Clinical Pearls & Morning Reports
Erysipelothrix rhusiopathiae can infect humans after animal exposure. Read the NEJM Case Records of the Massachusetts General Hospital here.
Q: Workers in what occupations are most at risk for E. rhusiopathiae infection?
A:rhusiopathiae is a nonsporulating, gram-positive, rod-shaped bacterium. E. rhusiopathiae has been isolated from multiple animals and is widespread in the environment. The infection is most common in those who handle fresh or frozen fish or crabs; slaughterhouse workers, butchers, and farmers are also at risk. In addition to infecting fish, shellfish, and swine, it can be found in cattle, horses, sheep, turkeys, chickens, cats, dogs, and other animals.
Q: Describe the different presentations of E. rhusiopathiae infection.
A: When the infection occurs in humans, the most common presentation is a localized cutaneous disease known as erysipeloid. In humans, most erysipeloid lesions occur on the fingers after occupational exposure to animals. In some cases, E. rhusiopathiae may cause an infectious syndrome other than erysipeloid, such as a diffuse cutaneous form, bacteremia with possible seeding of distant sites, or endocarditis.
A: Erysipeloid manifests as cellulitis 2 to 7 days after exposure to E. rhusiopathiae. Violaceous and well-defined lesions are typical, and vesicles may develop. Early pain and localized swelling without pitting edema are thought to be characteristic clinical manifestations. Lymphangitis and regional lymphadenopathy may occur. Systemic symptoms are relatively uncommon with localized erysipeloid, but fever may occur.
A: In the clinical microbiology laboratory, it can be visualized on Gram’s staining and recovered in bacterial culture, although a deep-tissue specimen may be needed. Blood cultures are rarely positive in patients with erysipeloid. Bacterial identification can present a challenge to the clinical microbiology laboratory, because at least two different morphotypes in colonies and on Gram’s staining have been reported. However, accurate identification of the pathogen is critical to ensure effective antimicrobial therapy, because erysipelothrix species are intrinsically resistant to vancomycin and many isolates can also be resistant to aminoglycosides and sulfonamides.