Evaluation of Total Bacteroides As an Alternative Irrigation Water Quality Indicator.

Preharvest irrigation water represents a key potential source of pathogenic bacteria during the production of fresh produce. Widespread crop contamination can occur if irrigation water is contaminated with fecal pathogens, such as Escherichia coli (E.coli) and Salmonella. Industry guidance standards uniformly identify generic E. coli as a practical and cost‐effective indicator of fecal contamination in water. However, although generic E. coli satisfies most characteristics of an ideal bacterial indicator, only very limited correlation exists between the presence of E. coli, pathogen presence, and microbial risk to consumers following consumption of contaminated produce. This work examines an alternative fecal indicator bacterial group, Total Bacteroides, for prediction of pathogen presence in 102 irrigation water samples collected throughout Arizona. Total Bacteroides markers were enumerated by quantitative Polymerase Chain Reaction (qPCR), using: 1) a published protocol, and 2) a commercially-available Bacteroides enumeration kit. Each water sample was also assayed for generic and pathogenic E. coli and Salmonella markers, to assess correlations between Bacteroides markers and human pathogens. Ultimately, this project will determine the utility of Total Bacteroides as an indicator of human pathogens in water used for irrigation of fresh produce, information critical to continued production of a safe and sustainable food supply in the United States.