T6-11 Assessing the Microbial Risk of Soil, Irrigation Water, and Farm Worker Hands to Produce Contamination on Farms and Packing Sheds Near the U.S.-Mexico Border

Tuesday, July 30, 2013: 11:30 AM
213D (Charlotte Convention Center)
Juan Leon, Emory University, Atlanta, GA
Faith Bartz, Emory University, Atlanta, GA
Anna Fabiszewski de Aceituno, Emory University, Atlanta, GA
Jacqueline Lickness, Emory University, Atlanta, GA
Alice Parish, Emory University, Atlanta, GA
Norma Heredia, Universidad Autónoma de Nuevo Leon, Monterrey, Mexico
Santos Garcia, Universidad De Nuevo Leon, San Nicolas De Los Garza, Mexico
Lee-Ann Jaykus, North Carolina State University, Raleigh, NC
Introduction: Produce associated enteric disease outbreaks are responsible for serious economic losses, morbidity, and mortality. Few studies have directly identified routes of contamination at the farm or packing shed.

Purpose: The goal of our study was to quantify microbial levels in potential environmental sources of contamination (soil, irrigation water, farm worker hands) and identify their role in produce contamination.

Methods: From 2011-2012, 237 produce composite (cantaloupe, jalapeño, tomato) and 121 matched irrigation water, 79 soil, and 158 farm worker hand rinse composite samples were collected from 10 farms on the Mexican side of the U.S.-Mexico border. From each sample, generic Escherichia coli, enterococci, fecal coliforms, and coliphages were enumerated. The magnitude of association between produce and environmental sample contamination was assessed by chi-square tests and logistic regression models (prevalence data), Spearman’s correlations (non-normal concentration data), and linear regression models (concentrations). Human ethical research approval (IRB) was secured.

Results: In general, farm worker hand samples had higher concentrations of fecal indicators than soil or water samples. Soil had the lowest prevalence of fecal indicators compared to hands and water samples. Pooling data across the two years of sample collection, the concentrations of E. coli (rho = 0.9), enterococci (rho = 0.5), coliforms (rho = 0.3), and coliphage (rho = 0.7) were significantly and highly correlated between hands and produce, but not between soil or water and produce. The presence of E. coli, enterococci, and coliphage was significantly associated between hands and produce (odds ratios ranged between 2.3 - 8.5 across indicators), but not between soil or water and produce. These trends were also observed when analyses were adjusted for crop type and processing.

Significance: These results suggest that decreasing farm worker hand contamination would be an effective intervention to decrease microbial contamination of produce in the study region.