title: Factor analysis of minimum-inhibitory concentrations for Escherichia coli isolated from feedlot cattle to model relationships among antimicrobial-resistance outcomes.
abstract: Factor analysis was used to assess relationships in the minimum-inhibitory concentration among 17 antimicrobials tested on isolates of Escherichia coli isolated from 360 faecal samples obtained from feedlot cattle. Six factors were extracted using maximum-likelihood factor analysis. The factors were interpretable antimicrobial groupings based on class of antimicrobial and previously described associations. New-generation cephalosporins, older-generation beta-lactams, fluoroquinolones and aminoglycosides grouped separately as classes of antimicrobials on four of the six factors. One of the remaining factors was a grouping of antimicrobials that had been identified as being related in previous feedlot studies. The last factor was a grouping of three of the five antimicrobials that comprise the antimicrobials found in penta-resistant strains of Salmonella Typhimurium. The factor analysis described patterns in the MIC data that would not have been apparent if only antimicrobial-resistance data categorized as susceptible-resistance had been analysed.
authors.affiliation: Centers for Epidemiology and Animal Health, US Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services, CO 80526-8117, USA. bruce.a.wagner@aphis.usda.gov
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Wagner
authors.forename: Mo D
authors.initials: MD
authors.lastname: Salman
authors.forename: David A
authors.initials: DA
authors.lastname: Dargatz
authors.forename: Paul S
authors.initials: PS
authors.lastname: Morley
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wittum
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Keefe
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D024881:Drug Resistance, Bacterial / Q000502:physiology; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology*; D005163:Factor Analysis, Statistical; D005243:Feces / Q000382:microbiology; D008297:Male; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D015233:Models, Statistical
chemical_list: D000900:Anti-Bacterial Agents