Trends in Mycobacterium tuberculosis resistance, Pakistan, 1990–2007

SummaryObjectiveTo determine resistance trends including the emergence of extensive drug resistance (XDR) in Mycobacterium tuberculosis (MTB) isolates from Pakistan.MethodsThis was a retrospective analysis of MTB isolates (January 1990–June 2007) collected from the four provinces of Pakistan. Standard methods were used to isolate MTB. Susceptibility against rifampin, isoniazid, streptomycin, ethambutol, ethionamide, capreomycin, cycloserine, and ciprofloxacin was tested using the agar proportion method, while susceptibility to pyrazinamide was determined using BACTEC. Resistance over the study period was assessed using Chi-square for trend analysis.ResultsResistance in 15343 MTB isolates showed a steady increase over the study period; a significant trend of increasing resistance was noted in three of the four provinces included in the study. XDR-tuberculosis was first seen in 1998; to date 22 XDR cases have been documented. MTB resistance was significantly lower (p<0.001) in patients under 5 and over 60 years of age, and significantly higher in males than females (p<0.001). MTB resistance was also higher in pulmonary than extrapulmonary isolates (p