Pattern of Drug Resistance in Pulmonary TB Patients

Tuberculosis is a common infectious disease these days; it has the highest mortality rate among all infectious causes only after HIV/AIDS. The emergence of tuberculous bacillus species resistant to multiple drugs has become a serious global threat to the human health. Drug resistance is either acquired with the initial infection (from a host harboring resistant tubercle bacilli) or develops during treatment with antituberculous chemotherapeutic agents because of poor patients compliance or inadequate/ inappropriate treatment regimens. This study has been done to evaluate drug resistance and to determine the type of resistance in drug resistant tuberculosis patients. The files of patients hospitalized during the past 2.5 years in Massih-Daneshvari clinical mycobacteriology ward due to suspected drug resistant tuberculosis were evaluated. Those who had a sputum antibiogram indicating resistance at least to one anti-TB drug were included in the study. Data, including demographic data, radiologic findings, sputum smear, sputum culture, and antibiogram were recorded in a specified questionnaire. Analysis was done for central indices using the SPSS software. Forty-three cases met the inclusion criteria. Twenty-seven (63%) were male and 16(37%) were female with the age range of 16-80 years (mean ±SD, 36.9 ±16.76). Twenty-five cases (58%) were Afghan and 13(30%) were Iranian (Other nationalities had not been recorded). Antibiograms of 38 patients (88%) showed resistance at least to isoniazid and rifampicin; these patients were considered as multidrug resistant (MDR) cases. In 24 cases (56%), the Mycobacterium tuberculosis was resistant to all four-drug isoniazid (INH), rifampicin (RIF), streptomycin (STM), and ethambutol (EMB). Thirty-six patients (85%) had resistance at least to STM, and 26 patients (60%) were resistant at least to EMB. Bacillus drug susceptibility to pirazinamide (PZA) was not specified. Most drug-resistant cases of TB were seen among Afghan emigrants. Ninety-five percent of cases had a history of treatment at least once, and the resistance was secondary (acquired). Despite discontinuation of streptomycin usage as an anti-TB drug in Iran in the recent years, the most common type of resistance was related to this drug, occurring in 85% of cases. Confirming different studies in other countries, the lowest resistance to the first line anti-TB drugs was for EMB, detected in 56% of cases. (Tanaffos 2003; 2(7): 47-51)