Occurence of pathogenic and indicator microorganisms on produce irrigated with dairy wastewater

Persistent Link:
http://hdl.handle.net/10150/289980
Title:
Occurence of pathogenic and indicator microorganisms on produce irrigated with dairy wastewater
Author:
Manshadi, Faezeh Dehghan
Issue Date:
2003
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This project was designed to assess the potential for contamination of produce during irrigation with wastewater from animal operations. Dairy wastewater from the University of Arizona Campus Dairy Research Center was used to irrigate three different types of vegetable crops: lettuce, carrot, and bell pepper. This study was conducted over two consecutive years. The crops were planted in February and vegetables were harvested from May through July. Irrigation water and vegetable samples were examined for Escherichia coli, Clostridium perfringens, Listeria monocytogenes, and coliphage. In the dairy wastewater, E. coli concentrations averaged 5.7 x 10⁵ MPN/100 mL in the first year (2000), and 9.9 x 10⁷ MPN/100 mL in the second year (2001). C. perfringens concentrations were nearly the same in both years (1.7 x 10⁴ and 3.4 x 10⁴ CFU per 100 mL). Coliphage averaged 2.0 PFU/mL in 2000 and 1.3 x 10⁴ PFU/mL in 2001 in wastewater. E. coli was detected with greater frequency on carrots (100 and 96%) succeeded by lettuce (67 and 96%) and bell peppers (63 and 58%). The same was true for C. perfringens : carrots (100%), lettuce (86 and 88%), and bell peppers (100 and 50%). Coliphages were not detected on any of the vegetable crops except for average concentrations of 2 PFU/g on lettuce in the first year. L. monocytogenes was not detected on any of the vegetable samples. ANOVA test results indicates that E. coli and C. perfringens concentrations on three crops were statistically different (p < 0.0001) which suggest that the degree of contamination on the surface of the vegetables depends on where the edible portion of the crop is situated (above the soil or under the soil). The greatest contamination occurred on the carrots followed by lettuce and bell peppers. E. coli and C. perfringens were recovered from the carrots, bell peppers, and soil 55 days after wastewater irrigation of the plots had ceased. Positive correlations (p < 0.05) were found between E. coli and C. perfringens density and soil moisture content. The greatest risk of infection from pathogenic E. coli (O157:H7) occurs from consumption of lettuce and carrots. The annual risk of infection from consumption of all three vegetables was above the acceptable risk of 1:10,000 per year. The results of this study suggest that a more strict irrigation water quality standard for root and leafy vegetables might be appropriate to prevent the risk of infection in exposed population.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Agriculture, Food Science and Technology.; Biology, Microbiology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Soil, Water and Environmental Science
Degree Grantor:
University of Arizona
Advisor:
Gerba, Charles P.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleOccurence of pathogenic and indicator microorganisms on produce irrigated with dairy wastewateren_US
dc.creatorManshadi, Faezeh Dehghanen_US
dc.contributor.authorManshadi, Faezeh Dehghanen_US
dc.date.issued2003en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis project was designed to assess the potential for contamination of produce during irrigation with wastewater from animal operations. Dairy wastewater from the University of Arizona Campus Dairy Research Center was used to irrigate three different types of vegetable crops: lettuce, carrot, and bell pepper. This study was conducted over two consecutive years. The crops were planted in February and vegetables were harvested from May through July. Irrigation water and vegetable samples were examined for Escherichia coli, Clostridium perfringens, Listeria monocytogenes, and coliphage. In the dairy wastewater, E. coli concentrations averaged 5.7 x 10⁵ MPN/100 mL in the first year (2000), and 9.9 x 10⁷ MPN/100 mL in the second year (2001). C. perfringens concentrations were nearly the same in both years (1.7 x 10⁴ and 3.4 x 10⁴ CFU per 100 mL). Coliphage averaged 2.0 PFU/mL in 2000 and 1.3 x 10⁴ PFU/mL in 2001 in wastewater. E. coli was detected with greater frequency on carrots (100 and 96%) succeeded by lettuce (67 and 96%) and bell peppers (63 and 58%). The same was true for C. perfringens : carrots (100%), lettuce (86 and 88%), and bell peppers (100 and 50%). Coliphages were not detected on any of the vegetable crops except for average concentrations of 2 PFU/g on lettuce in the first year. L. monocytogenes was not detected on any of the vegetable samples. ANOVA test results indicates that E. coli and C. perfringens concentrations on three crops were statistically different (p < 0.0001) which suggest that the degree of contamination on the surface of the vegetables depends on where the edible portion of the crop is situated (above the soil or under the soil). The greatest contamination occurred on the carrots followed by lettuce and bell peppers. E. coli and C. perfringens were recovered from the carrots, bell peppers, and soil 55 days after wastewater irrigation of the plots had ceased. Positive correlations (p < 0.05) were found between E. coli and C. perfringens density and soil moisture content. The greatest risk of infection from pathogenic E. coli (O157:H7) occurs from consumption of lettuce and carrots. The annual risk of infection from consumption of all three vegetables was above the acceptable risk of 1:10,000 per year. The results of this study suggest that a more strict irrigation water quality standard for root and leafy vegetables might be appropriate to prevent the risk of infection in exposed population.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectAgriculture, Food Science and Technology.en_US
dc.subjectBiology, Microbiology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineSoil, Water and Environmental Scienceen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorGerba, Charles P.en_US
dc.identifier.proquest3108927en_US
dc.identifier.bibrecord.b44829425en_US
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