The Development of Gene Probes for Coliforms and Other Micro-Organisms (WMI 9018) Final Report to the Department of the Environment September 1988 to June 1993 DoE 3426/1
Report No DWI0135

Jul 1993

SUMMARY

Gene probe is the term used to describe a novel molecular biological technique which detects pieces of genetic material specific to a species or group of organisms. It has been proposed that gene probes should allow the detection of specific microorganisms with greater speed and certainty than traditional analytical methods.

A major problem in drinking water microbiology is that current methods for the detection of the indicators of microbiological quality (total coliforms and Escherichia coli) take more than 24 h. As a consequence, monitoring can only provide retrospective information about quality.

There has been considerable speculation about how gene probes could revolutionise bacterial detection. In particular, it has been suggested that the time required for analysis of coliforms could be reduced to less than 6 h. This would be of great operational value in the control of drinking water quality.

For this reason the potential value of gene probe techniques in detecting bacteria in drinking water samples needed investigation. The Department of the Environment placed a contract with WRc to assess the potential use of gene probes and where necessary carry out further development specifically for the microbiological analysis of water. This research contract was steered by and carried out under the supervision of the Drinking Water Inspectorate.

This contract was to provide an independent and realistic assessment of the future role of these techniques to monitoring the microbiological quality of drinking water. Two aspects have been investigated:

  1. The application of gene probe techniques to the enumeration of total coliform organisms and E. coli in drinking water.

  2. The application of gene probe techniques to the detection of enteroviruses in drinking water.

The strategy adopted for enumeration of bacteria in drinking waters was to implement the gene probe methods into the existing traditional procedure of membrane filtration. The method appears to work although a robust method, which is significantly more rapid than the traditional method, has not been achieved because of limits in the currently available technologies for visualisation of the gene probes and their detection sensitivities. However, further developments should bring improvements within a few years.

A fundamental step in the detection of viruses by gene probes is the amplification of viral genetic material extracted from the water samples. The best currently available technique called PCR (polymerase chain reaction) was not found to have reached an adequate stage of development for the viruses of health significance in drinking water. However, it was found that PCR could be applied to the detection of nucleic acid material from viruses of interest in other areas of public health.

This is a rapidly developing area of microbiological rapid methods. Whereas the contract has not provided complete robust methods which are directly applicable to the water industry, it has provided a unique insight into shortcomings of current technology and an indication of the immediate potential value of gene probe techniques. The information gained from the studies will also be extremely valuable to others interested in progressing this application of gene probe techniques.

Copies of this report may be available as an Acrobat pdf download under the 'Pre 2000 Reports' heading on the DWI website.