A genus of Gram-positive bacteria. The most notable species of the bacterial genus Erysipelothrix is E. rhusiopathiae. It is pathogenic and causes disease in a variety of animal species, including humans. Erysipelothrix rhusiopathiae is a rod-shaped organism, 0.3 × 1–2 micrometers, that may form filaments in old cultures and in chronically infected tissues. It occurs in the tonsil of healthy swine and on the surfaces of fish and other aquatic species. In addition, it is shed in the urine, oral secretions, and feces of infected animals. Organisms deposited in the soil may survive for years and may be a source of infection for susceptible domestic and wild animals and birds. See also: Bacteria; Bacteriology; Medical bacteriology; Pathogen
Epidemiology and transmission
Erysipelothrix rhusiopathiae causes disease in swine (erysipelas), turkeys, lambs, and a variety of other domestic and wild mammals and birds. Infections are acquired via skin abrasions, or they occur endogenously when organisms residing in the tonsil invade the bloodstream of swine stressed by excessive heat. The organism spreads via contaminated excretions and saliva. Infections in humans are associated with occupational exposure to the organism (veterinarians, butchers, pathologists, and fish-handlers). They are usually acquired via minor cuts and abrasions on the hands or arms, leading to a painful local purplish erythema (reddening of the skin) termed erysipeloid. This infection may occasionally lead to invasion of the bloodstream or joints.
Clinical findings and pathology
In swine, the acute disease develops suddenly with high fever, prostration, conjunctivitis, and death within a day or two of septicemia. A less severe form is associated with rhomboid, deep-red skin lesions and is called diamond skin disease. Chronic swine erysipelas takes the form of verrucous (wartlike) growths on the heart valves and a progressive immune-mediated arthritis resembling rheumatoid arthritis in humans. Polyarthritis is a common manifestation in lambs. The disease is often devastating in turkey flocks, causing mass mortality due to septicemia. A thin capsule on E. rhusiopathiae confers resistance to phagocytosis and intracellular killing by host phagocytes. Hyaluronidase and neuraminidase also contribute to virulence. Multiplication of the organism in phagocytes and subsequent killing of phagocytes are critical in determining the outcome of infection. In the terminal stages, thrombi form in the small blood vessels, which may rupture and hemorrhage.
Diagnosis and treatment
Erysipelothrix rhusiopathiae is easily demonstrated microscopically and by culture of blood and tissues of affected animals. Penicillin is the antibiotic of choice for treatment of infected animals or humans. See also: Penicillin
Control and prevention
Protective immunity is stimulated by live attenuated strains or by inactivated virulent E. rhusiopathiae. A protein is involved in stimulation of protective antibodies. Live vaccines stimulate both enhanced killing activity of phagocytes and protective opsonizing antibodies.