The treatment of multidrug-resistant tuberculosis significantly increases the risk of acquired resistance to second-line drugs and the likelihood of upgrading the condition to extensively drug-resistant tuberculosis, according to data from a new study.
For the prospective cohort study conducted in nine countries, the researchers enrolled 1,659 patients with confirmed MDR-TB who started treatment with second-line drugs from 2005 to 2008. Among those, 71.4% had at least one subsequent positive culture after the baseline culture and the analysis cohort included 832 individuals who had their first and last cultures tested successfully.
Sixty-six patients (7.9%) had XDR-TB at baseline and another 68 (8.9%) acquired XDR-TB during treatment. At baseline, 128 patients had fluoroquinolone resistance at baseline and another 79 (11.2%) acquired fluoroquinolone resistance during treatment. In addition, 115 patients (13.8%) had resistance to second-line injectable drugs at baseline, and another 56 (7.8%) acquired resistance.
“If the results of [this study] can be generalized, then policies promoting the use of new drugs in otherwise marginally effective treatment regimens, without at least two or three other highly effective drugs, will lead rapidly to widespread acquired resistance to the new drug,” researchers with the global Preserving Effective TB Treatment Study (PETTS) wrote in Clinical Infectious Diseases.
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