Mycobacterium africanum (Lineage 6) shows slower sputum smear conversion on tuberculosis treatment than Mycobacterium tuberculosis (Lineage 4) in Bamako, Mali

Bassirou Diarra, Mahamadou Kone, Antieme Combo Georges Togo, Yeya Dit Sadio Sarro, Aissata Boubakar Cisse, Amadou Somboro, Boureima Degoga, Mohamed Tolofoudie, Bourahima Kone, Moumine Sanogo, Bocar Baya, Ousmane Kodio, Mamoudou Maiga, Michael Belson, Susan Orsega, Meryam Krit, Sounkalo Dao, Ibrahim Izétiegouma Maiga, Robert L Murphy, Leen RigoutsSeydou Doumbia, Souleymane Diallo, Bouke Catherine de Jong

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OBJECTIVE: Ancestral M. tuberculosis complex lineages such as M. africanum are underrepresented among retreatment patients and those with drug resistance. To test the hypothesis that they respond faster to TB treatment, we determined the rate of smear conversion of new pulmonary tuberculosis patients in Bamako, Mali by the main MTBc lineages.

METHODS: Between 2015 and 2017, we conducted a prospective cohort study of new smear positive pulmonary tuberculosis patients in Bamako. Confirmed MTBc isolates underwent genotyping by spoligotyping for lineage classification. Patients were followed at 1 month (M), 2M and 5M to measure smear conversion in auramine (AR) and Fluorescein DiAcetate (FDA) vital stain microscopy.

RESULT: All the first six human MTBc lineages were represented in the population, plus M. bovis in 0.8% of the patients. The most widely represented lineage was the modern Euro-American lineage (L) 4, 57%, predominantly the T family, followed by L6 (M. africanum type 2) in 22.9%. Ancestral lineages 1, 5, 6 and M. bovis combined amounted to 28.8%. Excluding 25 patients with rifampicin resistance, smear conversion, both by AR and FDA, occurred later in L6 compared to L4 (HR 0.80 (95% CI 0.66-0.97) for AR, and HR 0.81 (95%CI 0.68-0.97) for FDA). In addition we found that HIV negative status, higher BMI at day 0, and patients with smear grade at baseline ≤ 1+ were associated with earlier smear conversion.

CONCLUSION: The six major human lineages of the MTBc all circulate in Bamako. Counter to our hypothesis, we found that patients diseased with modern M. tuberculosis complex L4 respond faster to TB treatment than those with M. africanum L6.

Original languageEnglish
Article numbere0208603
JournalPLoS ONE
Issue number12
Number of pages12
Publication statusPublished - 2018


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