Association between Mycobacterium tuberculosis lineage and time to sputum culture conversion

Abstract

Mycobacterium tuberculosis comprises four principal genetic lineages: one evolutionarily ancestral (Indo-Oceanic) and three modern. Whether response to tuberculosis (TB) treatment differs among the lineages is unknown. To examine the association between M. tuberculosis lineage and time to sputum culture conversion in response to standard first-line drug therapy. We conducted an exploratory retrospective cohort analysis of time to sputum culture conversion among pulmonary tuberculosis (PTB) cases reported in the United States from 2004 to 2007. The analysis included 13,170 PTB cases with no documented resistance to first-line drugs who received a standard four-drug treatment regimen. Among cases with baseline positive sputum smear results, relative to cases with Euro-American lineage, cases with Indo-Oceanic lineage had higher adjusted hazards of sputum culture conversion (aHR 1.32, 95%CI 1.20-1.45), whereas cases with East-African-Indian or East-Asian lineage did not differ (aHR 1.05, 95%CI 0.88-1.25 and aHR 0.99, 95%CI 0.91-1.07, respectively). Among cases with baseline negative sputum smear results, time to sputum culture conversion did not differ by lineage. Although these results are exploratory, they suggest that the eradication of viable bacteria may occur sooner among cases with Indo-Oceanic lineage than among those with one of the three modern lineages. Prospective studies of time to sputum culture conversion by lineage are required.