|Dorner, Sara - Ecole Polytechnique|
|Wjelan, Gene - Environmental Protection Agency (EPA)|
Submitted to: Critical Reviews in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2014
Publication Date: 11/4/2014
Citation: Pachepsky, Y.A., Shelton, D.R., Dorner, S., Wjelan, G. 2014. Can E. coli or thermotolerant coliform concentrations predict pathogen presence or prevalence in irrigation waters? Critical Reviews in Microbiology. 42(3):384-393. doi:10.3109/1040841X.2014.954524.
Interpretive Summary: In recent years, more than 40% of documented food-borne illnesses have been associated with fresh produce. Irrigation water is a known vector for transmission of pathogenic microorganisms to produce. Microbial quality of irrigation waters is assessed based on concentrations of indicator organisms rather than pathogenic microorganisms. The purpose of this work was to review and analyze all published studies world-wide regarding the accuracy of using thermotolerant coliforms or Escherichia coli as predictors of prevalence and/or concentrations of pathogenic organisms. Collectively, these studies indicate that coliform indicators alone cannot provide conclusive, non-site-specific and non-pathogen-specific information about the prevalence and/or concentrations of the most important pathogens in surface waters suitable for irrigation. Standards for irrigation water cannot be based soley on concentrations of indicators and/or pathogens, but should include references to land use and potential pathogen sources in watersheds. Such information is generally lacking and is needed to support criteria for microbiological risk assessment of irrigation waters. Results of this work can be of use for environmental assessment and regulations in that they provide the evaluation of suitability and limitations of coliform indicators for microbial assessment of irrigation water sources.
Technical Abstract: An increase in food-borne illnesses in the United States has been associated with fresh produce consumption in recent years. The objective of this review was to collate and summarize experimental data on the relationships between pathogens and thermotolerant coliform (THT) and/or generic E. coli, specifically focusing on surface fresh waters used in or potentially suitable for irrigation agriculture. We collected peer-reviewed publications in which concentrations of E. coli or THT coliforms in natural surface fresh waters were measured with concentrations of one or more of the following waterborne and food-borne pathogenic organisms: Salmonella spp., Campylobacter spp., shiga-toxigenic E. coli, Listeria monocytogenes, Cryptosporidium parvum, and Giardia spp. A total of 16629 data points was compiled from 35 papers on coupled, one-time observations of 'THT or E. coli’ versus pathogen. We found a total of 81 datasets for which attempts to establish relationships between E. coli and pathogens (40 datasets) and THT coliforms and pathogens (41 datasets) were reported. The proposed relationships were significant in 28 instances (35%) and not significant in 53 instances (65%). In seven instances a significant relationship was found between E. coli and pathogen(s), while in 21 instances a significant relationship was found between THT and pathogen(s). The relatively low number of established significant ’indicator-pathogen’ relationships could partially be explained by different sources, release patterns, detection capabilities, ecology, environmental fate and transport of the microbes in different indicator and pathogen groups. Overall, coliform indicators alone cannot provide conclusive, non-site-specific and non-pathogen-specific information about the presence and/or concentrations of most important pathogens in surface waters suitable for irrigation. So far only limited attempts were made to couple data on coliform indicators with other types of information to inform on microbiological quality of irrigation waters. Standards of microbial water quality for irrigation cannot rely only on concentrations of indicators and/or pathogens, but must include references to crop management. Critical information on microbial composition of actual irrigation waters to support criteria of microbiological quality of irrigation waters appears to be lacking and needs to be collected.