[Conventional and molecular diagnosis in a group of patients with drug-resistant tuberculosis].

Worldwide, although the incidence of the sensitive/susceptible tuberculosis diminished, the number of drug resistant tuberculosis is growing. The bacteriological diagnosis, genetic and phenotypic, becomes essential for the epidemic control. The resistance appears as a phenotypic expression of mutations from M. tuberculosis genome. The mutations that appear for Rifampicin are in region rpoB, for Isoniazid in region katG and inhA, for Ethambutol-embB, Quinolone-gyrA, Aminoglicozid and Cyclical Peptides-rrs. To follow the concordance of results of drug sensitivity test (DST) through phenotypic and genetic method, we analyzed a group of 40 patients with TB-DR. We performed drug susceptibility testing on Lowenstein-Jensen medium according to the instructions of the manufacturer. The strains were tested indirect genetic too, Genotype MTBDR plus forl INH and RIF and Genotype MTBDRsl for the second line drugs. The concordance between genetic method and the phenotypic method is 95%, 5% from the patients have different sensitivity to INH and RIF, butphenotypical they are resistant, meaning that they have other mutations undetected by the strip. The most common mutation in region rpoB is MUT3 (52%) associating the absence of band W8. Mutations in the region rpoB MUT1 and MUT2A are 12.5%, and 15% respectively. For high resistance to INH, the mostcommon isMUT1 forkatG 95% and forlow resistance to INHMUTI from region inhA-30%. For the second line drugs, the most frequent concordance between genetic method andphenotypic method is for EMB, of 30%, geneticallyspeaking the strains display no mutation in region embB, but are resistantin phenotypic method. For FQ, KAN, AMKand CAP the concordance between the two methods is of 100% to all tested strains. In conclusion, genetic methods have high sensitivity, they are fast and shorten significantly the diagnosis time.