Pig E. coli ID^TM

Determine quickly if your water source has swine fecal contamination.

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.

Since swine are known to harbor human pathogens such as Salmonella spp. and pathogenic E. coli proper monitoring and remediation of this form of fecal contamination is essential for maintaining viable water systems.

The Pig E. coli ID^TM service is designed around the principle that certain strains of E. coli are specifically pathogenic in swine. These enterotoxigenic E. coli (ETEC) can be used as indicators of swine fecal contamination.¹ Enterotoxigenic E. coli have toxin genes that render them pathogenic. These ETEC toxin genes can serve as DNA biomarkers.

It has been shown that the heat stable toxin II (STII) gene from enterotoxigenic E. coli can serve as a reliable indicator of swine fecal contamination.^2,5 Although this toxin gene has on rare occasions been associated with other mammals such as cattle or humans, it is on the whole endemic to swine.³ As such, the STII toxin gene is used as an indicator of swine fecal contamination because 1) it is relatively species-specific, 2) its nucleotide sequence is unique to swine, and 3) of its more frequent occurrence in swine then other toxin genes such as StaP (heat stable toxin I associated with pigs), LT (heat labile), and StaH (heat stable toxin associated with humans) .⁴

One of the advantages of this method is that the entire population of E. coli of the selected portion of the water sample is screened. As such, this method avoids the randomness effect of selecting isolates off a petri dish.² It has been shown that if the total E. coli count (irrespective of the volume of water) of the sample is equal to or greater than 35, the reliability of the analysis is significantly greater, particularly in regards to negative results.

Accuracy of the results is possible because the method uses PCR DNA technology. PCR allows quantities of DNA to be amplified into large number of small copies of DNA sequences. This is accomplished with small pieces of DNA called primers that are complementary and specific to the genomes to be detected.

Through a heating process called thermal cycling, the double stranded DNA is denatured and inserted with complementary primers to create exact copies of the DNA fragment desired. This process is repeated rapidly many times ensuring an exponential progression in the number of copied DNA. If the primers are successful in finding a site on the DNA fragment that is specific to the genome to be studied, then billions of copies of the DNA fragment will be available for detection by gel electrophoresis.

The gel electrophoresis apparatus uses an electrical field to distinguish different DNA fragments according to their molecular weights. Lighter DNA fragments will move farther along the gel than their heavier counterparts. At the end of the procedure different bands of accumulated DNA fragments will aggregate at different parts of the gel. It is this accumulation of DNA fragments that creates a band on the gel. Researchers use these bands to distinguish certain genomes such as the STII toxin gene from enterotoxigenic E. coli.

These banding patterns confirm or negate the presence of the STII toxin gene from the E. coli of the water sample. As such, the banding patterns provide a reliable indicator of swine fecal contamination. To strengthen the validity of the results, the Pig E. coli ID^TM service should be combined with other DNA analytical services such as the Pig Fecal Virus ID^TM service.

¹ Khatib L, Tsai YL, Olson BH.2003. A biomarker for the identification of swine fecal pollution in water using the STII toxin gene from Enterotoxigenic E. coli. Applied Microbiology and Biotechnology.