Molecular identification and characterization of rifampicin-resistant Mycobacterium tuberculosis isolates by line probe assay:: an approach for rapid diagnosis of multidrug-resistant tuberculosis

Aim: Early identification and characterization of rifampicin-resistant (R-r) Mycobacterium tuberculosis isolates recovered from the samples of tuberculosis (TB) patients in the Aegean (West Anatolian) Region was intended. Methods and Results: Sixty isolates [47 (78.3%) multidrug-resistant (MDR)], which were identified as M. tuberculosis complex and phenotypically resistant to rifampicin by both BACTEC mycobacteria growth indicator tube (MGIT) 960 and 460 systems were analysed by a commercial line probe assay (INNO-LiPA Rif TB). The concordance of LiPA with the in vitro susceptibility test was found as 98.3%. Among the isolates, S531L (R5 pattern; 46.7%) and L511P/R, S512T, Q513L/K (Delta S1 pattern; 11.7%) were the most frequent mutation patterns. As compared with the BACTEC systems and conventional techniques for cultivation, identification and in vitro susceptibility testing, INNO-LiPA Rif TB after cultivation in BACTEC MGIT 960 system provided an average of 20 days early diagnosis of (RM)-M-r. tuberculosis isolates. Conclusions: Rapid molecular identification and characterization of (RM)-M-r. tuberculosis isolates after BACTEC MGIT 960 cultivation would be useful for faster diagnosis, infection control and planning of accurate treatment in MDR-TB patients. Significance and Impact of the Study: Patients with MDR-TB need a specified treatment and efficient follow-up strategies. Rapid and practical methodologies to diagnose and follow these patients should be applied in routine use.