Members of the genus Erysipelothrix are facultative anaerobic, gram-positive small rods that are ubiquitous in nature, found worldwide, and have been recognized as a cause of infection in animals and humans since the 1880's (Wood and Henderson, 2006). Strains have been isolated from many wild and domestic animal species including reptile, fish, amphibians, and humans; however, Erysipelothrix spp. is most economically important as the cause of swine erysipelas (Wood, 1984). As one of the oldest diseases recognized by the swine industry, the isolation and diagnosis of swine erysipelas continues to hinder laboratory technicians and diagnosticians worldwide. This is evidenced by numerous protocols that have been described in the literature examining different culture and molecular methods aimed to isolate and identify Erysipelothrix. Diagnosis is complicated due to cultural characteristics, notably small colony size, and small numbers of organisms present in lesions (Fidalgo et al., 2000). Isolation of the organism from contaminated specimens further compounds the issue and potential errors related to recognition have been reported (Dunbar and Clarridge, III, 2000). Chapter 3 describes the development and validation of a modified enrichment broth technique for the isolation of Erysipelothrix from experimentally and naturally infected swine (Bender et al., 2009). This research indicates that an enrichment broth technique should be used by veterinary diagnostic laboratories.

Data from the United States Department of Agriculture (USDA) continues to implicate swine erysipelas as one of the top ten reasons for swine condemnations at slaughter. Economic losses due to Erysipelothrix infection occur from increased numbers of acute deaths, treatments costs, vaccination costs, and slow growth of diseased pigs (Wood, 1984). Chapter 4 describes the adoption of an enrichment broth technique to investigate condemnations at slaughter suspected to be due to swine erysipelas. In addition, isolates obtained from condemned tissues were further characterized to evaluate the potential presence of new Erysipelothrix strains as this has not been investigated since the 1970's.

Chapter 5 describes research which aimed to identify and further characterize Erysipelothrix isolates from swine tissues and environments from six Midwestern United States swine sites. Research in this area has not been conducted on swine sites in the United States regarding swine erysipelas and associated tissue and environmental interaction also since the 1970's (Wood, 1973; Wood, 1974; Wood and Packer, 1972). Furthermore, Erysipelothrix spp. isolates currently used in vaccine strains utilized on the sites were compared to the recovered isolate and recently described molecular assays were utilized to further characterize all isolates (Ingebritson et al., 2010; Shen et al., 2010; To and Nagai, 2007).