Home : Services : E. coli Source Tracking Toolbox^TM: E. coli ID^TM

Determine sources of E. coli contamination.

(must be done in conjunction with theE. coli Comparison ID™ Service)

E. coli isolates are compared to an internal library of E. coli strains to indicate a probable source, either human or animal (or both).

Specific animal sources are then determined with comparison samples using the E. coli Comparison ID™ service.

Send as little as 100ml of water. (Agar plates and soil samples also accepted.)

Results in 8 to 21 working days.

No laboratory work or kits involved.

Uses DNA fingerprinting technology.

Important Note: The website and the services offered are for environmental professionals. This website is only a cursory overview of the services offered. Source Molecular is not responsible for errors or omissions on the web site. Furthermore, clients must understand the limitations of the services before submitting samples. Please call beforehand to discuss service details and type of samples to be submitted.

Source Molecular offers on a routine basis DNA fingerprinting (i.e. ribotyping) services to determine sources of E. coli contamination.^1,*

Where is the source of contamination coming from?

DNA fingerprinting using ribotyping can answer that question. Often, likely sources of contamination are suspected, but difficult to prove. For example, if water regulators suspect that a local dairy farm is contributing to the E. coli contamination of the municipal groundwater supply, a DNA fingerprinting analysis can be performed to see whether the E. coli in question is from cows.^(*) A positive result indicating E. coli from cattle would help remedy the contamination problem more easily than through cumbersome traditional tracking methods.

The Source Molecular DNA fingerprinting service (E. coli ID™) makes in an initial probabilistic determination whether E. coli is from a human or an animal source (or both). Afterwards, animal-specifc subsets of E. coli are differentiated by analyzing comparison samples (e.g. cow dung) from local regions. These comparison samples are compared to other samples (e.g. groundwater samples) to see if there is a DNA "match".^(*)

What is Ribotyping?

After cultivating E. coli from the submitted sample, one or more E. coli isolates are selected. Isolates are clusters of E. coli colonies on an agar plate. A DNA fingerprinting analysis called ribotyping is performed on each E. coli isolate selected. This genetic fingerprint comes from genes that code for ribosomal ribonucleic acids (rRNA) of E. coli. Ribosomal RNA together with various proteins makes up the cell structure called a ribosome.

The ribosome is the cell structure where proteins are manufactured. In order to produce proteins, the messenger RNA and the amino acids are transferred to the ribosome. As the ribosome moves down the messenger RNA, it places the correct amino acid in the growing protein. It has been shown that looking at small differences in the DNA that code for these 16S and 23S rRNA’s help identify different strains of E. coli.

Ribosomal genes are also known to be highly conserved in microbes, meaning that the genetic information coding for rRNA will vary much less within bacteria of the same strain than it will between bacterial strains. This characteristic allows for a greater ability to distinguish between different bacterial strains.

In ribotyping, restriction enzymes are used to cut the genes coding for rRNA into pieces, and electrophoresis separates the pieces by size through a gel.^2,4 Genetic probes then visualize locations of different-size fragments of DNA in the gel, which appear as bands. The banding pattern of DNA fragments corresponding to the relevant rRNA is known as the ribotype. The banding patterns are compared to a database of other E. coli strains and matched for each determined strain. If the client submits fecal samples, then banding patterns are also investigated between the fecal samples and blind samples submitted.⁵

For an overview of DNA fingerprinting and its application for the water industry, please click here.

For a complete list of prices and disclaimers, please consult our Price List page.

E. coli ID™ : DNA Fingerprinting of E. coli: Fecal coliform enumeration and DNA ribotyping analysis of 5 E. coli isolates.

Service makes an initial determination if E. coli is from human or animal sources. Specific animal sources are then determined with comparison samples.