Mycobacterium ulcerans

Mycobacterium ulcerans

A traveler with a Buruli ulcer on the leg.

Mycobacterium ulcerans is a slow-growing bacterium that is the causative agent of Buruli ulcer, a chronic debilitating skin and soft tissue infection. This organism is part of the Mycobacterium genus, which also includes the pathogens responsible for tuberculosis and leprosy.

Characteristics

Mycobacterium ulcerans is an acid-fast bacillus, meaning it retains certain dyes after being washed with acidic solutions. This characteristic is shared with other mycobacteria. The bacterium grows optimally at temperatures between 29°C and 33°C, which is lower than the body temperature of humans, explaining its predilection for cooler areas of the body such as the skin.

Pathogenesis

The pathogenesis of Mycobacterium ulcerans is primarily due to the production of a toxin called mycolactone. Mycolactone is a polyketide-derived macrolide that causes tissue necrosis and immunosuppression. The toxin's effects lead to the characteristic ulcers seen in Buruli ulcer disease.

Epidemiology

Buruli ulcer is most commonly found in rural areas of West Africa, but cases have been reported in over 30 countries worldwide, including regions in Australia, Southeast Asia, and South America. The exact mode of transmission of Mycobacterium ulcerans is not fully understood, but it is believed to be associated with aquatic environments.

Clinical Presentation

The disease typically begins as a painless nodule or papule, which can progress to a large ulcer with undermined edges. The ulceration is often painless, which can delay diagnosis and treatment. If left untreated, Buruli ulcer can lead to significant morbidity, including scarring and contractures.

Diagnosis

Diagnosis of Mycobacterium ulcerans infection is primarily clinical, supported by laboratory tests such as polymerase chain reaction (PCR) to detect mycobacterial DNA, microscopy of stained smears, and culture of the organism from tissue samples.

Treatment

Treatment of Buruli ulcer involves a combination of antibiotics, typically rifampicin and clarithromycin or streptomycin, for a period of 8 weeks. Surgical intervention may be necessary for extensive lesions to remove necrotic tissue and promote healing.

Related pages

• Buruli ulcer
• Mycobacterium
• Tuberculosis
• Leprosy