Epidemiology of drug-resistant tuberculosis in Texas

During 1987-1996, over 22,000 tuberculosis cases were reported in Texas, at an average annual incidence rate of 12.5 cases per 100,000 population. Counties with the highest rates were located along the Mexico-Texas border and in northwestern Texas. Nine percent of cases were resistant to at least one of the five first-line antituberculosis drugs used for treatment. Almost 5 percent (4.6%) were resistant to isoniazid, either alone or in combination with other antibiotics; 2.3% were resistant to rifampin; and only 1.3% were resistant to both isoniazid and rifampin. Being a recurrent case, being foreign-born, being 20-39 years of age, and residing in a Mexico-Texas border county were independent risk factors for isoniazid resistance and rifampin resistance. Tuberculosis patients with human immunodeficiency virus (HIV) infection were more likely to have rifampin resistance and less likely to have isoniazid resistance than patients without HIV infection. Factors associated with multi-drug-resistant tuberculosis included a history of previous tuberculosis (relative risk (RR) = 4.91, 95% confidence interval (CI) 3.5-6.8), non-US birth (RR = 2.69, 95% CI 2.1-3.5), age younger than 20 years (RR = 1.97, 95% CI 1.1-3.5), age 20-39 years (RR = 1.82, 95% CI 1.3-2.6), and residence in a Mexico-Texas border county (RR = 2.33, 95% CI 1.8-3.1).