Prevalence of Campylobacter in Integrated Mixed Crop-livestock Farms and Its Survival Ability in Post-harvest Products

Introduction: Products from Mixed Crop-Livestock Farms (MCLFs) are commonly sold in farmers markets or road-side shops. Regulating the microbiological quality of these products is difficult because most small farm operations that commonly sell their products at farmers markets are exempt from USDA scrutiny under the Food Safety Modernization Act. Campylobacter, one of the most common causative agents of acute gastroenteritis, can contaminate these products. 

Purpose: The purpose of this study was to investigate the ecological distribution of Campylobacter in MCLF environment and their products compared to conventional farms and their products at pre- and post-harvest level.

Methods: A total of 1287 samples at pre-harvest level and 1,281 samples at post-harvest level were collected from Maryland and the DC metropolitan area. Campylobacter was identified with biochemical tests and PCR. Antibiotic resistance of the isolates was determined with agar dilution method.

Results: A total of 222 Campylobacter isolates were identified. Campylobacter was detected in 11.16% and 3.6% of MCLFs and conventional farm samples, respectively, but none from produce-only farm samples. Antibiotic resistance was 2 - 3 times higher in conventional farms compared to MCLF isolates except tetracycline resistance, which was observed in 51.02% of MCLFs but none in conventional farm isolates. At post-harvest level, Campylobacter was isolated in 87.5%, 71.43% and 33.33% of whole chicken carcasses in farmers markets, organic and conventional retail supermarkets, respectively. Tetracycline resistance was found > 3 times higher in organic poultry meat isolates compared to conventional counterparts. No Campylobacter was detected in post-harvest produce samples due in part to the disability of Campylobacter to survive in absence of sufficient water activity.

Significance: This study reveals the higher risks of the MCLF environment and their products that are sold in retail and farmers markets. Higher tetracycline resistance in MCLF environment, farmers market and organic poultry carcass isolates warrants further investigation.