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ARS Home » Midwest Area » Bowling Green, Kentucky » Food Animal Environmental Systems Research » Research » Publications at this Location » Publication #313593
Title: Environmental E.coli isolate characterization and selection as improved indicators for pathogens associated with produce contamination

Author
item Cook, Kimberly - Kim
item GIVAN, ETHAN - Western Kentucky University
item TAYLOR, RITCHIE - Western Kentucky University

Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2015
Publication Date: 4/14/2015
Citation: Cook, K.L., Givan, E., Taylor, R. 2015. Environmental E.coli isolate characterization and selection as improved indicators for pathogens associated with produce contamination. 2015 Kentucky Public Health Association Conference. April 14-16, 2015. Owensboro, Kentucky.

Interpretive Summary: Contamination of food and water by pathogens is a substantial public health issue in the United States. According to the Centers for Disease Control and Prevention, 49% of foodborne illness is caused by produce, and despite efforts to reduce produce contamination, these issues persist. Escherichia coli are often used as an indicator, or surrogate, for pathogens for quality control and food safety research. However, it is evident that present surrogates being used are not adequate indicators for pathogen contamination of produce. Research is needed to find superior surrogates for produce pathogens to provide the food industry and researchers a more effective indicator of produce pathogens. In this study, 63 E. coli isolates were selected from a pool of 1,346 isolates taken from animal and surface water sources. These 63 environmental E.coli isolates, the produce related pathogens Salmonella, Listeria, E. coli O157:H7 and a common quality control E.coli strain were evaluated for biofilm formation, curli expression, and growth rate. When comparing the quality control strain, E.coli O157:H7 and Listeria to the 63 isolates, the 63 isolates had higher biofilm formation when grown in LM. Six of the 63 isolates had biofilm formation that was three times higher than the quality control strain. Salmonella biofilm formation was approximately 15 times higher than that of the common quality control strain when grown in LM. This research will provide science based information on the differences in E. coli isolates from multiple environmental sources, the selection of better produce pathogen surrogates, and the potential public health impact this research can have.

Technical Abstract: Contamination of food and water by pathogens is a substantial public health issue in the United States. According to the Centers for Disease Control and Prevention, 49% of foodborne illness is caused by produce, and despite efforts to reduce produce contamination, these issues persist. Escherichia coli are often used as an indicator, or surrogate, for pathogens for quality control and food safety research. However, it is evident that present surrogates being used are not adequate indicators for pathogen contamination of produce. Using Escherichia coli as a surrogate for produce pathogens should aid in research to understand the sources of contamination and how these pathogens persist in the soil and on plant surfaces. A key step in using E. coli as a pathogen surrogate is to understand how this organism varies in the environment relative to produce pathogens so that the most representative surrogate can be selected. Research is needed to find superior surrogates for produce pathogens to provide the food industry and researchers a more effective indicator of produce pathogens. In this study, 63 E. coli isolates were selected from a pool of 1,346 isolates taken from animal and surface water sources. These 63 environmental E.coli isolates, the produce related pathogens Salmonella, Listeria, E. coli O157:H7 and a common quality control E.coli strain were evaluated for biofilm formation, curli expression, and growth rate. These assays were completed when isolates were grown in a nutrient rich environment (Luria-Bertani broth [LB]) and a nutrient poor environment (Lettuce lysate + minimal salts [LM]). These characteristics are thought to play major roles in the ability of pathogens to survive and persist in the soil and on plant surfaces. When comparing the quality control strain, E.coli O157:H7 and Listeria to the 63 isolates, the 63 isolates had higher biofilm formation when grown in LM. Six of the 63 isolates had biofilm formation that was three times higher than the quality control strain. Salmonella biofilm formation was approximately 15 times higher than that of the common quality control strain when grown in LM. This data exemplifies the diversity in isolates from environmental sources, and that E.coli quality control strains may not be appropriate indicators of pathogens. Using this data, and continued characterization of the isolates (carbon source utilization, genotypic data, soil and lettuce adhesion), isolates will be selected for future greenhouse experiments. These isolates will then be applied to soil and lettuce leaf substrates via spray or drip irrigation water, and isolate survival will be monitored over time. This research will provide science based information on the differences in E. coli isolates from multiple environmental sources, the selection of better produce pathogen surrogates, and the potential public health impact this research can have.