#10-050

Complete

Date Full Report Received

03/06/2012

Date Abstract Report Received

03/06/2012

Investigation

Institution:
Primary Investigator:

Brachyspira infection(s) appear to growing in importance in today’s swine industry. While largely disappearing from U.S. swine herds between the late 1990’s and the early 2000’s, Brachyspira-associated disease and Brachyspira spp. isolation from swine with clinical disease has increased in the last several years with non-B. hyodysenteriae isolates being more commonly identified.  Antimicrobial resistance may have a role in this resurgence.  Seventy-nine clinical isolates identified at the Iowa State University Veterinary Diagnostic Lab (ISU VDL) were tested with multiple PCR assays that were evaluated and/or developed as part of this study to establish species identity. Isolates were then tested for antibiotic sensitivity to lincomycin, gentamicin, valnemulin, tiamulin, salinomycin, and carbadox.  Only 38.0 % of isolates could be confirmed as the known pathogens B. hyodysenteriae (30.4%) or B. pilosicoli (7.6%).  Twenty of the 79 isolates (25.3%) were identified as B. murdochii and 13.9% could not initially be identified to species. Subsequently, a new PCR assay was developed targeting a potentially novel species of Brachyspira identified by Dr. John Harding’s group as ‘Brachyspira spp. SASK30446’. This new PCR test positively identified these remaining isolates. The antibiotic testing indicated resistance to lincomycin for all Brachyspira; and moderately high resistance against gentamicin.  The Brachyspira tested appeared to be more susceptible to the remaining antimicrobials.  B. murdochii and Brachyspira spp. SASK30446 appeared to be more resistant to several of these drugs than the other Brachyspira examined.  The increased incidence of these less definitively characterized Brachyspira species with increased resistance 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 better understand these changes. For any questions regarding these finding, please contact the Iowa State University Veterinary Diagnostic Laboratory.