Infectious Disease and Microbiology – Corynebacterium minutissimum

Overview

Corynebacterium minutissimum is an aerobic Gram-positive bacillus best known as a common cause of erythrasma, a superficial skin infection that typically affects intertriginous areas. Although usually limited to the skin, the organism can rarely cause invasive disease such as bacteremia, sepsis, or endocarditis, particularly in immunocompromised patients.

Microbiologic Characteristics

C. minutissimum is an aerobic, Gram-positive bacillus belonging to the genus Corynebacterium.

It is primarily associated with superficial cutaneous infection, but under certain conditions it can invade deeper tissues or enter the bloodstream.

Epidemiology

C. minutissimum is a relatively common cause of superficial skin infection.

Erythrasma is especially associated with warm, moist areas of the body and is often seen in skin folds.

Erythrasma

The most characteristic infection caused by C. minutissimum is erythrasma.

It typically presents as:

• Well-demarcated reddish-brown patches

• Mild scaling

• Minimal inflammation

• Involvement of intertriginous areas such as the groin, axillae, or toe webs

The lesions may be asymptomatic or mildly pruritic.

Wood’s Lamp Examination

A classic diagnostic finding in erythrasma is coral-red fluorescence under a Wood’s lamp.

This occurs because C. minutissimum produces porphyrin compounds that fluoresce under ultraviolet light.

This finding is highly useful in distinguishing erythrasma from other intertriginous dermatoses.

Systemic Infection

Although uncommon, C. minutissimum can cause more serious invasive infections.

Reported manifestations include:

• Sepsis

• Endocarditis

• Bacteremia

• Subcutaneous tissue infection

These complications are more likely in patients with significant immunosuppression, particularly those with neutropenia.

Subcutaneous Tissue Infection

The organism may occasionally invade deeper tissues and produce localized subcutaneous infection.

Such cases should be evaluated carefully because they may indicate impaired host defenses or deeper tissue involvement.

Diagnosis

Diagnosis is based on:

• Culture of the organism from an appropriate clinical specimen

• Wood’s lamp examination in suspected erythrasma

The combination of a typical intertriginous rash and coral-red fluorescence strongly supports the diagnosis of erythrasma.

Treatment of Erythrasma

A classic systemic treatment regimen is:

Erythromycin 250 mg orally every 6 hours for 14 days

Local treatment with:

2% aqueous clindamycin

may also be effective.

Additional Treatment

Another option is:

Tetracycline 250 mg orally every 6 hours

Treatment choice may depend on severity, extent of disease, tolerance, and antimicrobial susceptibility where relevant.

Treatment of Systemic Infection

For serious systemic infection caused by C. minutissimum, such as sepsis or endocarditis:

Vancomycin is an important treatment option.

Management should also include evaluation for the source of infection and any underlying immunosuppressive condition.

High-Yield Clinical Pattern

Brown-red rash in a skin fold

• ●

Coral-red fluorescence with Wood’s lamp

→ Think Corynebacterium minutissimum causing erythrasma

Exam Essentials

Organism: Corynebacterium minutissimum

Type: Aerobic Gram-positive bacillus

Classic disease: Erythrasma

Typical site: Intertriginous skin folds

Key diagnostic clue: Coral-red fluorescence under Wood’s lamp

Other infections: Subcutaneous infection, sepsis, endocarditis

High-risk group for invasive disease: Neutropenic patients

Diagnosis: Culture and Wood’s lamp examination

Treatment of erythrasma: Erythromycin or topical clindamycin

Treatment of systemic infection: Vancomycin

Key clinical pearl: The classic association is erythrasma + coral-red Wood’s lamp fluorescence = Corynebacterium minutissimum.