Pattern of first- and second-line drug resistance among pulmonary tuberculosis retreatment cases in Pakistan.

Background: Drug resistance in general, and multidrug-resistant tuberculosis (MDR-TB) in particular, threatens global tuberculosis (TB) control efforts. Population-based estimates of drug resistance are needed to develop strategies for controlling drug-resistant TB in Pakistan.

Objective: To obtain population-based data on Mycobacterium tuberculosis drug resistance in Pakistan.

Methods: To obtain drug resistance data, we conducted a population-based study of TB cases in all provinces of Pakistan. We performed culture and drug susceptibility testing on M. tuberculosis isolates from patients with a prior history of anti-tuberculosis treatment (retreatment cases) from all over the country.

Results: Of 544 isolates from previously treated cases, 289 (53.1%) were susceptible to all first-line drugs, 255 (46.9%) were resistant to at least one anti-tuberculosis drug and 132 (24.3%) were MDR-TB. Among MDR-TB isolates, 47.0% were ofloxacin (OFX) resistant. Extensively drug-resistant TB was found in two (0.4%) isolates.

Conclusion: Prevalence of drug resistance in retreatment isolates was high. The alarmingly high prevalence of OFX resistance among MDR-TB isolates may threaten the success of efforts to control and treat MDR-TB.