title: Effects of antimicrobials fed as dietary growth promoters on faecal shedding of Campylobacter, Salmonella and shiga-toxin producing Escherichia coli in swine.
abstract: OBJECTIVE
  To determine whether antimicrobials commonly used in swine diets affect zoonotic pathogen shedding in faeces.
  
  
  RESULTS
  Barrows (n = 160) were sorted into two treatments at 10 weeks of age (week 0 of the study), and fed growing, grow finishing and finishing diets in 4-week feeding periods. For each feeding phase, diets were prepared without (A-) and with (A+) dietary antimicrobials (chlortetracycline, 0-8 week; bacitracin, 9-12 week) typical of the United States. At week 0, 4, 8, 9, 10 and 12 of the study, faecal swabs or grabs were collected for analyses. Campylobacter spp. was absent at week 0, but prevalence increased over time with most isolates being identified as Campylobacter coli. When chlortetracycline was used in A+ diets (week 4 and 8), prevalence for Campylobacter spp., pathogenic Escherichia coli O26 and stx genes was lower in faeces. On week 12 after the shift to bacitracin, Campylobacter spp. and stx genes were higher in faeces from piglets fed A+ diet. Pathogenic E. coli serogroups O103 and O145 were isolated throughout the study and their prevalence did not differ due to diet. Pathogenic E. coli serogroups O111 and O121 were never found in the piglets, and Salmonella spp. prevalence was low.
  
  
  CONCLUSIONS
  In production swine, growing diets with chlortetracycline may have reduced pathogen shedding compared with the A-growing diets, whereas finishing diets with bacitracin may have increased pathogen shedding compared with the A-finishing diet.
  
  
  CONCLUSIONS
  Inclusion of antimicrobials in the diet can affect zoonotic pathogen shedding in faeces of swine.
authors.affiliation: USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA. jim.wells@ars.usda.gov
authors.forename: J E
authors.initials: JE
authors.lastname: Wells
authors.forename: N
authors.initials: N
authors.lastname: Kalchayanand
authors.forename: E D
authors.initials: ED
authors.lastname: Berry
authors.forename: W T
authors.initials: WT
authors.lastname: Oliver
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001419:Bacteria / Q000302:isolation & purification*; D057138:Bacterial Shedding / Q000187:drug effects*; D002167:Campylobacter / Q000302:isolation & purification; D004032:Diet; D019587:Dietary Supplements; D005243:Feces / Q000382:microbiology; D012475:Salmonella / Q000302:isolation & purification; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification; D013552:Swine / Q000254:growth & development / Q000382:microbiology*
chemical_list: D000890:Anti-Infective Agents