Mycobacterium tuberculosis mixed infections and drug resistance in sub-Saharan Africa: a systematic review

BACKGROUND: Sub-Saharan Africa, is a region that records high rates of TB infection. Mycobacterium tuberculosis mixed strain infection, especially when the strains involved are of different susceptibilities, is an area of great interest because it is linked with an increased risk of treatment failure and transmission of resistant strains within the population. This paper reviewed original studies that reported MTB mixed infection and heteroresistance in the region between 2010 and 2020 to understand the extent of mixed strain infection and heteroresistance in the region. This information is very critical in the control of TB and ending the TB epidemic by 2035 as per the World Health Organization's vision. METHODS: pubmed, Scopus, JSTOR, AJOL, and Google Scholar databases were searched through both key terms and subject headings. The literature was screened, assessed for the quality and evidence synthesized. RESULTS: Eighteen original articles were included in this review after having met the inclusion criteria. The frequency of mixed strain infection reported in these studies varied between 2.8% and 21.1% while drug resistance range between 0.06% to 19% depending on the study design and the drug susceptibility screening technique utilized. The majority of the studies (50%) utilized Spoligotyping in conjunction with MIRU-VNTR typing in the detection of mixed infections. CONCLUSION: Despite the scarcity of data on mixed infections and heteroresistance in sub-Saharan Africa, various studies have revealed that these conditions are frequent in the region than previously thought. Given the evidence of the effect of mixed infections on drug resistance and treatment outcome, we conclude that mixed infection is an unavoidable topic for future studies.