title: Clinical sensitivity and specificity of a real-time PCR assay for Campylobacter fetus subsp venerealis in preputial samples from bulls.
abstract: OBJECTIVE
  To determine clinical sensitivity and specificity of a quantitative real-time PCR (qRT-PCR) assay for Campylobacter fetus subsp venerealis (Cfv) in preputial samples of bulls.
  
  
  METHODS
  313 beef bulls.
  
  
  METHODS
  Preputial samples were collected from 300 virgin bulls and 13 Cfv-infected bulls. Specificity of the qRT-PCR assay, determined on the basis of results for samples collected from virgin bulls, was compared with specificity of bacteriologic culture performed with transport enrichment medium (TEM). Sensitivity of the qRT-PCR assay, determined on the basis of results for multiple samples collected at weekly intervals from infected bulls, was compared with sensitivity of the direct fluorescent antibody test (DFAT), bacteriologic culture, and bacteriologic culture with TEM.
  
  
  RESULTS
  Specificity was 85% for the qRT-PCR assay and 100% for bacteriologic culture; results were significantly different. Mean sensitivity was 85.4% for the qRT-PCR assay, 82.3% for direct culture in blood agar, 72.1% for the DFAT, 32.7% for direct culture in Skirrow agar, 30% for bacteriologic culture with TEM and blood agar, and 38.1% for bacteriologic culture with TEM and Skirrow agar. Differences in sensitivity among tests varied with ambient outdoor temperature. Repeated sampling significantly increased sensitivity of the qRT-PCR assay.
  
  
  CONCLUSIONS
  Use of the qRT-PCR assay as a screening test on direct preputial samples had comparable sensitivity to bacteriologic culture, and repeated sampling improved sensitivity. Although improved performance of the qRT-PCR assay, compared with direct bacteriologic culture, was dependent on temperature, transport times that allow direct culture are unlikely under field conditions. The qRT-PCR assay would provide a fast and sensitive screening method for Cfv in bulls.
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Alvaro García
authors.initials: AG
authors.lastname: Guerra
authors.forename: Bonnie
authors.initials: B
authors.lastname: Chaban
authors.forename: Janet E
authors.initials: JE
authors.lastname: Hill
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Waldner
authors.forename: Steven H
authors.initials: SH
authors.lastname: Hendrick
mesh_terms: D000818:Animals; D002169:Campylobacter Infections / Q000175:diagnosis / Q000382:microbiology / Q000662:veterinary*; D002168:Campylobacter fetus / Q000302:isolation & purification*; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis / Q000382:microbiology*; D003470:Culture Media; D008297:Male; D060888:Real-Time Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods; D013696:Temperature
chemical_list: D003470:Culture Media