidase. These genes have been employed previously for creating DNA probes for identifying E.coli. Each probe was tested in a series of colony blot experiments against reference strains of various species of bacteria. During this process the uidA probe was found to be the more accurate of the two probes and was chosen to be developed further. The uidA probe was validated using a sub sample of isolates. The results were compared with those obtained using the conventional API 20E bacterial identification system. The two different methods agreed on almost all the isolates. Therefore, the colony blot method based on the uidA probe was considered to be a suitable technique for identifying E.coli. The new system was less time consuming and a tenth of the cost of the conventional technique. Therefore, it was adopted for use in identifying E.coli in the ARS baseline study.
