To compare microbiological indicator and pathogen contamination among different types of fresh produce and environmental samples along the production chain, 636 samples of produce (rinsates from cantaloupe melons, jalapeño peppers, and tomatoes) and environmental samples (rinsates from hands of workers, soil, and water) were collected at four successive steps in the production process (from the field before harvest through the packing facility) on 11 farms in northern Mexico during 2011 and 2012. Samples were assayed for enteric pathogens (Escherichia coli O157:H7, other Shiga toxigenic E. coli, Salmonella, and Listeria monocytogenes) and microbial indicators (coliforms, other E. coli strains, and Enterococcus spp.). Salmonella was the only pathogen detected; it was found in one preharvest jalapeño sample (detection limits: 0.0033 CFU/ml in produce and hand samples, 0.0013 CFU/ml in water, and 0.04 CFU/g in soil). Microbial indicator profiles for produce, worker hands, and soil from jalapeño and tomato farms were similar, but cantaloupe farm samples had higher indicator levels (P < 0.05 for all comparisons) on fruit (6.5, 2.8, and 7.2 log CFU per fruit) and hands (6.6, 3.1, and 7.1 log CFU per hand) for coliforms, E. coli, and Enterococcus, respectively, and lower E. coli levels in soil (<1 CFU/g). In water from tomato farms, E. coli indicators were significantly more prevalent (70 to 89% of samples were positive; P = 0.01 to 0.02), and geometric mean levels were higher (0.3 to 0.6 log CFU/100 ml) than those in cantaloupe farm water (32 to 38% of samples were positive, geometric mean <1 CFU/100 ml). Microbial indicators were present during all production steps, but prevalence and levels were generally highest at the final on-farm production step (the packing facility) (P < 0.03 for significant comparisons). The finding that microbial contamination on produce farms is influenced by produce type and production step can inform the design of effective approaches to mitigate microbial contamination.
Bibliographical noteFunding Information:
This material is based upon work that was supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under awards 2010-85212-20608, 2011-67012-30762, and 2015-67017-23080. The authors thank the produce growers and farm workers who participated in the study. We also acknowledge the members of our scientific and community advisory boards: Elizabeth Bihn, James Gorny, John (Jack) Guzewich, Robert Mandrell, José Luis Rodríguez Cavazos, José Elías Treviño Ramírez, and Lorenzo J. Maldonado Aguirre. The authors also thank Drs. Trevor Suslow, Robert Gravani, Robert Atwill, and Cristobal Chaidez for input on sampling and assay methods; and Elizabeth Adam, Gaelle Gourmelon, Yiru Lily Gu, Neha Kamat, Jacquelyn Sunshine Lickness, Valerie Morrill, Alice Parish, Domonique Watson Hodge, Denis Whelan, and Laura Wright for assistance with data management and analysis.
Copyright ©, International Association for Food Protection.
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)