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A5540 - Genetic Determinants and Compensatory Mutations Associated with Transmission of Multi-Drug Resistant Mycobacterium Tuberculosis in Vietnam
Author Block: H. Q. Nguyen1, N. V. Nguyen2, H. V. Nguyen3, V. T. Nguyen4, A. Bañuls5; 1Biotechnology - Pharmacology, University of Science and Technology of Hanoi, Hanoi, Viet Nam, 2National Tuberculosis Control Program, Hanoi, Viet Nam, 3National Lung Hospital, Ha Noi, Viet Nam, 4National Institute of Hygiene and Epidemiology, Hanoi, Viet Nam, 5Institute of Research for Development (IRD), Montpellier, France.
Rationale: Today, we are facing a rapid spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) in the world. Vietnam is one of the high MDR-TB burden countries, but only 11% of the notified tuberculosis patients have tested drug susceptibility with rapid diagnostics at time of diagnosis. Thus, the undetected MDR-TB cases could contribute to the emergence and spread of drug-resistant Mycobacterium tuberculosis in the community. Objectives: This work aimed to determine mutations linked to drug resistance and to identify compensatory mutations associated with transmission of MDR M. tuberculosis strains by molecular analysis. Methods: One hundred seventy M. tuberculosis isolates resistant to either rifampicin or isoniazid were selected (MDR = 123). We performed DNA sequencing for 11 main genes associated with first- and second-line drug resistances for all isolates. Fitness-compensatory mutations of rifampicin and isoniazid resistant isolates were analyzed by sequencing of rpoA, rpoC and ahpC genes. The molecular genotyping was identified by Spoligotyping and 24-locus mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) methods. Statistical and phylogenetic analyses were also performed. Results: We detected high frequencies of mutations responsible for resistance to rifampicin (99.2%), isoniazid (97%) and fluoroquinolones (90%), but lower for other drugs. Mutations associated with high level of resistance and low fitness costs were dominant. The sensitivity and specificity values were over 97% for MDR prediction. We found 19/123 (15.4%) MDR isolates carried fitness-compensatory mutations in either the rpoA or rpoC genes. These compensatory mutations were mainly in rifampicin-resistant isolates with the rpoB531 (Ser-Leu) mutation. Phylogenetic analysis showed a high diversity of mutation patterns within molecular clusters, and compensatory mutations appeared in different genotypes. Conclusion: These data suggest that mutation-based diagnostic methods would be efficient for MDR and fluoroquinolone-resistance predictions in M. tuberculosis population in Vietnam. Nevertheless, the high diversity of drug-resistance mutation patterns plus fitness-compensatory mutations linked to distinct genotypes suggest various evolutionary trajectories lead to a successful spread of highly drug-resistant strains. Keywords: Compensatory mutation, drug resistance mutation, Mycobacterium tuberculosis, multidrug resistant, extensively drug-resistant, fitness cost.