Infectious Disease and Microbiology – Erysipelothrix rhusiopathiae

Overview

Erysipelothrix rhusiopathiae is a Gram-positive bacillus that causes a characteristic occupational skin infection known as erysipeloid. Human infection is uncommon but occurs worldwide and is strongly associated with exposure to fish, shellfish, animals, animal products, or contaminated soil.

Although most infections remain localized to the skin, the organism can occasionally cause diffuse cutaneous disease, bacteremia, and infective endocarditis.

Microbiologic Characteristics

Erysipelothrix rhusiopathiae is an:

• Aerobic Gram-positive bacillus

• Zoonotic pathogen

• Environmental and animal-associated organism

It is especially notable for causing infection after inoculation through minor skin trauma during occupational exposure.

Incubation Period

The incubation period is:

Not clearly defined

Clinical infection usually follows direct inoculation of the organism into damaged skin.

Epidemiology

Human infection is rare but occurs worldwide.

Exposure is classically associated with people who handle:

• Fish

• Crustaceans and shellfish

• Meat or animal carcasses

• Livestock

• Animal products

• Soil contaminated by animals

Occupational risk is therefore increased in fish handlers, butchers, veterinarians, farmers, and similar workers.

Erysipeloid

The classic localized infection caused by E. rhusiopathiae is called:

Erysipeloid

This is a localized cutaneous infection that usually develops at the site of inoculation.

Clinical Features of Erysipeloid

Typical findings include:

• Painful or burning skin lesion

• Erythematous to violaceous discoloration

• Well-demarcated margins

• Gradual peripheral expansion

• Common involvement of the hands or fingers

Systemic symptoms are usually absent or mild in localized disease.

Diffuse Cutaneous Disease

Some patients may develop a more widespread cutaneous eruption accompanied by systemic symptoms.

Possible manifestations include:

• Fever

• Myalgias

• Arthralgias

• Multiple skin lesions

This represents a more extensive form of infection than classic localized erysipeloid.

Bacteremia

Rarely, E. rhusiopathiae can invade the bloodstream and cause:

Bacteremia

Bloodstream infection should raise concern for deeper or systemic involvement.

Infective Endocarditis

One of the most important severe manifestations is:

Infective endocarditis

Historically, E. rhusiopathiae bacteremia has had a notable association with endocarditis.

Patients with systemic infection may therefore require evaluation for cardiac involvement when clinically appropriate.

Diagnosis

Diagnosis is established by:

Culture of the organism

Specimens depend on the clinical syndrome and may include tissue or blood.

Because localized lesions can have relatively few organisms, obtaining an appropriate deeper specimen may improve diagnostic yield.

Treatment

The source recommends:

Penicillin G for 10 days

Penicillin has traditionally been considered an effective treatment for susceptible E. rhusiopathiae infection.

Additional Treatment Options

Alternative agents listed in the source include:

• Cephalosporins

• Clindamycin

• Ciprofloxacin

• Carbapenems such as imipenem or meropenem

Choice of therapy should depend on disease severity and susceptibility when available.

Important Antibiotic Pearl

A useful microbiology distinction is that Erysipelothrix rhusiopathiae is characteristically resistant to vancomycin.

This is clinically important because vancomycin is often used empirically for Gram-positive infections, but it is not a reliable treatment for this organism.

Occupational Exposure Pattern

A classic exposure history is:

Fish or animal handler

• ●

Minor cut or puncture wound

• ●

Painful violaceous hand lesion

→ Think Erysipelothrix rhusiopathiae

Differential Diagnosis

Localized erysipeloid may resemble:

• Cellulitis

• Erysipelas

• Contact dermatitis

• Other occupational skin infections

The exposure history is often the major clue.

High-Yield Clinical Pattern

Handling fish, shellfish, meat, or animals

• ●

Localized painful violaceous skin lesion on the hand

• ●

Gram-positive bacillus

→ Think Erysipelothrix rhusiopathiae

Severe Disease Pattern

Systemic symptoms or bacteremia

• ●

Possible cardiac murmur or persistent bloodstream infection

→ Evaluate for infective endocarditis

Exam Essentials

Organism: Erysipelothrix rhusiopathiae

Type: Gram-positive bacillus

Distribution: Worldwide

Frequency: Rare

Classic disease: Erysipeloid

Typical exposure: Fish, crustaceans, animals, meat, or soil

Common site: Hands and fingers after occupational inoculation

Systemic manifestations: Fever, myalgias, arthralgias

Serious complications: Bacteremia and endocarditis

Diagnosis: Culture

Traditional treatment: Penicillin G

Alternative agents: Cephalosporins, clindamycin, ciprofloxacin, carbapenems

Important resistance clue: Vancomycin resistance

Key clinical pearl: Erysipelothrix rhusiopathiae should be suspected in a fish or animal handler with a painful violaceous hand lesion, and severe bacteremic disease is particularly important because of its association with infective endocarditis.