Primary Drug Resistance and Molecular Epidemiology of Mycobacterium tuberculosis Isolates from Patients in a Population with High Tuberculosis Incidence in Turkey

To determine the rate of primary drug resistance and compare the fingerprint pattern diversity of the resistant and sensitive Mycobacterium tuberculosis isolates, antituberculosis susceptibility testing and restriction fragment length polymorphism (RFLP) analysis were performed on 88 M. tuberculosis isolates of the patients who were diagnosed as new tuberculosis cases in 2000. Primary resistance to isoniazid, rifampicin, ethambutol, and streptomycin were determined by the BACTEC method. IS6110 and pTBN12 were used as molecular markers. The frequency of resistance to at least one drug was 32.95%, whereas 10.23% of the isolates were resistant to more than one drug. Single-drug resistance to isoniazid, streptomycin, ethambutol, and rifampicin was found in 9 (10.22%), 7 (7.95%), 4 (4.54%), and 0 (0.0%) strains, respectively. Two M. tuberculosis strains (2.26%) showed multiple drug resistance. The combination of two fingerprinting procedures on a total of 88 isolates identified 58 (65.9%) strains as unique and clustered 30 strains in 11 clusters (clustering = 34.1%). The clustering rate for resistant and sensitive isolates was 13.8% and 40.1%, respectively. In conclusion; drug susceptibility testing showed that the majority of the drug-resistant infections involved either isoniazid or streptomycin alone. In addition to the high tuberculosis incidence, elevated primary drug resistance and high clustering rate indicate problems in the present control programs. New control strategies supported by molecular typing might be more effective to reduce tuberculosis.