oa Molecular Diagnosis and Vaccines - Drug resistant Mycobacterium tuberculosis In Qatar: comparison between the conventional and DNA-based methods
Early detection of drug resistance in Mycobacterium tuberculosis (M. tuberculosis) and Mycobacterium bovis (M. bovis) isolates is crucial for appropriate treatment to prevent the development of further resistance and the spread of resistant strains. The identification of resistance mutations enables the development of molecular tests, which may result in a reduction of turnaround times for susceptibility results to 1 to 2 days. The aim of this study was to estimate the rate of M. bovis within the M. tuberculosis complex (MTC) isolates from Qatar. A second goal was to identify drug resistance to isoniazid (INH), ethambutol (EMb), rifampin (RIF), and streptomycin (STR) by the BACTEC method and mutations in rpoB and katG genes associated with RIF and INH respectively by the Single Strand Conformational Polymorphism (SSCP) method. The study was conducted on 100 MTC isolates from pulmonary tuberculosis patients at Al-Rumela Hospital, Doha Qatar. An allele-specific PCR amplification method was used to differentiate M. tuberculosis from M. bovis cultures. All isolates were found to be M. tuberculosis, and none of them was M. bovis. The conventional drug susceptibility results indicated that only one (1%) isolate is multi drug resistant (MDR) (resistant to both INH and RIF). Drug resistance was demonstrated in 6, 3, 1, and 1 isolates for INH, STR, RIF and EMB respectively. On the other hand, mutation was detected in 4/6 and 1/1 of the INH and RIF resistant isolates respectively. Mutation in the rpoB gene was also detected in two RIF susceptible isolates. It is concluded that M. tuberculosis (not M. bovis) is the main causative agent of human tuberculosis in Qatar and that the rate of drug resistance in M. tuberculosis is very low compared to other countries. The SSCP is a rapid, relatively inexpensive and easy to perform technique.
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