Erysipelothrix rhusiopathiae, a pleomorphic, gram-positive bacillus, is the only species of the genus Erysipelothrix. This organism causes both a self-limited soft-tissue infection (erysipeloid) and serious systemic disease. Erysipelothrix rhusiopathiae is widespread in nature and infects many domestic animals. Swine are probably the major reservoir of E. rhusiopathiae. The microorganism is also found in sheep, cattle, horses, chickens, and dogs, as well as in fish and crabs. Infection in humans is usually due to occupational exposure. Butchers, abattoir workers, fishermen, farmers, and veterinarians are at risk for Erysipelothrix infections. The clinical spectrum of human infection includes localized cutaneous infection, diffuse cutaneous disease, and systemic bloodstream infection.

LOCALIZED CUTANEOUS INFECTION

Erysipeloid of Rosenbach, the localized cutaneous form of illness, is the most common type of human infection caused by E. rhusiopathiae (Figure 134.1). Fingers and/or hands (sites of exposure) are almost always involved in this soft-tissue infection.

Mild pain may occur at the site of inoculation, followed by itching, throbbing pain, burning, and tingling. The characteristic skin lesion slowly progresses from a small red dot at the site of inoculation to a fully developed erysipeloid skin lesion, consisting of a well-developed purplish center with an elevated border. Patients often complain of joint stiffness and pain in the involved fingers, but swelling is minimal or absent. Small hemorrhagic, vesicular lesions may be present at the site of inoculation.