Clinical Relevance of Non-Tuberculous Mycobacteria in Zambia

Tuberculosis, especially due to the high prevalence of HIV, remains a problem of large dimension in Africa and Mycobacterium tuberculosis is the most important causative agent. However, it is known that in developed countries also nontuberculous mycobacteria (NTM) play a significant role in the aetiology of tuberculosis-like syndromes, especially in HIV-positive patients. In Africa, the contribution of NTM to the problem of tuberculosis has hardly been examined. Southern Africa is the most affected sub-region in Africa concerning HIV/AIDS, where HIV prevalence rates have stabilized at high levels, exceeding 25% in some countries, while in other African countries, the epidemic is still growing. In Zambia the estimated adult (15-49 yrs) prevalence of HIV/AIDS amounted 13.5-20% in 2003 (61). NTM disease was one of the major AIDS-defining diseases in industrialized countries before the era of highly active antiretroviral therapy (HAART). Such infections have been thought to be less frequent in sub-Saharan Africa, but with the remaining doubt that the unavailability of the laboratory facilities and sophisticated radiological tools required to diagnose such disease may lead to underestimating of their true frequency (9,12,24,27,37,41,47). Whereas an international prospective study showed that NTM prevalence for disease was five to 10-fold lower in Kenya than in the United States of America or Northern Europe (24), a few hospital-based studies have reported a different prevalence for disease than reported in Kenya (9,12,27,37,41,47). For an overview of the literature on prevalence/incidence rates of colonization/infection/disease of NTM in Africa see Table 1 in the introduction of this thesis. Because the clinical relevance of the isolation of NTM in HIV-positive as well as in HIV-negative patients in Africa may be underestimated in this study, the meaning of NTM was examined in more detail in Zambia.

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