New strategies for the enumeration of enteric pathogens in water

Authors: Gorski, Lisa; RIVADENEIRA, PAULA - University Of Arizona; Cooley, Michael

Submitted to: Environmental Microbiology Reports
Publication Type: Review Article
Publication Acceptance Date: 7/25/2019
Publication Date: 7/25/2019
Citation: Gorski, L.A., Rivadeneira, P., Cooley, M.B. 2019. New strategies for the enumeration of enteric pathogens in water. Environmental Microbiology Reports. 11(6):765-776. https://doi.org/10.1111/1758-2229.12786.
DOI: https://doi.org/10.1111/1758-2229.12786

Interpretive Summary: Water quality standards for drinking water and recreational waters are based on the counting of fecal coliforms, which indicate potential human fecal contamination. Irrigation water will soon undergo the same scrutiny in the U.S. as part of the Food Safety Modernization Act, which sets the acceptable level of fecal coliforms over a specified testing period at the same level as recreational waters. Accurate counting of bacteria in water is difficult. For over 50 years the Most Probable Number (MPN) method has been used by laboratories to estimate the level of viable bacteria in a sample. This method is labor intensive and slow, especially if large numbers of samples need to be tested. In this review we describe some recently described methods to count potential fecal pathogens in water. These methods are based on different reasoning schemes that can be categorized as biosensors and nucleic acid-based methods. All of the methods described here were tested with natural water sources. Several of the methods were also used to survey the bacterial levels in naturally contaminated samples. The different methods vary in their Limits of Detection (LOD), ease of use, and potential portability. Some methods reviewed here combine very good limits of detection with the ability to overcome challenges in sample types. However, there is considerable room for improvement, as none of the methods are without shortcomings.

Technical Abstract: Water quality standards for drinking water and recreational waters have long been based on the enumeration of fecal coliforms in the various water supplies with 0 CFU Escherichia coli/100 ml for drinking water and <126 CFU generic E. coli/100ml for recreational waters. Irrigation water will soon undergo the same scrutiny in the U.S. For over 50 years the Most Probable Number (MPN) method has been used by laboratories to estimate the level of viable bacteria in a sample, but this method is labor intensive and slow, especially if large numbers of samples need to be tested. In this review we describe some recent innovations in methods to enumerate enteric pathogens in water. These methods are based on different reasoning schemes that can be categorized as biosensors and nucleic acid-based methods. All the methods described here were tested with natural water sources. Several were also used to survey the bacterial levels in naturally contaminated samples. The different methods vary in their Limits of Detection (LOD), ease of use, and potential portability. Some combine very good limits of detection with the ability to overcome technical challenges; however, there is considerable room for improvement, as none of the methods are without shortcomings.