title: Antimicrobial Resistance Profiles in Escherichia coli O157 Isolates from Northern Colorado Dairies.
abstract: Escherichia coli O157 (EcO157) infections can lead to serious disease and death in humans. Although the ecology of EcO157 is complex, ruminant animals serve as an important reservoir for human infection. Dairy cattle are unique because they may be a source of contamination for milk, meat, and manure-fertilized crops. Foodborne dairy pathogens such as EcO157 are of primary importance to public health. Antimicrobial resistance (AMR) is a complex phenomenon that complicates the treatment of serious bacterial infections and is of increasing concern. In the face of recommended use restrictions for antimicrobial agents in livestock operations, current AMR patterns in known foodborne pathogens should be documented. The objective of this study was to document AMR patterns in EcO157 isolates from dairies in northern Colorado using antimicrobial agents commonly found on dairies and representative of medically important antimicrobial drug classes. Seventy-five EcO157 isolates were recovered from three dairies. Six isolates were resistant to at least 1 of the 10 tested antimicrobial agents: four were resistant to streptomycin, sulfisoxazole, and tetracycline; one was resistant to streptomycin and tetracycline; and one was resistant to only tetracycline. All resistant isolates were from a single dairy. Overall, a low prevalence (8%) of AMR was observed among the 75 EcO157 isolates. No significant effects on AMR profiles due to virulence genes, parity, or previous antimicrobial treatments within the current lactation period were detected. The results of this study provide background information for future comparative studies investigating AMR trends. Future studies should include more participating farms and more samples and should control for potential confounding factors of AMR that may underlie individual farm variation.
authors.affiliation: Department of Clinical Sciences, Colorado Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA. craig.mcconnel@colostate.edu.
authors.forename: Craig S
authors.initials: CS
authors.lastname: McConnel
authors.affiliation: Department of Clinical Sciences, Colorado Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Chloe M
authors.initials: CM
authors.lastname: Stenkamp-Strahm
authors.affiliation: Department of Clinical Sciences, Colorado Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Rao
authors.affiliation: Department of Clinical Sciences, Colorado Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Lyndsey M
authors.initials: LM
authors.lastname: Linke
authors.affiliation: Department of Clinical Sciences, Colorado Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Roberta J
authors.initials: RJ
authors.lastname: Magnuson
authors.affiliation: Department of Microbiology, Immunology and Pathology, Colorado Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Doreene R
authors.initials: DR
authors.lastname: Hyatt
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002511:Cephalosporins / Q000494:pharmacology; D003120:Colorado; D003612:Dairying; D024901:Drug Resistance, Multiple, Bacterial; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000662:veterinary; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000302:isolation & purification*; D024841:Fluoroquinolones / Q000494:pharmacology; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D008892:Milk / Q000382:microbiology; D010406:Penicillins / Q000494:pharmacology; D000069466:Red Meat / Q000382:microbiology; D013449:Sulfonamides / Q000494:pharmacology; D013754:Tetracyclines / Q000494:pharmacology; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D024841:Fluoroquinolones; D010406:Penicillins; D013449:Sulfonamides; D013754:Tetracyclines; D015662:Trimethoprim, Sulfamethoxazole Drug Combination