Summary of Awards to Date

Assessment of E. coli as an indicator of microbial quality of irrigation waters use for produce.


Jan. 1, 2012 - Dec. 31, 2012

Award Number


Funding Agency

Center for Produce Safety

Amount Awarded



Channah Rock, Ph.D.
University of Arizona


C. Gerba, K. Bright



The goals of this project are to evaluate currently available detection methods for the accurate assessment of Escherichia coli contamination in irrigation waters and provide guidance for interpretation of results through a revised risk based E.coli standard. Currently, there is concern that the false positive rate of E.coli detection may be high in these waters giving false indications of the level of risk from enteric pathogens. This may result in unnecessary costly interventions as well as inaccurate perception of risk among consumers. We propose evaluating three different commercial systems for E.coli detection in irrigation waters and assessing false positive rates by use of molecular technologies. As a secondary objective to evaluating E.coli as a reliable indicator, we propose using a Quantitative Microbial Risk Assessment (QMRA) to assess the use of E.coli as an accurate indicator of food safety risk using data collected in the first stage of this project coupled with existing information found in the scientific literature. Ultimately this work will offer recommendations towards the most reliable methods to be used by the produce industry to assess irrigation water contamination as well as a scientific risk-based E.coli guideline that growers can use to protect public health.