Narmandakh, Erdenegerel

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Age-stratified prevalence of latent tuberculosis infection in Ulaanbaatar, Mongolia: a facility-based cross-sectional study
(2026-09)
Narmandakh, Erdenegerel
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Tumur, Enkhtsetseg
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Sharkhuu, Gundsuren
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Igarashi, Yuriko
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Ganbaatar, Gantungalag
OBJECTIVES: Mongolia has a high tuberculosis (TB) burden. This study aimed to assess the age-specific latent TB infection (LTBI) prevalence in a healthy population in Mongolia by using interferon-gamma release assays. METHODS: This facility-based cross-sectional study was conducted from June 2024 to March 2025 in Ulaanbaatar. Eligible participants were asymptomatic, aged ≥10 years, had no previous TB treatment, and had no known contact with TB. LTBI was detected using the QuantiFERON-TB Gold Plus (QFT-Plus) assay. Sociodemographic data were collected using standardized questionnaires. RESULTS: The overall QFT-Plus positivity rate in 766 eligible participants (mean age: 38.2 years; 47.1% female) was 33.4%. Age-specific positivity increased from 7.9% (participants aged 10-19 years) to 46.1% (participants aged ≥60 years, P < 0.0001). Sex was not associated with positivity (P = 0.652), although the rate was slightly higher in women aged 40-59 years than in men. Multivariable analysis confirmed that age was a significant predictor of QFT-Plus positivity, reflecting TB prevalence. CONCLUSION: Ulaanbaatar's LTBI prevalence remains high, especially among older adults, suggesting a shift from recent transmission to remote infection reactivation. Although QFT-Plus positivity in young individuals remains high, our findings support the prioritization of targeted preventive strategies for older populations.
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Genetic Mutations Associated with Isoniazid Resistance in Mycobacterium tuberculosis in Mongolia
(2020-06)
Narmandakh, Erdenegerel
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Tumenbayar, Oyuntuya
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Borolzoi, Tsetsegtuya
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Erkhembayar, Baasansuren
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Boldoo, Tsolmon
Globally, mutations in the katG gene account for the majority of isoniazid-resistant strains of Mycobacterium tuberculosis Buyankhishig et al. analyzed a limited number of Mycobacterium tuberculosis strains in Mongolia and found that isoniazid resistance was mainly attributable to inhA mutations (B. Buyankhishig, T. Oyuntuya, B. Tserelmaa, J. Sarantuya, et al., Int J Mycobacteriol 1:40-44, 2012, https://doi.org/10.1016/j.ijmyco.2012.01.007). The GenoType MTBDRplus assay was performed for isolates collected in the First National Tuberculosis Prevalence Survey and the Third Anti-Tuberculosis Drug Resistance Survey to investigate genetic mutations associated with isoniazid resistance in Mycobacterium tuberculosis in Mongolia. Of the 409 isoniazid-resistant isolates detected by the GenoType MTBDRplus assay, 127 (31.1%) were resistant to rifampin, 294 (71.9%) had inhA mutations without katG mutations, 113 (27.6%) had katG mutations without inhA mutations, and 2 (0.5%) had mutations in both the inhA and katG genes. Of the 115 strains with any katG mutation, 114 (99.1%) had mutations in codon 315 (S315T). Of the 296 strains with any inhA mutation, 290 (98.0%) had a C15T mutation. The proportions of isoniazid-resistant strains with katG mutations were 25.3% among new cases and 36.2% among retreatment cases (P = 0.03) and 17.0% among rifampin-susceptible strains and 52.8% among rifampin-resistant strains (P < 0.01). Rifampin resistance was significantly associated with the katG mutation (adjusted odds ratio, 5.36; 95% confidence interval [CI], 3.3 to 8.67, P < 0.001). Mutations in inhA predominated in isoniazid-resistant tuberculosis in Mongolia. However, the proportion of katG mutations in isolates from previously treated cases was higher than in those from new cases, and the proportion in cases with rifampin resistance was higher than in cases without rifampin resistance.
Scopus© Citations 11

Narmandakh, Erdenegerel

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