Antibiotic-resistant E. Coli in surface water and groundwater in dairy operations in Northern California

Xunde Li, Naoko Watanabe, Chengling Xiao, Thomas Harter, Brenda Mccowan, Yingjia Liu, Edward R Atwill

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Generic Escherichia coli was isolated from surface water and groundwater samples from two dairies in Northern California and tested for susceptibility to antibiotics. Surface samples were collected from flush water, lagoon water, and manure solids, and groundwater samples were collected from monitoring wells. Although E. coli was ubiquitous in surface samples with concentrations ranging from several hundred thousand to over a million colony-forming units per 100 mL of surface water or per gram of surface solids, groundwater under the influence of these high surface microbial loadings had substantially fewer bacteria (3- to 7-log10 reduction). Among 80 isolates of E. coli tested, 34 (42.5 %) were resistant to one or more antibiotics and 22 (27.5 %) were multi-antibiotic resistant (resistant to ≥3 antibiotics), with resistance to tetracycline, cefoxitin, amoxicillin/clavulanic acid, and ampicillin being the most common. E. coli isolates from the calf hutch area exhibited the highest levels of multi-antibiotic resistance, much higher than isolates in surface soil solids from heifer and cow pens, flush alleys, manure storage lagoons, and irrigated fields. Among E. coli isolates from four groundwater samples, only one sample exhibited resistance to ceftriaxone, chloramphenicol, and tetracycline, indicating the potential of groundwater contamination with antibiotic-resistant bacteria from dairy operations.

Original languageEnglish (US)
Pages (from-to)1253-1260
Number of pages8
JournalEnvironmental Monitoring and Assessment
Issue number2
StatePublished - Feb 2014


  • Antibiotic resistance
  • Dairy
  • E. coli
  • Water

ASJC Scopus subject areas

  • Environmental Science(all)
  • Management, Monitoring, Policy and Law
  • Pollution


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