Background: Drug-resistant mycobacterium tuberculosis isolates are a major public health concern worldwide. Multidrug resistant tuberculosis (MDR-TB) is a threat to tuberculosis control programmes.
Objectives: This study was conducted to evaluate the drug resistance patterns of mycobacterium tuberculosis and To assess risk factors for drug-resistant TB (including multidrug-resistance (MDR-TB).
Methods: The drug resistance patterns of 80 mycobacterium tuberculosis isolates from pulmonary tuberculosis (PTB) cases were investigated between January 2008 to June 2009. Drug susceptibility testing against rifampin (RIF), isoniazid (INB), streptomycin (SM), ethambutol (EMB), and pyrazinamide (PZA) was performed using the agar proportional method.
Results: Of 82 patients, including 61 males and 21 females, 81.7% of patients were younger than 50 years. Susceptibility to all five drugs was found in 66.3% and drug resistance in 33.8 (27 of 80) 11.5% (6 of 52) of new and 75% (21 of 28) of retreatment cases and multidrug resistance in 13.8% (11of 80) 3.9% (2 of 52) & 32.1% (9 of 28) of the new & retreated cases respectively. Monoresistance was found in 10% of the cases. Three of the 11 isolated (3.8%) showing multidrug resistance were resistant to all four drugs. These findings are critical and the risk to public health is high, particularly with an overall multidrug resistance of 13.8%. The resistance rates were 22.5% for rifampicin, 20% for isoniazid, 17.5 % for ethambutol, 13.8% for streptomycin and 1.3% for pyrazinamide. The highest resistance rates were found to rifampicin (22.5% overall; and 53.6% among previously treated patients). Drug resistant isolates were significantly higher among previously treated patients 75% than new cases 11.1% (P˂0.0001), also with far advanced disease (P˂0.004). Drug resistance rates were significantly higher in age groups less than 50 years old (81.5%), compared to those of more than 50 years old (18.5%) (P˂0.05). Risk factors for drug resistance TB (MDR-TB) included: being a retreatment cases (77.7%), diabetes mellitus (26%), rural areas (74.1%), no formal education (59.3%), for advanced disease (59.3%) and male gender (81.5%). A history of previous anti-TB therapy was a significant factor for overall drug resistance and MDR-TB.
Conclusion: Drug resistant TB including MDR-TB has been a major challenge for TB control. Prevention and control of drug-resistant TB should be emphasized by the revised DOTS (direct observed therapy, short course) program through prompt case detection, routine and quality assured drug susceptibility test for patients at high risk of resistance, programmatic treatment with both first and second-line medicines, and systematic treatment observation, with priority for high MDR-TB settings.