Contamination of fresh produce by microbial indicators on farms and in packing facilities: Elucidation of environmental routes

• Type of Material: Article
• Authors: Faith E. Bartz, Emory University; Jacquelyn Sunshine Lickness, Emory University; Norma Heredia, Universidad Autonoma de Nuevo Leon; Anne Fabiszewski de Aceituno, Emory University; Kira L. Newman, Emory University; Domonique Watson Hodge, Emory University; Lee-Ann Jaykus, North Carolina State University; Santos García, Universidad Autonoma de Nuevo Leon; Juan Leon, Emory University
• Language: English
• Date: 2017-06-01
• Publisher: American Society for Microbiology
• Publication Version: Final Published Version
• Copyright Statement: © 2017 American Society for Microbiology.
• Final Published Version (URL): http://dx.doi.org/10.1128/AEM.02984-16
• Title of Journal or Parent Work: Applied and Environmental Microbiology
• ISSN: 0099-2240
• Volume: 83
• Issue: 11
• Grant/Funding Information: This work was partially supported by the Emory University Global Health Institute.; This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award numbers 2010-85212-20608, 2011-67012-30762, and 2015-67017-23080.
• Keywords: produce; food-borne pathogens; environmental microbiology
• Research Categories: Health Sciences, General; Health Sciences, Epidemiology; Health Sciences, Public Health

Abstract

To improve food safety on farms, it is critical to quantify the impact of environmental microbial contamination sources on fresh produce. However, studies are hampered by difficulties achieving study designs with powered sample sizes to elucidate relationships between environmental and produce contamination. Our goal was to quantify, in the agricultural production environment, the relationship between microbial contamination on hands, soil, and water and contamination on fresh produce. In 11 farms and packing facilities in northern Mexico, we applied a matched study design: composite samples (n = 636, equivalent to 11,046 units) of produce rinses were matched to water, soil, and worker hand rinses during two growing seasons. Microbial indicators (coliforms, Escherichia coli, Enterococcus spp., and somatic coliphage) were quantified from composite samples. Statistical measures of association and correlations were calculated through Spearman's correlation, linear regression, and logistic regression models. The concentrations of all microbial indicators were positively correlated between produce and hands (ρ range, 0.41 to 0.75; P < 0.01). When E. coli was present on hands, the handled produce was nine t imes more likely to contain E. coli (P < 0.05). Similarly, when coliphage was present on hands, the handled produce was eight times more likely to contain coliphage (P < 0.05). There were relatively low concentrations of indicators in soil and water samples, and a few sporadic significant associations were observed between contamination of soil and water and contamination of produce. This methodology provides a foundation for future field studies, and results highlight the need for interventions surrounding farmworker hygiene and sanitation to reduce microbial contamination of farmworkers' hands.