Extensive drug resistance acquired during treatment of multidrug-resistant tuberculosis.

Clinical Infectious Diseases

PubMedID: 25057101

Cegielski JP, Dalton T, Yagui M, Wattanaamornkiet W, Volchenkov GV, Via LE, Van Der Walt M, Tupasi T, Smith SE, Odendaal R, Leimane V, Kvasnovsky C, Kuznetsova T, Kurbatova E, Kummik T, Kuksa L, Kliiman K, Kiryanova EV, Kim H, Kim CK, Kazennyy BY, Jou R, Huang WL, Ershova J, Erokhin VV, Diem L, Contreras C, Cho SN, Chernousova LN, Chen MP, Caoili JC, Bayona J, Akksilp S, Global Preserving Effective TB Treatment Study (PETTS) Investigators. Extensive drug resistance acquired during treatment of multidrug-resistant tuberculosis. Clin Infect Dis. 2014;59(8):1049-63.
BACKGROUND
Increasing access to drugs for the treatment of multidrug-resistant (MDR) tuberculosis is crucial but could lead to increasing resistance to these same drugs. In 2000, the international Green Light Committee (GLC) initiative began to increase access while attempting to prevent acquired resistance.

METHODS
To assess the GLC's impact, we followed adults with pulmonary MDR tuberculosis from the start to the end of treatment with monthly sputum cultures, drug susceptibility testing, and genotyping. We compared the frequency and predictors of acquired resistance to second-line drugs (SLDs) in 9 countries that volunteered to participate, 5 countries that met GLC criteria, and 4 countries that did not apply to the GLC.

RESULTS
In total, 832 subjects were enrolled. Of those without baseline resistance to specific SLDs, 68 (8.9%) acquired extensively drug-resistant (XDR) tuberculosis, 79 (11.2%) acquired fluoroquinolone (FQ) resistance, and 56 (7.8%) acquired resistance to second-line injectable drugs (SLIs). The relative risk (95% confidence interval [CI]) of acquired resistance was lower at GLC-approved sites: 0.27 (.16-.47) for XDR tuberculosis, 0.28 (.17-.45) for FQ, and 0.15 (.06-.39) to 0.60 (.34-1.05) for 3 different SLIs. The risk increased as the number of potentially effective drugs decreased. Controlling for baseline drug resistance and differences between sites, the odds ratios (95% CIs) were 0.21 (.07-.62) for acquired XDR tuberculosis and 0.23 (.09-.59) for acquired FQ resistance.

CONCLUSIONS
Treatment of MDR tuberculosis involves substantial risk of acquired resistance to SLDs, increasing as baseline drug resistance increases. The risk was significantly lower in programs documented by the GLC to meet specific standards.