Erysipelothrix rhusiopathiae is a significant bacterial pathogen of swine, turkeys and sheep. It is distributed worldwide and has also been isolated from cattle, horses, dogs, cats, domestic poultry, and wild animals and birds. Erysipeloid, a condition characterized by localized skin infections and cellulitis, may develop in people who work with infected animals, infected carcasses, or infected animal byproducts.

The bacterium can survive in the soil for up to 5 wk; however, soil is not an effective growth medium, and the organism is unable to survive for extended periods of time in the environment. Soil and surface water contamination represent routes of exposure. Asymptomatic carriers are the usual source of infectious organisms but the bacteria may also be introduced to animal production units by surface water runoff, wild mammals, wild birds, pets, and biting insects. E rhusiopathiae has food safety implications, because it can survive for several months in animal tissues such as frozen or chilled pork, cured and smoked ham, and feed byproducts such as dried blood.

E rhusiopathiae is a nonmotile, gram-positive, facultative anaerobic bacillus. It is catalase negative, coagulase positive, oxidase negative, resistant to high salt concentrations, and produces H₂S on triple sugar iron media. The bacterium exhibits colonial pleomorphism, depending on whether an infection is acute or chronic. In acute infections, isolates form smooth colonies on culture media, while rough colonies are typical of isolates recovered from chronically infected animals. Smears prepared from smooth colonies appear as slender, gram-positive rods, and smears prepared from rough colonies appear as a mixture of rods and filaments.

The organism is very hardy and can survive and grow in a wide range of pH and environmental temperatures. E rhusiopathiae has demonstrated the ability to resist the action of several classes of disinfectants used in animal production units including alcohols, aldehydes, oxidizing agents, and phenols. Classes of disinfectants and/or compounds considered to be effective at killing E rhusiopathiae include hypochlorites (bleach) and caustic soda (lye; NaOH). The organism is sensitive to the beta-lactam (penicillin, ampicillin), cephalosporin (ceftiofur), and tetracycline classes of antibiotics and is resistant to sulfonamides.

Last full review/revision March 2012 by Darryl Ragland, DVM, PhD