Prevalence and genomic characterization of Escherichia coli O157: H7 in cow-calf herds throughout California

Jay N. Worley, Kristopher A. Flores, Xun Yang, Jennifer A. Chase, Guojie Cao, Shuai Tang, Jianghong Meng, Edward R. Atwill

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Escherichia coli serotype O157:H7 is a zoonotic food- and waterborne bacterial pathogen that causes a high hospitalization rate and can cause lifethreatening complications. Increasingly, E. coli O157:H7 infections appear to originate from fresh produce. Ruminants, such as cattle, are a prominent reservoir of E. coli O157:H7 in the United States. California is one of the most agriculturally productive regions in the world for fresh produce, beef, and milk. The close proximity of fresh produce and cattle presents food safety challenges on a uniquely large scale. We performed a survey of E. coli O157:H7 on 20 farms in California to observe the regional diversity and prevalence of E. coli O157:H7. Isolates were obtained from enrichment cultures of cow feces. Some farms were sampled on two dates. Genomes from isolates were sequenced to determine their relatedness and pathogenic potential. E. coli O157:H7 was isolated from approximately half of the farms. The point prevalence of E. coli O157:H7 on farms was highly variable, ranging from zero to nearly 90%. Within farms, generally one or a few lineages were found, even when the rate of isolation was high. On farms with high isolation rates, a single clonal lineage accounted for most of the isolates. Farms that were visited months after the first visit might have had the same lineages of E. coli O157:H7. Strains of E. coli O157:H7 may be persistent for months on farms.

Original languageEnglish (US)
Article numbere00734-17
JournalApplied and Environmental Microbiology
Issue number16
StatePublished - Aug 1 2017
Externally publishedYes


  • California
  • Cattle
  • Escherichia coli
  • Food-borne pathogens
  • Genomics
  • O157:H7
  • STEC

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


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