(HealthDay News) – Nearly half of patients with tuberculosis in eight countries show resistance to at least one second-line drug, with previous treatment with second-line drugs strongly associated with resistance to these drugs and with extensively drug-resistant (XDR) tuberculosis.
Tracy Dalton, PhD, from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues examined resistance to second-line antituberculosis drugs among 1,278 patients from Estonia, Latvia, Peru, Philippines, Russia, South Africa, South Korea, and Thailand. To identify risk factors for resistance to second-line drugs and XDR tuberculosis, the results were compared with clinical and epidemiological data.
The researchers found that 43.7% of patients showed resistance to at least one second-line drug, with 20.0% showing resistance to at least one second-line injectable drug and 12.9% to at least one fluoroquinolone. A total of 6.7% of patients had XDR, which ranged from 0.8–15.2% across study sites. The strongest risk factor for resistance to second-line drugs was previous treatment with second-line drugs, which was linked with more than a four-fold increase in the risk of XDR tuberculosis. Women more frequently experienced fluoroquinolone resistance and XDR tuberculosis, compared with men. Resistance to second-line injectables was correlated with unemployment, alcohol abuse, and smoking.
“Previous treatment with second-line drugs is a strong, consistent risk factor for resistance to these drugs, including XDR tuberculosis,” the authors write. “Representative drug-susceptibility results could guide in-country policies for laboratory capacity and diagnostic strategies.”