Improved diagnostics and further investigation of condemnations and outbreaks associated with Erysipelothrix spp

The objective of this study was to compare the diagnostic performance of a direct isolation method for Erysipelothrix spp. with a broth-based enrichment technique. Samples were obtained from three sources: (1) experimentally inoculated pigs, (2) porcine tissue samples submitted to the Iowa State University Veterinary Diagnostic Laboratory, and (3) tissues from condemned carcasses at an abattoir. Culture plates from direct isolation and broth-based technique were evaluated for growth at 24 and 48 hrs. Results indicated that the broth enrichment method was markedly more sensitive for the isolation of Erysipelothrix spp. To the authors’ knowledge, this is the first comparison of direct culture and broth-based enrichment methods for the isolation of Erysipelothrix spp. Interestingly, in several samples a Gram-positive bacterium with almost identical growth characteristics to Erysipelothrix spp. was detected and identified as a Vagococcus spp. through 16S rRNA gene sequencing. The results of this study indicate that the broth-based enrichment method should be used for