Binational Transmission of Multidrug-Resistant Tuberculosis, California & Mexico

Funded by NIDA grant 1K01AI083784-01; PI: Timothy Rodwell

Despite a declining tuberculosis (TB) incidence in California and vigorous public health efforts to prevent Multidrug-resistant tuberculosis (MDR-TB), there are still 40-50 cases per year in California—the highest incidence in the US. In California, over 85% of the incident MDR-TB cases from 1993-2006 were in foreign-born individuals, and 28% were born in Mexico.

We are comparing the genotypes and drug resistance mutation patterns of MDR-TB cases from California and Mexico to determine if the MDR-TB pathogen population is evolving independently on each side of the border, or if cross-border transmission of drug-resistant TB strains is occurring.

The Aims of this study are:

  1. To determine the extent to which the MDR-TB pathogen strains in California are related to those currently circulating in Mexico by comparing MDR-TB genotypes from the Mexican National TB Survey (2008-2009) with the genotypes of MDR-TB isolates from Mexican-born Hispanics in California (2008-2015).
  2. To determine whether INH and RIF drug resistance mutations in binationally distributed MDR-TB strain clusters are predominantly, a) the same (same genotype, same drug mutations), suggesting binational transmission; or b) different (same genotype, different drug mutations), suggesting independent acquisition of drug resistance in Mexico and California.
  3. To examine the MDR-TB risk factors and mobility characteristics associated with MDR-TB strain clusters distributed within and between California and Mexico.