Genotypic characterization of multi-drug-resistant Mycobacterium tuberculosis isolates in Myanmar.

The number of multi-drug-resistant tuberculosis (MDR-TB) cases is rising worldwide. As a countermeasure against this situation, the implementation of rapid molecular tests to identify MDR-TB would be effective. To develop such tests, information on the frequency and distribution of mutations associating with phenotypic drug resistance in Mycobacterium tuberculosis is required in each country. During 2010, the common mutations in the rpoB, katG and inhA of 178 phenotypically MDR M. tuberculosis isolates collected by the National Tuberculosis Control Program (NTP) in Myanmar were investigated by DNA sequencing. Mutations affecting the 81-bp rifampicin (RIF) resistance-determining region (RRDR) of the rpoB were identified in 127 of 178 isolates (71.3%). Two of the most frequently affected codons were 531 and 526, with percentages of 48.3% and 14.0% respectively. For isoniazid (INH) resistance, 114 of 178 MDR-TB isolates (64.0%) had mutations in the katG in which a mutation-conferring amino acid substitution at codon 315 from Ser to Thr was the most common. Mutations in the inhA regulatory region were also detected in 20 (11.2%) isolates, with the majority at position -15. Distinct mutation rate and pattern from surrounding countries might suggest that MDR-TB has developed and spread domestically in Myanmar.

Insight into multidrug-resistant Beijing genotype Mycobacterium tuberculosis isolates in Myanmar.

OBJECTIVES: Myanmar is a World Health Organization high tuberculosis (TB) burden country with a high multidrug-resistant (MDR)-TB burden. Of significance, a high prevalence of the Beijing genotype of Mycobacterium tuberculosis (MTB) among MDR-MTB has been reported previously. A detailed genetic characterization of TB clinical isolates was performed in order to explore whether there is an association between the prevalence of the Beijing MTB genotype and MDR-TB in Myanmar. METHODS: A total of 265 MDR-MTB clinical isolates collected in 2010 and 2012 were subjected to spoligotyping, mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) analysis, single nucleotide polymorphism (SNP) typing, and drug resistance-associated gene sequencing, including rpoC to detect potential compensatory evolution. RESULTS: Of the total MDR-MTB isolates, 79.2% (210/265) were of the Beijing genotype, the majority of which were the 'modern' subtype. Beijing genotype isolates were differentiated by 15-locus MIRU-VNTR and a high clustering rate (53.0%) was observed in the modern subtype. These MIRU-VNTR patterns were similar to Beijing genotype clones spreading across Russia and Central Asia. A high prevalence of katG Ser315Thr, and genetic evidence of extensive drug resistance (XDR) and pre-XDR and compensatory mutations in rpoC were observed among clustered isolates. CONCLUSIONS: MDR-MTB strains of the Beijing genotype might be spreading in Myanmar and present a major challenge to TB control in this country.

FTA card utility for PCR detection of Mycobacterium leprae.

The suitability of the FTA® elute card for the collection of slit skin smear (SSS) samples for PCR detection of Mycobacterium leprae was evaluated. A total of 192 SSS leprosy samples, of bacillary index (BI) 1 to 5, were collected from patients attending two skin clinics in Myanmar and preserved using both FTA® elute cards and 70% ethanol tubes. To compare the efficacy of PCR detection of DNA from each BI class, PCR was performed to amplify an M. leprae-specific repetitive element. Of the 192 samples, 116 FTA® elute card and 112 70% ethanol samples were PCR positive for M. leprae DNA. When correlated with BI, area under the curve (AUC) values of the respective receiver-operating characteristic curves were similar for the FTA® elute card and ethanol collection methods (AUC=0.6). Taken together, our results indicate that the FTA® elute card, which enables the collection, transport, and archiving of clinical samples, is an attractive alternative to ethanol preservation for the detection of M. leprae DNA.