Purpose: To assess the microbiological safety and quality of produce, beef, and pork obtained from farmers’ markets in Pennsylvania through the enumeration of hygiene indicators and screening of E. coli isolates for select virulence genes and phylogenetic profiling.
Methods: Coliforms, fecal coliforms, and E. coli were enumerated from produce (n=150) and meat (n=50) obtained from farmers’ markets in Pennsylvania, using the Most Probable Number method. Listeria spp. presence was determined using Biomerieux’s Vidas system. Phylogenetic analysis of E. coli was performed using the Clermont method, and isolates were screened for Shiga toxin-producing (STEC)- and Extra-intestinal pathogenic E. coli (ExPEC)-associated genes using multiplex PCR.
Results: E. coli was isolated from 40% (20/50) and 18% (9/50) of beef and pork, and found in 28% (15/54), 29% (15/52), and 17% (8/46) of kale, lettuce, and spinach, respectively. Listeria spp. was isolated from beef (8%; 4/50), kale (2%; 1/54), lettuce (4%; 2/52), and spinach (7%; 3/46), with three isolates confirmed as L. monocytogenes. E. coli isolated from meat mainly clustered into phylogroup B1 (66%; 19/29), while produce isolates primarily clustered into phylogroups B2 (36%; 14/39) and B1 (33%; 13/39). ExPEC/STEC-associated genes present in E. coli (n=67) included: fimH (100%; 67/67) iroN (3%; 2/67), hlyD (3%; 2/67), and eae (1.5%; 1/67).
Significance: The presence of Listeria spp. and E. coli on farmers’ market produce and meat are strong indicators that the practices of vendors have a serious impact on the safety of the foods they sell. Farmers’ market vendors may benefit from food safety training and increased public health oversight.