Purpose: The objective of this study was to evaluate the occurrence of STEC in small-sized cattle farms in Arkansas Delta Region.
Methods: Rectal Swabs and environmental samples including soil, feed and water were collected from 21 farms in five counties in Northeast Arkansas over 12 months and analyzed for the presence of STEC. Each farm was visited twice (warm spring and colder fall-winter season). Presence of STEC was analyzed by selective culture method using rainbow agar and multiplex PCR for stx 1/2 genes and rfb gene for O157 serotype.
Results: The overall STEC prevalence in beef cattle farms was 59.1%; however, the STEC prevalence rate greatly varied in each farm from 0% to 76.9%. Non-O157 STEC was more prevalent (49.9%) than O157 STEC (21.2%) in rectal swabs from beef cattle but O157 STEC was more prevalent (47%) in environmental sample than non-O157 STEC (7.6%). No significant correlation was found between STEC prevalence and season or the farm location. In addition, the prevalence of STEC in beef cattle was not correlated to any of the environmental factors. The results from this study indicate a high occurrence of non-O157 STEC in small-sized beef cattle farms and it might have different transmission mechanism than E. coli O157:H7. The results also suggest more research needs to be done to better understand the potential reservoirs of non-O157 STEC and develop pre-harvest risk management strategies.
Significance: This was the first study focusing on prevalence of STEC in small-sized cattle farms, and knowledge obtained from this research will ultimately improve food safety by significantly reducing beef-associated human STEC infections.