Investigation of rpoB gene mutations causing Rifamisin resistance by DNA sequencing analysis in patients with pulmonary and extrapulmonary tuberculosis

Although the use of the effective drugs in the treatment of tuberculosis which is one of the oldest diseases in history, nowadays the main reasons of the failure of tuberculosis treatments are the false treatment protocols and the development of drug resistance.The drug resistance in tuberculosis is a major public health problem in our country as in the world. It may occur whether as a result of false treatment or the contamination of the infection through resistant patients to people around them.Rifampicin (RIF) and isoniacid (INH) are the primary and most effective drugs used in the treatment of tuberculosis. Approximately 90 % of RIF-resistant cases also show resistance to INH. Because of this reason RIF-resistance is also defined as multi-drug resistance.In this study, DNA isolations were performed from cultures of the 30 patients [(20 males (66,66%) and 10 females (33,33%)] whose direct microscopies and cultures were positive. After DNA was obtained, base sequences were determined by DNA sequence analysis. Our data were compared with the international gene bank data cancerning base sequences which are responsible for rifampicin resistance. According to these data mutations causing rifampicin resistance occur between the codons of 507 and 533. In our study, in 2 of 30 cases (66,66%) mutations related rifampicin resistance were identified. One mutation was in 531th codon (TCG(ser) TTG(leu)/aminoacid change) and the other was in 526th codon (CAC(His) TAC (Tyr) / amino acid change). As we compare our rifampicin resistance ratio (6,66%) with other studies in Turkey, our result seems to be lower. The reason of the lowest resistance ration in our study is thougt to be the patients inclueded who all have primary tuberculosis.Molecular methods are important for rapid diagnosis and determination of drug resistance related to mutations. DNA sequence analysis which is one of the moleculer methods is thought to be useful in the identification of M.tuberculosis at the species level, in the determination of the effective treatment protocols and in rapid diagnosis of rifampicin resistant mutations. It will also contribute to new studies for the detection of MDR-TB cases that are believed to be widespread all over the world.