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P2-63 Monophyletic E. coli O157:H7 Population Spikes in Cattle Herds Observed in California’s Central Valley

Tuesday, August 2, 2016
America's Center - St. Louis
Jay Worley, University of Maryland, College Park, MD
Guojie Cao, University of Maryland, College Park, MD
Jennifer Chase, University of California-Davis, Davis, CA
Kristopher Flores, University of California-Davis, Davis, CA
Xun Yang, University of Maryland, College Park, MD
Shuai Tang, University of Maryland, College Park, MD
Marc Allard, U.S. Food and Drug Administration-CFSAN, College Park, MD
Eric Brown, U.S. Food and Drug Administration-CFSAN, College Park, MD
Edward Atwill, University of California-Davis, Davis, CA
Jianghong Meng, University of Maryland, College Park, MD
Introduction: Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen capable of causing life-threatening disease. In particular, serotype O157:H7 is associated with disease complications. Ruminants, such as cattle, are a natural reservoir of the pathogen and large herds of cattle are located near fields used to grow crops for raw consumption across the U.S., which presents potential public health risks.

Purpose: To gain insight into O157:H7 population diversity and dynamics, we performed a survey of 20 herds across California’s Central Valley. This information is important for both molecular epidemiology and food-safety protocols, particularly regarding slaughter and harvest.

Methods: The survey of cattle was performed by obtaining isolates from individual fecal samples in 20 herds, around 40 samples per visit. Genome sequences were obtained using next-generation sequencing (Illumina MiSeq).

Results: A total of 39 herd visits were made, and 12 visits returned with samples positive for O157:H7. These 12 visits were from 9 of 20 herds visited and produced 85 O157:H7 isolates. E. coli O157:H7 isolates from herds with a high rate of isolation (>30%) had a single monophyletic lineage to which most isolates belonged. A follow-up survey from one of the farms that had a high isolation rate (87.5%), performed 11 months later, showed a highly reduced O157:H7 isolation rate (5.2%). The formerly highly prevalent lineage, however, was still present. Most of the isolates were genetically similar to clinical isolates from known O157:H7 outbreaks.

Significance: Cattle herds may go through temporary periods where O157:H7 is shed at a high prevalence throughout the population, meaning that these times, if avoided for slaughter or harvest in downstream fields, could lead to reduced risks of contamination with the pathogen. O157:H7 strains with the potential to cause severe disease are present in many herds in California’s Central Valley.

Back to: Poster Session 2 – Low-water Activity, Laboratory and Detection Methods, Epidemiology, Produce, Pre-harvest, Dairy and Beverages, Food Defense, General Microbiology
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