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Microbial Risk Assessment of Water Used in the Production of Produce in Arizona

Objective

<OL> <LI> Assess the microbial quality of water used in the production of produce in Arizona. <LI> Determine the relationship between the microbial quality of water used and the type of microbial contamination found on the produce. <LI> Using risk analysis procedures determine the potential for illness to occur, as well as identify priorities in addressing any potential hazards.

More information

NON-TECHNICAL SUMMARY: The increased incidence of microbial food-borne illnesses associated with fresh or minimally processed produce has increased concern over their safety. This concern is occurring at a time when there is increasing demand by consumers and promotion by health agencies of these food items. Microbial contamination of produce may occur at any or multiple points in the food system from farm to table. The microbial quality of water used in production can have a direct impact on the microbial quality of the produce items. This project will assess the microbial quality of water used in the production (e.g., irrigation, chemical application, product processing) of produce in Arizona. This area is important because of its increasing contribution to the U.S. produce market, particularly during the winter months. The relationship between the microbial quality of water used and the type of microbial contamination found on the produce will also be a focal point of this study. Risk analysis procedures will be used to determine the potential for illness to occur, as well as identify priorities in addressing any potential hazards. Results of this research project will be used to develop educational materials and programs to extend research based knowledge to produce producers. This project will also be involved in providing training on good agricultural practices to establishments or individuals involved in produce production, processing, distribution, and retailing.

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APPROACH: Water, manure, and produce samples will be evaluated. In addition to obtaining samples, information specific to each growing area will be recorded and used in the final analysis. Sampling will be conducted on a monthly basis and at harvest at each study area. Sampling will be conducted on a monthly basis during the growing season. All study areas will be analyzed for E. coli, Salmonella, Small Round Structured Viruses, Giardia, and Cryptosporidium. In addition to monthly sampling, sampling during high risk periods such as periods of significant rain fall will also be conducted. At time of application to the field manure-based fertilizers will be analyzed for E. coli, Salmonella, Giardia, and Cryptosporidium. At time of harvest 50 to 100 pieces of produce will be examined for E. coli, Salmonella, SRSV, Giardia and Cryptosporidium. External wash water obtained from four to six vegetables of the type being sampled will be assayed. The project manager will have the responsibility for (QA/QC) review during the entire project. Since sample collection will be conducted at multiple locations standardized collection and sampling methods will be established at the beginning of the project. A training workshop will be held to ensure standardization of both sampling and analysis methods. The efficiency of recovery of the pathogens by the methods used will be assessed. Viral contamination of samples will be assessed by reverse-transcription polymerase chain reaction (RT-PCR). To assess the relative concentration of SRSV an MPN dilution procedure will be used. Turbidity, pH, ammonia, and dissolved solids measurements will also be done according to methods described in Standard Methods for the Examination of Water and Waste Water. The current methods described in Standard Methods for the Examination of Water and Waste Water with modifications will be used for the detect of Cryptosporidium and Giardia. Standard culture techniques will be used for the detection of Salmonella. Confirmed Salmonella isolates will be sent to USDA-APHIS Reference laboratory, Ames, IA for species identification. Once information on the occurrence of pathogens or indicators is available in the irrigation water, other sources of crop exposure, or on the crop itself it is possible to conduct a risk assessment to estimate exposure with the efficiency of the sampling and detection methods taken into consideration. The occurrence of pathogens in the water, in manure-based fertilizers and on produce, will be compared to the level of indicator organism (i.e., E. coli). Water turbidity, temperature, pH, flow rate, and total dissolved solids measurements will be compared to the levels of indicator organisms and pathogens.

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PROGRESS: 2000/09 TO 2004/09<BR>
Environmental factors and produce practices influence the microbial quality of produce. The objective of this study was to determine the microbial quality of irrigation water used for the production of fresh produce in Arizona and factors, which may influence this water quality such as canal size, location and rainfall. A total of 117 samples were collected from irrigation canals in Yuma County between June 2001 and March 2003 and 263 water samples were collected in Maricopa County between May 2002 and February 2003. Parameters such as temperature, turbidity, conductivity and pH were recorded for all samples. Water samples were analyzed for microbial indicators which included total coliforms, Escherichia coli, Enterococcus, and Clostridium perfringens. Sampling sites were examined for the presence of Giardia spp., Cryptosporidium spp., Noroviruses, Salmonella spp. and Campylobacter spp. Samples collected in Yuma County showed that 4.3% of the samples were positive for Giardia spp., 19.6% were positive for Cryptosporidium spp., 17.4% were positive for Noroviruses, 20.7% were positive for Salmonella spp. and 55.2% were positive for Campylobacter spp. Overall, results from samples collected in Maricopa County showed that 2.3% of the samples were positive for Cryptosporidium spp, 18.2% were positive for Noroviruses, 28.9% were positive for Salmonella spp. and 68.7% were positive for Campylobacter spp. Giardia spp. were not detected in any samples. One-way ANOVA did not demonstrate any significant difference between microbial indicator concentrations in samples collected from Yuma and Maricopa Counties. Overall, E. coli concentrations correlated strongly with Enterococcus (r=0.858) in samples collected from Maricopa County. Rainfall within 7 days prior to sampling correlated strongly with overall averages for each indicator, the strongest correlation was seen with E. coli (r=0.726). Overall, the main canals tended to have lower microbial numbers than the lateral/drain canals. In Maricopa County, the sampling sites located furthest north and furthest south on each of the main canals tended to have the higher microbial numbers. The sampling points located furthest south tended to be ranked higher in terms of microbial loads. There appeared to be no positive correlation between the levels of microbial indicators and enteropathogens in this study.
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IMPACT: 2000/09 TO 2004/09<BR>
The use of indicator organisms to assess or predict water quality with respect to the presence of entereopathogens, under the conditions of this study, was not efficacious.

Investigators
Meer, Ralph
Institution
University of Arizona
Start date
2000
End date
2004
Project number
ARZT-324780-G-21-516
Accession number
186466