Primary Resistance of Mycobacterium Tuberculosis to Isoniazid, Streptomycin, Rifampin, and Ethambutol in Pulmonary Tuberculosis

Background-Paucity of information about primary drug resistance in this region and the necessity of obtaining information due to worldwide emergence of multidrug resistance tuberculosis (MDR-TB) prompted this study.Methods-A total of 165 specimens from cases with pulmonary tuberculosis were selected in 3 consecutive years by the non-probable convenience method. This sample included about 1/3 of all sputum/washing-positive pulmonary tuberculosis (TB) cases. Direct microscopy we used according to the "International Union against Tuberculosis and Lung Disease" (IUATLD) guideline; for culture, isolation and sensitivity test we applied the WHO guideline in order to compare our results with those of national and international studies on primary drug resistance. Relapse cases or patients with previous history of anti-TB treatment and mycobacteria other than Mycobacterium tuberculosis (including Mycobacterium bovis) were excluded from the study by careful enquiry of records and laboratory data.Results-Seventeen cases were excluded from the study and the remaining 148 had the clinical and laboratory criteria of primary drug resistance. Mean age of the patients was 44.01±18.23 and 56% were males. All patients had clinicoradiological findings of pulmonary tuberculosis. Single primary drug resistance to isoniazid (INH) and streptomycin (SM) were 4.05 % and 8.78 % and total primary resistance were 7.43% and 12.83 % respectively. Combined resistance to INH+SM was seen in 3.38% of cases, and no resistance was detected to rifampin (RMP) and ethambutol (ETB) amongst new patients affected by Mycobacterium tuberculosis. Resistance to RMP and ETB was noticed only in patients with a previous history of anti-TB therapy (secondary resistance) or in patients with non-tuberculous mycobacteria. Conclusion-In this study which was conducted on patients with pulmonary TB, the highest primary resistance was towards SM and INH alone or to both of these drugs. There was no primary resistance to RMP or ETB, and hence the possibility of MDR-TB is negligible in our region.