Produce Safety and Farmworker Hands: Microbial Contamination of Produce is Positively Associated with Contamination of Farmworker Hands in U.S-Mexico Border Farms

Introduction: Several recent produce related foodborne disease outbreaks have highlighted the need to better understand how, and at what point in production, produce is becoming contaminated. Because there have been few studies examining the routes of contamination in farms and packing sheds, we aim to identify and quantify the contribution of environmental factors in farms (soil, irrigation water, farm worker hands) to produce contamination risks. Methods: Produce (cantaloupe, jalapeņo, tomatoes) rinse samples (161), were collected from 14 farms on the Mexican side of the U.S.-Mexico border, along with matched irrigation water (89), soil (55), and farm worker hand rinse samples (106). From these samples, fecal indicators (E. coli, Enterococcus, coliforms) and human pathogens (Salmonella, E. coli O157:H7) were enumerated. Multivariate regression modeling was used to identify relationships between the microbial quality of the environmental samples and produce. Results: The concentrations of bacterial indicators were significantly higher (p < 0.05) on farm worker hands, and were found at higher levels than in water or soil. The presence of E. coli was significantly associated between hands and produce (OR 7.9, 95%CI [3.3-19.1]), and the levels of E. coli (rho=0.4), Enterococcus (rho=0.5), and coliforms (rho=0.6) were significantly and highly correlated between hands and produce. Discussion: These findings will aid in focusing future interventions to decrease produce contamination risks. Results from this study suggest that interventions directed at reducing the contamination on farm worker hands would be effective at interrupting the transmission of foodborne pathogens to produce.