title: Fecal shedding of, antimicrobial resistance in, and serologic response to Salmonella Typhimurium in dairy calves.
abstract: OBJECTIVE
  To determine the duration of fecal shedding of and serologic response to Salmonella spp after natural infection in dairy calves and characterize Salmonella organisms recovered from these herds.
  
  
  METHODS
  Longitudinal study.
  
  
  METHODS
  Calves from 2 dairy herds (A and B) in the northeast United States that were identified at the beginning of a Salmonella outbreak.
  
  
  METHODS
  Fecal samples were collected twice per week (herd A) or once per week (herd B); blood samples were collected for serologic testing once per week in both herds. Bacteriologic culture of fecal samples was performed, and Salmonella isolates were characterized by serotype, pulsed-field gel electrophoresis (PFGE) pattern, and antimicrobial resistance profile.
  
  
  RESULTS
  All Salmonella isolates from herd A were serovar Typhimurium var Copenhagen, had the same PFGE pattern, and were resistant to at least 9 antimicrobials. All isolates from herd B were Salmonella Typhimurium, represented 2 PFGE patterns, and were susceptible to all antimicrobials evaluated. The estimated duration of fecal shedding was 14 days in herd A and 9 days in herd B. Few calves were seropositive for antibody against Salmonella lipopolysaccharide within the first week after birth (0 of 20 in herd A and 13 of 79 in herd B) or seroconverted (6 in herd A and 4 in herd B). Fecal shedding was more common in calves that seroconverted, but overall, there was not a strong association between seropositivity and fecal shedding of Salmonella organisms.
  
  
  CONCLUSIONS
  Although the herds differed in serologic response and Salmonella subtype, the duration of fecal shedding among calves was similar between herds.
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Alexander
authors.forename: Lorin D
authors.initials: LD
authors.lastname: Warnick
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Cripps
authors.forename: Patrick L
authors.initials: PL
authors.lastname: McDonough
authors.forename: Yrjo T
authors.initials: YT
authors.lastname: Grohn
authors.forename: Martin
authors.initials: M
authors.lastname: Wiedmann
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Reed
authors.forename: Karen L
authors.initials: KL
authors.lastname: James
authors.forename: Yesim
authors.initials: Y
authors.lastname: Soyer
authors.forename: Renata
authors.initials: R
authors.lastname: Ivanek
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D003612:Dairying; D024901:Drug Resistance, Multiple, Bacterial; D005243:Feces / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents