Primary drug resistance to anti-tuberculous drugs in Karachi.

Objective: To assess the frequency of primary drug resistance among newly diagnosed tuberculosis cases in Karachi.
Study Design: Cross-sectional study.
Place and Duration of Study: Multicentric study involving various TB clinics and treatment centres of Karachi between April to December 2005.
Methodology: The frequency of drug resistance among new TB patients was evaluated using a non-probability convenient sampling methodology. Sputum sample was obtained from 140 newly diagnosed sputum smear-positive patients of pulmonary tuberculosis from various centres of Karachi. Sensitivities were performed by proportion method.
Results: Fifteen (11.5%) samples in 130 eligible patients showed primary resistance to one or more drugs. Ten (7.6%) of the isolates tested were resistant to a single drug, none were resistant to 2 drugs, 4 (3.0%) to 3 drugs and 1 (0.76%) to 4 drugs while 1 (0.76%) to all 5 first line agents. Resistance to streptomycin (10 microg/ml) was seen in 8 (6.1%), isoniazid (1microg/ml) in 12 (9.2%), Rifampicin (5 microg/ml) in 4 (3.0%), ethambutol (10 microg/ml) in 1 (0.76%) and pyrazinamide in 6 (4.6%) samples. Primary Multi-Drug Resistance (PMDR) was found in 2 (1.5%) patients. (Isoniazid 1 microg/ml, rifampicin 5 microg/ml with or without other drugs).
Conclusion: In the studied patients, primary drug resistance to at least one anti-tuberculosis drug was 11.5%. It requires an efficiently working anti-tuberculosis programme to prevent escalation including resistance.