Infectious Disease and Microbiology – Klebsiella granulomatis

Overview

Klebsiella granulomatis, formerly known as Calymmatobacterium granulomatis, is a pleomorphic Gram-negative coccobacillus that causes granuloma inguinale (donovanosis).

Donovanosis is a chronic, progressively destructive infection involving primarily the genital and perianal regions. It occurs predominantly in tropical and subtropical areas and is uncommon in industrialized countries.

Taxonomy

Current name: Klebsiella granulomatis

Former name: Calymmatobacterium granulomatis

Older microbiology and infectious-disease literature frequently uses the former designation.

Microbiologic Characteristics

K. granulomatis is:

• A Gram-negative coccobacillus

• Pleomorphic

• Historically described as aerobic

• An intracellular organism in infected tissue

The classic microscopic finding is the:

Donovan body

Incubation Period

The incubation period is not precisely established but is generally estimated to range from approximately:

1–12 weeks

Because lesions can develop gradually, the precise exposure responsible for infection may be difficult to identify.

Epidemiology

Donovanosis is:

• Uncommon in industrialized countries

• Endemic in some tropical and subtropical regions

• Associated primarily with sexual exposure

The source also notes that occasional clusters have historically occurred in the United States.

Transmission

K. granulomatis is primarily associated with:

Sexual transmission

Risk is related to direct contact with infected lesions.

Granuloma Inguinale

Donovanosis

Infection with K. granulomatis causes:

Granuloma inguinale

also called:

Donovanosis

It is characterized by a chronic, progressive ulcerative disease involving the genital, inguinal, and perianal regions.

Characteristic Lesions

The disease classically produces:

Slowly progressive, painless genital ulcers

The lesions are typically:

• Beefy red

• Granulomatous

• Friable

• Highly vascular

• Prone to bleeding when touched

The combination of a painless, beefy-red ulcer that bleeds easily is particularly characteristic.

Progression

Without appropriate treatment, lesions may:

• Gradually enlarge

• Extend into surrounding tissue

• Become increasingly destructive

• Produce secondary bacterial infection

• Heal with fibrosis or scarring

The disease is generally chronic rather than an acute systemic infection.

Lymphadenopathy

True regional lymphadenopathy is generally uncommon.

However, subcutaneous inflammatory lesions may develop and resemble enlarged lymph nodes. These are sometimes called:

Pseudobuboes

This can help distinguish donovanosis from chancroid and lymphogranuloma venereum.

Diagnosis

The source lists:

Histologic examination

as an important diagnostic method.

Because routine culture is difficult, diagnosis is usually based on demonstration of the organism within affected tissue.

Donovan Bodies

The classic diagnostic finding is:

Donovan bodies

These are intracellular organisms seen within macrophages obtained from affected lesions.

They can be demonstrated using:

• Wright stain

• Giemsa stain

Microscopic Appearance

On microscopy:

Large mononuclear cells/macrophages

contain

Intracytoplasmic rod-shaped organisms

→ Donovan bodies

This is the classic examination clue for K. granulomatis.

Culture

The source notes that:

Culture is difficult and unreliable.

Therefore, routine bacterial culture is generally not the preferred method for establishing the diagnosis.

Treatment

The source recommends:

Doxycycline 100 mg orally every 12 hours

for:

At least 3 weeks

Treatment should continue until:

All lesions have completely healed.

Additional Treatment Options

The source lists alternatives including:

• Azithromycin

• Ciprofloxacin

• Erythromycin

• Trimethoprim-sulfamethoxazole

Regardless of the regimen selected, therapy should generally continue until complete clinical resolution of the lesions.

Treatment Duration

A key feature of donovanosis treatment is that therapy is not based solely on a fixed short course.

Instead:

Treat for at least 3 weeks

AND

Continue until all lesions have completely healed

This prolonged treatment requirement is an important examination point.

Prevention

The major preventive strategy is:

Safer-sex practices

This includes reducing exposure to active genital lesions and appropriate evaluation of sexual partners according to clinical circumstances.

Differential Diagnosis of Genital Ulcers

Donovanosis – Klebsiella granulomatis

→ Painless ulcer

→ Beefy-red and friable

→ Bleeds easily

→ Donovan bodies

Primary syphilis – Treponema pallidum

→ Usually painless, indurated chancre

→ Regional lymphadenopathy may occur

Chancroid – Haemophilus ducreyi

→ Painful, soft genital ulcer

→ Tender suppurative lymphadenopathy/buboes

Genital herpes – HSV

→ Painful grouped vesicles/ulcers

→ Often recurrent

Lymphogranuloma venereum – Chlamydia trachomatis L1–L3

→ Small initial lesion may be transient

→ Later prominent painful regional lymphadenopathy

High-Yield Clinical Pattern

Sexually active patient

• ●

Chronic painless genital ulcer

• ●

Beefy-red, friable lesion that bleeds easily

• ●

Intracellular Donovan bodies on Wright/Giemsa stain

→ Think Klebsiella granulomatis

→ Diagnosis: Donovanosis

Exam Essentials

Organism: Klebsiella granulomatis

Former name: Calymmatobacterium granulomatis

Morphology: Pleomorphic Gram-negative coccobacillus

Incubation: Approximately 1–12 weeks

Distribution: Predominantly tropical/subtropical regions

Transmission: Primarily sexual

Disease: Granuloma inguinale (donovanosis)

Classic lesion: Painless, beefy-red, friable genital ulcer

Bleeding: Lesions characteristically bleed easily

Lymphadenopathy: Usually uncommon; pseudobuboes may occur

Classic diagnostic finding: Donovan bodies

Stains: Wright or Giemsa

Culture: Difficult and unreliable

Treatment in source: Doxycycline 100 mg PO q12h

Duration: At least 3 weeks and until complete healing

Alternatives: Azithromycin, ciprofloxacin, erythromycin, or TMP-SMX

Prevention: Safer-sex practices

Key clinical pearl: Think Klebsiella granulomatis when a patient has a chronic, painless, beefy-red genital ulcer that is friable and bleeds easily. Demonstration of intracellular Donovan bodies on Wright or Giemsa staining is the classic diagnostic clue for donovanosis.