Comparison between antibiotic susceptibility testing and pyrosequencing analysis for the detection of rifampicin and isoniazid resistant tuberculosis

Tuberculosis is a global public health problem. The development of drug-resistant tuberculosis had made the problem even worse. The increase in the frequency of drug resistant Mycobacterium tuberculosis requires an early, efficient and reliable detecting analysis to improve the treatment and reduce the spread of resistant tuberculosis. Molecular methods are promising for the rapid detection of Mycobacterium tuberculosis drug resistance. We investigated the role of pyrosequencing for the detection of rifampicin and isoniazid resistance in 49 Mycobacterium tuberculosis isolates in mycobacterial lab of Gaziantep University for the period between January 2013 and April 2014. MGIT system showed that 37 isolates were susceptible to both INH and RIF, 11 isolates were mono-resistant (one resistant to only RIF and 10 resistant to only INH), and one isolate was resistant to both RIF and INH. By pyrosequencing, 2 rifampicin resistant isolates by MGIT had no mutation in the rifampicin resistance determining gene (RRDR) of the rpoB gene, and 3 of the rifampicin-susceptible isolates had mutations at the RRDR. Regarding isoniazid, pyrosequencing had found that only one of the 11 isoniazid-resistant isolates by MGIT system had mutation in the katG gene, and one of the phenotypically isoniazid-susceptible isolate had mutation in the katG gene. Pyrosequencing technique has the advantage of providing the results of rifampicin and isoniazid resistant Mycobacterium tuberculosis isolates within a short time, but on the other hand, it is expensive, and in order to give a resistance decision, several genes that are associated with the drug resistance must be studied. Key Words: Mycobacterium tuberculosis, rifampicin, isoniazid, pyrosequencing.