Pattern of mycobacterial resistance to four anti-tuberculosis drugs in pulmonary tuberculosis patients in the state of Qatar after the implementation of DOTS and a limited expatriate screening programme.

OBJECTIVE: To determine the resistance pattern of Mycobacterium tuberculosis to four anti-tuberculosis drugs in pulmonary tuberculosis patients in the State of Qatar after the implementation of DOTS and an expatriate screening programme on arrival.

METHOD: A state-wide, population-based, retrospective analysis of all cases of pulmonary tuberculosis with positive M. tuberculosis culture reported to the Division of Public Health TB Unit from January 1996 to December 1998. M. tuberculosis sensitivity testing was done by the Bactec method for isoniazid (INH), rifampicin (RMP), streptomycin (SM) and ethambutol (EMB). The results were interpreted as a daily change of the growth index of test vials (with drug) compared with controls.

RESULTS: There were 406 isolates with positive M. tuberculosis culture. Sixty-one (15%) were resistant to one or more of the four anti-tuberculosis drugs, of which 58 (95%) were from newly diagnosed cases (primary) and three (5%) were from previously treated cases (acquired). Primary resistance was as follows: any resistance 15%, INH 12.4%, RMP 2%, SM 5.2%, EMB 0.8% and multidrug resistance (MDR, resistance to INH and RMP at least) was found in 0.8%. Acquired resistance was as follows: any resistance 15%, INH 15%, RMP 5%, SM 5% and MDR 5%.

CONCLUSION: The prevalence of resistance to four anti-tuberculosis drugs is strikingly low due to the limited expatriate screening programme (chest radiography) and implementation of DOTS. The four-drug regimen is recommended for the initial phase of therapy until the results of sensitivity testing are known.