Setting

The impact of the genetic characteristics of Mycobacterium tuberculosis on the clustering of multidrug-resistant tuberculosis (MDR-TB) has not been analyzed together with clinical and demographic characteristics.

Objective

To determine factors associated with genotypic clustering of MDR-TB in a community-based study.

Design

We measured the proportion of clustered cases among MDR-TB patients and determined the impact of clinical and demographic characteristics and that of three M. tuberculosis genetic characteristics: lineage, drug resistance-associated mutations, and rpoA and rpoC compensatory mutations.

Results

Of 174 patients from California and Texas included in the study, the number infected by East-Asian, Euro-American, Indo-Oceanic and East-African-Indian M. tuberculosis lineages were respectively 70 (40.2%), 69 (39.7%), 33 (19.0%) and 2 (1.1%). The most common mutations associated with isoniazid and rifampin resistance were respectively katG S315T and rpoB S531L. Potential compensatory mutations in rpoA and rpoC were found in 35 isolates (20.1%). Hispanic ethnicity (OR 26.50, 95%CI 3.73-386.80), infection with an East-Asian M. tuberculosis lineage (OR 30.00, 95%CI 4.20-462.40) and rpoB mutation S531L (OR 4.03, 95%CI 1.05-23.10) were independent factors associated with genotypic clustering.

Conclusion

Among the bacterial factors studied, East-Asian lineage and rpoB S531L mutation were independently associated with genotypic clustering, suggesting that bacterial factors have an impact on the ability of M. tuberculosis to cause secondary cases.