title: Prevalence and antimicrobial susceptibility of virulent and avirulent multidrug-resistant Escherichia coli isolated from diarrheic neonatal calves.
abstract: OBJECTIVE
  To determine the prevalence of selected virulence genes and the antimicrobial susceptibility of multidrug-resistant (MDR) Escherichia coli isolated from diarrheic neonatal calves.
  
  
  METHODS
  97 E coli isolates from diarrheic neonatal calves.
  
  
  METHODS
  E coli isolates were tested via PCR assay for 6 virulence genes and susceptibility to 17 drugs belonging to 9 classes. A 2-sample test of proportions was used to make comparisons between proportions of virulent and avirulent MDR isolates.
  
  
  RESULTS
  23 of 97 (23.7%) isolates were virulent, and 74 (76.3%) were avirulent. Of the 23 virulent isolates, 15 (65.2%) were positive for K99, 14 (60.9%) for F41, 12 (52.2%) for STa, 9 (39.1%) for Stx1, 6 (26.1%) for intimin, and 0 (0%) for Stx2. Twenty of 23 (87.0%) virulent isolates expressed ≥ 2 virulence genes, and 3 of 23 (13.0%) were positive for 1 virulence factor. Eight of 23 (34.8%) virulent isolates expressed STa, K99, and F41, whereas 1 of 23 (4.4%) was positive for STa, F41, intimin, and Stx1. The second most frequent gene pattern was Stx1 and intimin. Twenty of 23 (87.0%) virulent isolates were MDR; the highest prevalence of resistance was recorded for the macrolide-lincosides, followed by the tetracyclines and penicillins. Also, 17 of 23 (74.0%) virulent isolates were resistant to sulfadimethoxine, and 10 of 23 (43.5%) were resistant to trimethoprim-sulfamethoxazole. Additionally, 60 of 74 (81.0%) avirulent isolates were MDR.
  
  
  CONCLUSIONS
  The prevalence of multidrug resistance was comparable for virulent and avirulent E coli isolated from diarrheic neonatal calves. Cephalosporins and aminoglycosides had reasonable susceptibility.
authors.affiliation: Department of Veterinary and Microbiological Sciences, College of Agriculture, Food Systems, and Natural Resources, North Dakota State University, Fargo, ND 58108, USA. Robert.Barigye@nt.gov.au
authors.forename: Robert
authors.initials: R
authors.lastname: Barigye
authors.forename: Ablesh
authors.initials: A
authors.lastname: Gautam
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Piche
authors.forename: Lynn P
authors.initials: LP
authors.lastname: Schaan
authors.forename: Darlene F
authors.initials: DF
authors.lastname: Krogh
authors.forename: Susan
authors.initials: S
authors.lastname: Olet
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000382:microbiology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D008910:Minnesota / Q000453:epidemiology; D060885:Multiplex Polymerase Chain Reaction / Q000662:veterinary; D009658:North Dakota / Q000453:epidemiology; D015995:Prevalence; D013023:South Dakota / Q000453:epidemiology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D037521:Virulence Factors