Mycobacterial diseases

The main diseases caused by mycobacterial infection are tuberculosis (TB) and leprosy. Despite a fall in the prevalence of these diseases over the last decade, they are still significant causes of morbidity and mortality worldwide. Atypical mycobacterial infections are encountered less frequently. Immigration patterns, the frequency of human immunodeficiency infection, and the increased numbers of patients on immunosuppressive treatments render mycobacterial infections relevant not only to physicians in the developing world where they traditionally occurred but also in the developed world. Skeletal TB occurs in 1–3% of cases of TB infection, and is more frequently encountered in the immunocompromised. A high index of suspicion is required, diagnosis relies on a combination of clinical features and radiological, histological, and microbiological tests. Multidrug regimens are required for treatment with surgery in selected cases. Leprosy is caused by M. leprae infection. The disease is still a leading cause of disability worldwide. Diagnosis is usually clinical. The course of the disease is indolent but may be interrupted by acute inflammatory reactions, which contribute to nerve damage and disability. Treatment aims at eliminating the mycobacteria using multidrug regimens, and management of complications including leprosy reactions and long-term nerve damage. Atypical mycobacterial infections affecting bone and joints are uncommon; they usually follow direct inoculation of the pathogen. Haematogenous dissemination is encountered in immunocompromised patients. These microorganisms are not usually susceptible to the same drug regimens used in the treatment of tuberculosis.