Abstract
The United States has a low burden of drug resistance among tuberculosis (TB) cases compared with other world regions. TB is increasingly concentrated among foreign-born individuals who have higher rates of drug resistance than U.S.-born individuals. While universal drug susceptibility testing is the standard for detecting active tuberculosis, there are limited guidelines for latent tuberculosis infection (LTBI) treatment based on risk factors for drug resistance. To quantify the variable risk of drug resistance among foreign-born individuals, all TB cases in Washington State between 1994 and 2014 with drug resistance data for isoniazid, rifampin, pyrazinamide, and ethambutol were divided into eight regions of birth. Logistic regression was used to characterize regional differences in resistance patterns. Genotypic cluster and lineage data were compared against drug resistance in a subanalysis. Among 4,298 cases, isoniazid resistance was more common in foreign-born individuals (12.6% versus 4.8%; P < 0.001), with the highest burden among individuals from the Asia-Pacific (14.8%) region. Rifampin resistance was slightly higher among foreign-born individuals (1.9% versus 1.1%; P = 0.063). Multivariate logistic regression demonstrated that older age was associated with a lower risk of resistance to isoniazid and rifampin (odds ratio [OR] = 0.86, P = 0.006 and OR = 0.64, P = 0.003 for each 20-year interval, respectively). These data suggest drug resistance in LTBI will remain a challenge and that rifampin-based regimens for treatment of LTBI in non-human immunodeficiency virus-infected adults may be preferable for individuals born in regions with high levels of isoniazid resistance. However, further research is needed to demonstrate whether LTBI treatment based on region of birth further decreases TB reactivation.