Factors affecting tuberculosis strain success over 10 years in a high TB- and HIV-burdened community

Background: Factors associated with Mycobacterium tuberculosis (Mtb) strain success over time in high burdened communities are unknown. Methods: Mtb isolates collected over 10 years from sputum-positive tuberculosis (TB) patients resident in the study site underwent IS6110-based restriction fragment length polymorphism analysis. Clinical, demographic and social data were extracted from clinic records and interviewer-administered questionnaires. Strains were defined as persistently successful, transiently successful or unsuccessful based on the average number of cases per year and their continued presence over time. Results: Genotyping data were available on 789 TB cases. Of the 311 distinct Mtb strains (≥6 bands) identified, 247 were categorized as unsuccessful strains, 12 transiently successful and 10 persistently successful strains. Strain success was not associated with age, gender, antiretroviral use or social factors. Persistently successful strains were less likely to be drug-resistant compared with transiently successful strains [odds ratio (OR): 0.13; 95% confidence interval (CI): 0.04-0.5]. Persistently successful strains were positively associated with host HIV-infection compared with unsuccessful strains, but this finding was not robust in sensitivity analyses. Conclusions: Pathogen characteristics appear to play a greater role in Mtb strain success compared with social or host factors. This study supports the need for further investigations into the role of pathogen characteristics in strain success.