Antimicrobial resistance markers of class 1 and class 2 integron-bearing Escherichia coli from irrigation water and sediments

Emerg Infect Dis. 2003 Jul;9(7):822-6. doi: 10.3201/eid0907.020529.


Municipal and agricultural pollution affects the Rio Grande, a river that separates the United States from Mexico. Three hundred and twenty-two Escherichia coli isolates were examined for multiple antibiotic resistance phenotypes and the prevalence of class 1 and class 2 integron sequences. Thirty-two (10%) of the isolates were resistant to multiple antibiotics. Four (13%) of these isolates contained class 1-specific integron sequences; one isolate contained class 2 integron-specific sequences. Sequencing showed that the class 1 integron-bearing strain contained two distinct gene cassettes, sat-1 and aadA. Although three of the four class 1 integron-bearing strains harbored the aadA sequence, none of the strains was phenotypically resistant to streptomycin. These results suggest that integron-bearing E. coli strains can be present in contaminated irrigation canals and that these isolates may not express these resistance markers.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Drug Resistance, Bacterial / genetics*
  • Escherichia coli / drug effects
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification*
  • Genetic Markers
  • Geologic Sediments / microbiology*
  • Integrons / genetics*
  • Phenotype
  • Water Microbiology*


  • Anti-Bacterial Agents
  • Genetic Markers