Species characterization and minimum inhibitory concentration patterns of brachyspira species isolates from swine with clinical disease

Kristin A Clothier, Joann M. Kinyon, Timothy S. Frana, Nadine Naberhaus, Leslie Bower, Erin L. Strait, Kent Schwartz

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Typhlocolitis and dysentery due to Brachyspira hyodysenteriae infection represent an economically important disease syndrome in growing pigs. Largely disappearing from U.S. swine herds in the late 1990s and early 2000s, Brachyspira-associated disease and bacterial isolation from swine with clinical disease has increased in the last several years, and non-B. hyodysenteriae isolates are commonly identified. Antimicrobial resistance has been demonstrated in Brachyspira spp. isolates from Europe and Asia, and may be the reason for the resurgence in U.S. herds. Seventy-nine clinical isolates identified at the Iowa State University Veterinary Diagnostic Lab were tested with multiple polymerase chain reaction assays to establish species identity, and evaluated for minimum inhibitory concentrations (MICs) using an agar dilution method against lincomycin, gentamicin, valnemulin, tiamulin, salinomycin, and carbadox. Only 38.0% of isolates could be confirmed as the known pathogens B. hyodysenteriae (30.4%) or Brachyspira pilosicoli (7.6%). Twenty of the 79 isolates (25.3%) were identified as Brachyspira murdochii, and 13.9% could not be identified to species. The MIC values were consistently high against lincomycin and moderately high against gentamicin. The remaining antimicrobials had MICs that were at the low end of the test ranges. Brachyspira murdochii and Brachyspira spp. had significantly greater MIC values against several of these drugs than other Brachyspira spp. examined. The increased incidence of these less definitively characterized Brachyspira species with increased MIC values to commonly prescribed antimicrobials may, at least in part, explain the increased prevalence and severity of this disease complex in recent years. Further research is necessary to understand these changes.

Original languageEnglish (US)
Pages (from-to)1140-1145
Number of pages6
JournalJournal of Veterinary Diagnostic Investigation
Issue number6
StatePublished - Nov 2011
Externally publishedYes


  • Antimicrobial
  • Brachyspira
  • minimum inhibitory concentration
  • swine

ASJC Scopus subject areas

  • veterinary(all)


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