Mycobacterium africanum
Encyclopedia
Mycobacterium africanum is a species of Mycobacterium that is most commonly found in West African countries. The symptoms of infection resemble those of M. tuberculosis.
It is a member of the Mycobacterium tuberculosis complex
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It has a similar degree of infectivity to the regular M. tuberculosis organism but is less likely to progress to clinical disease in an immunocompetent individual.
M. africanum is more likely to progress from infection to causing disease in an HIV positive patient, hence in countries where M. africanum is endemic, it represents an important opportunistic infection of the later stages of HIV disease.
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It is a member of the Mycobacterium tuberculosis complex
Mycobacterium tuberculosis complex
Mycobacterium tuberculosis complex refers to a genetically closely related group of Mycobacterium species that can cause tuberculosis.It includes:* Mycobacterium tuberculosis* Mycobacterium africanum* Mycobacterium bovis...
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Epidemiology
M. africanum is most commonly found in West African countries, causing up to a quarter of cases of tuberculosis in countries such as the Gambia. It is an infection of humans only and is spread by an airborne route from individuals with open cases of disease.It has a similar degree of infectivity to the regular M. tuberculosis organism but is less likely to progress to clinical disease in an immunocompetent individual.
M. africanum is more likely to progress from infection to causing disease in an HIV positive patient, hence in countries where M. africanum is endemic, it represents an important opportunistic infection of the later stages of HIV disease.
Pathogenesis
It is not fully understood how the genetic differences between M. africanum and M. tuberculosis give rise to the lower pathogenicity of the former. However, it is known that the Region of Difference 9 (RD9) is lacking in M. africanum but present in M. tuberculosis (Brosch, et al. 2002 PNAS 99:3684).