206: Occurrence, AMR Patterns, and Genomic Diversity of Microbes in Farmers' Market Food Commodities in Central Virginia Before and During the COVID-19 Pandemic

Introduction

Given the positive correlation between the rise in farmers' markets and foodborne illness cases, it is crucial to assess the impact of PPE use during the COVID-19 pandemic on food microbial quality.

Methods

This study investigated the occurrence, antimicrobial resistance (AMR), and genomic diversity of bacteria in 740 food samples from 76 farm operations sold at 15 farmers' markets in Central Virginia between August 2020 and December 2021.

Results

Campylobacter, E. coli, Listeria, and Salmonella were detected in the samples at 1.5%, 19.2%, 7.3%, and 0.8% during the pandemic. Compared to the previous findings between March and November 2017 (pre-pandemic), Campylobacter and Listeria prevalence decreased by about 3.6% and 5.5%, while E. coli and Salmonella increased by 1.7% and 0.3%. Among bacterial isolates from the pandemic period, resistance to ampicillin (AMP), streptomycin (STR), nalidixic acid (NAL), and amoxicillin-clavulanic acid was most common, found in 90.9% of Campylobacter, 50.4% E. coli, 90.9% Listeria, and 66.7% Salmonella isolates, respectively. Across all 387 bacterial species tested, STR was identified to be the least effective, with 88.4% non-susceptibility, while sulfamethoxazole-trimethoprim (SXT) was the most effective, showing 99.5% susceptibility. Overall, about 7% exhibited multidrug resistance (MDR). For the isolates obtained before the pandemic, non-susceptibility to AMP, AMP, and NAL was most common, found in 100% Campylobacter, 62.4% E. coli, and 86.7% Listeria, respectively. Across all 203 bacterial species tested, AMP was identified to be the least effective, with 61.1% non-susceptibility, while SXT was the most effective, showing 88.1% susceptibility. Overall, about 32% exhibited MDR. Regardless of pre- and during the pandemic, none of the tested antimicrobials was universally effective against all bacterial species. No E. coli isolates obtained from food commodities had matching pulsed-field gel electrophoresis (PFGE) profiles, indicating the bacteria's sample and market specificity and genomic diversity.

Significance

Despite compliance with PPE protocols by vendors and consumers during the pandemic, foodborne pathogens with AMR continue to be detected in food commodities, highlighting the importance of ongoing research and education to address these issues and promote the safe development of farmers' markets.

Authors: Chyer Kim, Abeer Abujamous, Theresa Nartea, Allissa Riley, Salina Parveen, Junglim Lee, Ramesh Dhakal, Eunice Ndegwa, and Daria Clinkscales