Comparison of isoniazid monoresistant tuberculosis with drug-susceptible tuberculosis and multidrug-resistant tuberculosis

Limited data exist about the clinical characteristics of Mycobacterium tuberculosis (TB) isolates with resistance to isoniazid (IZN). We describe the demographic and clinical characteristics and risk factor information for persons with IZN monoresistant (resistant to isoniazid) TB compared with drug-susceptible TB and multidrug-resistant (MDR) TB. From 2002 to 2009, 590 cases of TB were diagnosed. Of these, 44 (7.5%) developed MDR-TB and 38 (6.4%) had IZN monoresistant TB. Among the IZN monoresistant TB patients, more common demographic characteristics were former resident of the Soviet Union immigrant, smoker, and previous history of TB (p = 0.005, 0.025, and 0.005, respectively), while HIV, weight loss, and hemoptysis were less common (p = 0.005 for all parameters). The mean length of treatment was 24 ± 4 months for MDR-TB, 10 ± 3 months for IZN monoresistant TB cases, and 8 ± 2 months for all other TB cases. The directly observed therapy (DOT) rate was similar in all three groups. However, treatment failure, completion of TB treatment, and mortality were all similar in drug-susceptible TB and higher in MDR-TB. In multivariate analysis, only a history of previous TB (odds ratio [OR] 1.4; 95% confidence interval [CI]: 1.2–1.6) was significantly associated with IZN monoresistant TB. IZN monoresistant TB has distinct characteristics. However, the length of treatment and outcome are similar to drug-susceptible TB cases.