Somatic Coliphage Profiles of Produce and Environmental Samples from Farms in Northern México

Abstract

Somatic coliphages were quantified in 459 produce and environmental samples from 11 farms in Northern Mexico to compare amounts of somatic coliphages among different types of fresh produce and environmental samples across the production steps on farms. Rinsates from cantaloupe melons, jalapeño peppers, tomatoes, and the hands of workers, soil, and water were collected during 2011-2012 at four successive steps on each farm, from the field before harvest through the packing facility, and assayed by FastPhage MPN Quanti-tray method. Cantaloupe farm samples contained more coliphages than jalapeño or tomato (p range <0.01-0.03). Across production steps, jalapeños had higher coliphage percentages before harvest than during packing (p = 0.03), while tomatoes had higher coliphage concentrations at packing than all preceding production steps (p range <0.01-0.02). These findings support the use of targeted produce-specific interventions at multiple points in the process of growing and packing produce to reduce the risk of enteric virus contamination and improve food safety during fruit and vegetable production.

Contamination of Fresh Produce by Microbial Indicators on Farms and in Packing Facilities: Elucidation of Environmental Routes

“…However, as noted in our previous studies (27,28), the distributions of these four microbial indicators differed, and these had implications for the statistical analysis. The low rate of detection of E. coli was useful for logistic regression analyses.…”

“…Bacterial indicators were assayed by enumerative methods on selective media, and coliphages were detected by using the Fast Phage most probable number (MPN) Quanti-Tray method (Charm Sciences, Lawrence, MA) (27,28). The concentration of each bacterial indicator per sample was based on the combined replicate plate counts of CFU and effective sample volumes according to a U.S. Food and Drug Administration (FDA) methodology (53).…”

“…This may be due to logistical constraints in setting up a matched study design (6,17), resource constraints in acquiring large sample sizes (18), application of the appropriate statistical analyses to account for multivariable factors affecting microbial contamination (6,(19)(20)(21), and data variability from diverse microbial distributions on produce and environmental samples (22)(23)(24). Because of the low rate of detection of pathogen contamination (25)(26)(27)(28), populations of microbial-indicator organisms, including organisms that indicate filth (coliforms) and/or fecal contamination (Escherichia coli, Enterococcus spp., and somatic coliphage), can be monitored (reviewed in references 29 to 31).…”

“…Our previous studies (6,27,28) quantified microbial indicators and pathogen contamination among fresh produce and environmental samples during the production chain. However, neither these studies nor any others to date have quantitatively compared the direct impacts of microbial contamination of hands, soil, water, or surfaces on fresh produce in the agricultural environment.…”