Influence of anti-tuberculosis drug resistance on the treatment outcome of pulmonary tuberculosis patients receiving DOTS in Riyadh, Saudi Arabia.

To determine the influence of anti-tuberculosis drug resistance existing prior to treatment on the outcome of pulmonary tuberculosis patients receiving standard short-course chemotherapy (SCC) under direct observation under national programme guidelines. Treatment outcomes of sputum smear- and culture-positive pulmonary tuberculosis patients admitted consecutively from 1998 through 1999 in a referral hospital in Riyadh, Saudi Arabia, were reviewed retrospectively. A total of 515 patients were reviewed; 139 patients were deported or transferred out. Treatment outcomes and follow-up for about 2 years were analysed for the remaining 376 patients. Among 315 patients with sensitive isolates, 301 achieved favourable outcome, none relapsed or failed, 10 defaulted, one died and three were lost to follow-up at 6 months. Mono-resistance to isoniazid, streptomycin or ethambutol did not influence the treatment outcome. All the 18 patients with mono-resistance to rifampicin were cured, but two relapsed later. Among 39 patients with any rifampicin resistance, 37 patients had favourable outcome and two failed treatment; three later relapsed. Among eight patients with MDR-TB, six had favourable outcome and two failed treatment; one later relapsed. Sputum smear conversion rates at the end of 3 months of treatment in patients with any rifampicin resistance or with multidrug resistance were inferior to those of patients with sensitive strains (89.8% vs. 96.3%, P = 0.016 and 80% vs. 96.3%, P = 0.008, respectively). Anti-tuberculosis drug resistance existing prior to treatment, especially rifampicin and multidrug resistance, has an adverse effect on treatment outcome, even with directly observed standard SCC under national programme guidelines.