Table 6.3. True and false fungal infections

Streptomycosis madurae

Synonyms

Actinomadura madurae. Nocardia indica.

Definition

Streptomycosis madurae is an infection with Actinomadura madurae, causing chronic granulomatous suppurative disease, most often localized in one foot and affecting the bones extensively (see previous section).

Geographic Distribution

Actinomadura madurae is very widespread: it is found in India, Africa (especially North Africa), Mexico, and the Mediterranean countries. It is common in South America and has been reported occasionally in other parts of the world.

Epidemiology and Pathology

The mode of entry is through the skin, often of the unshod or poorly protected foot of a farmer or other field worker. The primary lesion is locally invasive and slowly progressive. It forms a hard, localized tumor-like mass which subsequently softens at the center due to necrosis. The necrotic contents are then discharged through a sinus. The infection spreads more deeply, breaching the muscle and fascial planes. As the infection traverses the tissue layers and invades bone, abscesses form aroung the colonies of branching filamentous bacteria, and a granulomatous reaction surrounds the abscess. Sinuses discharge yellow sulfur grains (bacterial colonies) and necrotic tissue. A. madurae grows slowly on artificial media and forms a white or yellow tinted colony.

Clinical Characteristics

The patients are usually in good health: the clinical history starts with tissue damage (from a splinter, bite, or other injury) a few months or even years previously. There is relatively little pain and walking is possible even when the infection is in the foot. The tissues are swollen and covered by multiple nodules, each containing a sinus (see Clinical Characteristics of Madura Foot; Mycetoma; Maduromycosis and Fig. 6.20 A-C for a more detailed description)

Imaging Diagnosis

Imaging shows the soft tissue nodular masses and their extent (Fig. 6.25). When there is a granuloma growing slowly near a bone, there will be a smooth indentation causing progressive notching of the cortex. If this granuloma is situated between closely opposed bones, or joints, such as the metatarsal heads, the bones will be forced apart as the granuloma enlarges. This is a frequent finding. Although the infection may spread widely, remarkably the arch of the foot is usually preserved.

Actinomadura madurae easily invades bone: the periosteum "gives way." Where bone has been invaded, there are spicules of reactive periosteal new bone which can be clearly imaged. Lucent defects develop in the cortex, about 6 mm in diameter and uniform in size in any part of the bone, whether mid-shaft or at the ends (Fig. 6.25 E). There can be large defects in the sesamoid bones. In the later stages the joints become affected (see Table 6.2).

Arteriography shows that the granulomas are hyperemic and contain microarteriovenous fistulae. The contrast causes a "blush" and there is early venous return.