This press release is available in Spanish.
U.S. Department of Agriculture (USDA) scientists have come up with a way to detect pathogenic Escherichia coli and Salmonella bacteria in waterways at lower levels than any previous method. Similar methods have been developed to detect pathogenic E. coli in meat products, but the approach by the scientists with USDA's Agricultural Research Service (ARS) represents a first for waterways.
ARS is USDA's principal intramural scientific research agency, and this research supports the USDA priority of ensuring food safety.
When health officials test a public beach or lake for Salmonella or E. coli 0157:H7, they use two types of non-pathogenic bacteria, Enterococci and generic E. coli, as indicators. But while the indicators are often detected in contaminated waterways, their abundance doesn't guarantee the presence of either pathogen, according to Michael Jenkins, a microbiologist at the ARS J. Phil Campbell Sr. Natural Resource Conservation Center in Watkinsville, Ga.
These indicator organisms are often reliable, but investigators have detected the indicators in pathogen-free waters and have failed to find them in waters that contained sufficient levels of the pathogens to make someone sick.
The indicators are used as signals because both pathogens are hard to detect directly at levels that will make someone ill: just 100 cells of Salmonella and just 10 to 100 cells of E. coli 0157:H7, the toxic strain of the bacterium. Organic matter in a water sample will throw off current PCR (polymerase chain reaction) technology when it is used as a tool for detection. Salmonella and E. coli outbreaks are often attributed to agricultural operations, so improving ways to track down sources of outbreaks is a major priority.
Jenkins and his ARS colleagues Di
|Contact: Dennis O'Brien|
United States Department of Agriculture - Research, Education and Economics