A biomarker to distinguish human from animal waste using the STh toxin gene fragment of Escherichia coli.

摘要

Water has been associated with the transmission of a wide variety of human pathogenic organisms including bacteria, viruses and protozoa via the fecal-oral route. Diseases transmitted through contact with contaminated water continue to be a major global problem, and in the United States alone, between 1920 and 1994, 1,816 outbreaks of waterborne disease occurred with 965,128 illness cases and greater than 1,089 attributable deaths.; Under ideal conditions, it would be possible to detect all disease-causing organisms in waters that can be transmitted to humans. However, the large number and variety of pathogenic of such microorganisms make the direct detection of these organisms impractical. This concern has been addressed via the indicator organism system, which was designed to monitor for a non-pathogenic microorganism associated with the gastrointestinal tract that could be found in the feces of warm-blooded animals. The bacterium, Escherichia coli (E. coli) is one of several indicator organisms. This organism is found in the intestines of both humans and animals. A method that could distinguish between human and animal E. coli sources of contamination would be very useful with regard to reduction of pathogens in water sources.; In this study, the occurrence of th STh toxin gene biomarker was found to be indicative of the presence of E. coli of human origin. Using genetic methods, 421 E. coli strains and DNA extracted from 310 animal fecal samples were screened for the occurrence of this trait. None of the strains or fecal samples were found to contain the DNA for this biomarker. The trait was validated in 125 wastewater samples, where it was found that overall, 93 percent of 1 liter grab samples from wastewater treatment plants of raw influent and final effluent were positive for this trait. The calculated minimum level of detectable STh DNA is 42 × 10−15 g, and at a rate of occurrence of this trait of 1:1000 E. coli cells, a minimum of 9000 E. coli cells is needed to detect this trait. The environmental sample size to detect this trait is calculated to be 7 liters. However, increasing the sensitivity of this test may result in a method that can easily distinguish between human and animal E. coli.