Erysipelothrix rhusiopathiae
- Bacterium
Gram-positive
Thick peptidoglycan wall: stains purple.- Exam priority: medium
A bacterium from pigs and fish that causes a purple, burning skin infection on the hands of people who handle fish or raw meat.
Also called: erysipeloid agent, swine erysipelas bacterium
Quick facts
- Type
- Bacterium · Gram-positive rods
- Gram / shape
- Gram-positive · Thin rod that may form long filaments
- Spread
- Occupational · Occasionally cat or dog bites
- Causes
- Erysipeloid · Diffuse cutaneous erysipeloid
- Treatment
- Penicillin is the drug of choice
At a glance
- Gram
- Gram-positive
- Shape
- Thin rod that may form long filaments
- Oxygen
- Facultative anaerobe
- Family
- Erysipelotrichaceae
Morphology
- Non-spore-forming, non-motile Gram-positive rod
- Catalase-negative and alpha-haemolytic on blood agar
- Produces hydrogen sulfide on triple sugar iron agar, unusual for a Gram-positive rod
Transmission
- Scratches or punctures while handling fish, shellfish, raw pork or poultry
- Occupational: fishers, fishmongers, butchers, slaughterhouse workers and veterinarians
- Occasionally cat or dog bites
- Not spread from person to person
Reservoir: Pigs (swine erysipelas), fish slime, shellfish, poultry; it survives in soil and water
Isolation precautions
What the care team adds to standard precautions.
- Standard
Virulence factors
- A capsule that resists phagocytosis
- Neuraminidase and hyaluronidase that help it spread in tissue
- Strong tendency to reach heart valves once in the blood
Diseases it causes
- Erysipeloid: localised cellulitis of the finger or hand Hand infections (paronychia, felon, flexor tenosynovitis) →
- Diffuse cutaneous erysipeloid with spreading lesions (rare)
- Bacteraemia with infective endocarditis, mostly of the aortic valve Infective endocarditis →
- Septic arthritis Septic Arthritis of the Knee →
Clinical picture
- Within a week of the injury: a raised, violet, sharply bordered plaque on the hand that burns or itches
- The edge spreads slowly while the centre clears; little pus and usually no fever
- Endocarditis often affects native valves, needs surgery often and is linked to alcohol use
Diagnosis
- Occupational history: fish, meat or animal contact
- Full-thickness skin biopsy of the lesion edge for culture or PCR (the bacteria lie deep in the skin)
- Blood cultures if systemic illness; echocardiography if bacteraemic
- May be misidentified as lactobacilli or enterococci
Treatment
Penicillin is the drug of choice; cephalosporins, fluoroquinolones and clindamycin are alternatives. It is intrinsically resistant to vancomycin (and to aminoglycosides and sulfonamides), so empirical vancomycin for Gram-positive rod endocarditis fails.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
- Benzylpenicillin (penicillin G)
- Phenoxymethylpenicillin (penicillin V)
- Ceftriaxone
- Ciprofloxacin
- Clindamycin
Prevention
- Gloves and protection of hand wounds when handling fish, shellfish and raw meat
- Vaccination of pigs is a veterinary measure that reduces the reservoir
Test yourself
Think of the answer, then tap the question to see it.
Which occupations are at risk of erysipeloid?
Those handling fish, shellfish, raw pork or poultry: fishers, fishmongers, butchers and slaughterhouse workers.
Why is it dangerous to treat Erysipelothrix endocarditis empirically with vancomycin?
The organism is intrinsically resistant to vancomycin.
Which biochemical clue is unusual for this Gram-positive rod?
It produces hydrogen sulfide on triple sugar iron agar.
Which sample gives the best yield in erysipeloid?
A full-thickness skin biopsy of the advancing edge, because the bacteria lie deep in the skin.
Connections
← Back to the group: Gram-positive rods
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Erysipeloid - Infectious Disease - MSD Manual Professional Edition (MSD Manual Professional Edition, 2025); Did the updated Duke criteria missed Erysipelothrix rhusiopathiae from the list of typical microorganisms causing infective endocarditis? (Le Infezioni in Medicina, 2023).
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Representative model, for educational purposes only.