Fecal (animal and/or human waste) contamination of water supplies is a constant concern for water treatment facilities. Water treatment facilities monitor for fecal contamination of their water by checking for the presence of bacteria that are normally found in feces. A very common organism found in feces is Escherichia coli (E. coli). Water treatment plants test their water for the presence of E. coli very frequently. If E. coli is present in the water they know some sort of fecal material is getting in their water.
Unfortunately, most animals also have E. coli in their feces, and if water is contaminated with E. coli no one knows for sure where the contamination is coming from. Migrating bird feces could be contaminating the water. A cattle feedlot may have a lagoon that is overflowing. A pig-lot lagoon overflow or improperly treated human waste might be getting into the water. With so many possible sources of contamination it can be very difficult to find the problem and correct it.
Meanwhile, people are drinking water that could potentially make them ill.
To aid in identifying the sources of fecal contamination researchers from the University of Missouri reported in the April 2001 issue of the journal, Applied and Environmental Microbiology on a test that can differentiate between human and animal sources of fecal contamination. They are using a test called ribotyping.
Basically, the researchers grew E. coli from humans and various animals (cattle, pig, goat, turkey, horse, chicken, goose) and looked for differences in a specific location in their DNA. This portion of the DNA codes for ribosomal RNAs (rRNA)is called 16S and 23S rRNA.
Ribosomal RNA together with various proteins make up the cell structure called a ribosome. The ribosome is the table on which protein is made. 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.
Based on other studies, it has been shown that different strains of E. coli can be identified by looking at small differences in the DNA that codes for these 16S and 23S rRNA's. When ribotyping was used to differentiate E. coli from humans and animals it had an accuracy of over 97 percent. It also had a high degree of accuracy in identifying which animal the E. coli came from.
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