Genotypic diversity of multidrug-, quinolone- and extensively drug-resistant Mycobacterium tuberculosis isolates in Thailand

Abstract

Drug-resistant tuberculosis (TB), which includes multidrug-resistant (MDR-TB), quinolone-resistant (QR-TB) and extensively drug-resistant tuberculosis (XDR-TB), is a serious threat to TB control. We aimed to characterize the genotypic diversity of drug-resistant TB clinical isolates collected in Thailand to establish whether the emergence of drug-resistant TB is attributable to transmitted resistance or acquired resistance. We constructed the first molecular phylogeny of MDR-TB (n=95), QR-TB (n=69) and XDR-TB (n=28) in Thailand based on spoligotyping and proposed 24-locus multilocus variable-number of tandem repeat analysis (MLVA). Clustering analysis was performed using the unweighted pair group method with arithmetic mean. Spoligotyping identified the Beijing strain (SIT1) as the most predominant genotype (n=139; 72.4%). The discriminatory power of 0.9235 Hunter-Gaston Discriminatory Index (HGDI) with the 15-locus variable-number tandem repeats of mycobacterial interspersed repetitive units typing was improved to a 0.9574 HGDI with proposed 24-locus MLVA, thereby resulting in the subdivision of a large cluster of Beijing strains (SIT1) into 17 subclusters. We identified the spread of drug-resistant TB clones caused by three different MLVA types in the Beijing strain (SIT1) and a specific clone of XDR-TB caused by a rare genotype, the Manu-ancestor strain (SIT523). Overall, 49.5% of all isolates were clustered. These findings suggest that a remarkable transmission of drug-resistant TB occurred in Thailand. The remaining 50% of drug-resistant TB isolates were unique genotypes, which may have arisen from the individual acquisition of drug resistance. Our results suggest that transmitted and acquired resistance have played an equal role in the emergence of drug-resistant TB. Further characterization of whole genome sequences of clonal strains could help to elucidate the mycobacterial genetic factors relevant for drug resistance, transmissibility and virulence.

Role of gyrB Mutations in Pre-extensively and Extensively Drug-Resistant Tuberculosis in Thai Clinical Isolates

“…b QS, quinolone susceptible; QR, quinolone resistant. c Data are from a previous study (27). d ND, not demonstrated in a previous report.…”

“…Therefore, additional analysis may be needed to determine the unclarified roles of these mutations in quinolone resistance (18)(19)(20)(21). In addition, one synonymous mutation, GyrB-E87E, may be a potential genetic marker for the Manu-ancestor clade (Spoligo-International-Type 523), which is a rare genotype causing the clonal spread of XDR-TB in western Thailand (27,49).…”

“…Spoligotyping was performed as a part of our prior study (27) using a spoligotyping kit (Ocimum Biosolution, Hyderabad, India) (28). Gyrase mutation data and spoligotyping information were analyzed together to rule out mutations that may have represented lineage-specific mutations that were not involved in quinolone resistance.…”

Methodological and Clinical Aspects of the Molecular Epidemiology of Mycobacterium tuberculosis and Other Mycobacteria

“…In a recent study in Thailand, 72% of 192 isolates collected were of the Beijing genotype. There, 49.5% of all MDR TB isolates were clustered, suggesting active transmission (499). In a small-scale study in Japan, of 55 isolates in 2002, 62% (n ϭ 34) proved to belong to the Beijing genotype, and 13% (n ϭ 7) belonged to the T genotype family (500).…”

Determining the risk of intra-community transmission of tuberculosis in the northwest of Iran through 15 loci MIRU-VNTR typing

“…MIRU-VNTR analysis has the potential to become more discriminative, especially by utilizing additional loci. The addition of more loci increases the number of patterns observed in the sets [11]. …”