Prapaporn SrilohasinTherdsak PrammanananKiatichai FaksriJody E. PhelanPrapat SuriyapholPhalin KamolwatSaijai SmithtikarnAreeya DisratthakitSanjib Mani RegmiManoon LeechawengwongsRick Twee-Hee OngYik Ying TeoSissades TongsimaTaane G. ClarkAngkana ChaiprasertLondon School of Hygiene & Tropical MedicineKhon Kaen UniversityNational University of SingaporeThailand Ministry of Public HealthThailand National Center for Genetic Engineering and BiotechnologyFaculty of Medicine, Siriraj Hospital, Mahidol UniversityVichaiyut HospitalThailand National Science and Technology Development AgencyGandaki Medical College Teaching HospitalSiriraj Foundation2020-12-282020-12-282020-01-01Emerging Microbes and Infections. Vol.9, No.1 (2020), 2632-2641222217512-s2.0-85097561954https://repository.li.mahidol.ac.th/handle/123456789/60503© 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group, on behalf of Shanghai Shangyixun Cultural Communication Co., Ltd. Tuberculosis disease (TB), caused by Mycobacterium tuberculosis, is a major public health issue in Thailand. The high prevalence of modern Beijing (Lineage 2.2.1) strains has been associated with multi- and extensively drug-resistant infections (MDR-, XDR-TB), complicating disease control. The impact of rarer proto-Beijing (L2.1) strains is less clear. In our study of thirty-seven L2.1 clinical isolates spanning thirteen years, we found a high prevalence of XDR-TB cases (32.4%). With ≤ 12 pairwise SNP distances, 43.2% of L2.1 patients belong to MDR-TB or XDR-TB transmission clusters suggesting a high level of clonal expansion across four Thai provinces. All XDR-TB (100%) were likely due to transmission rather than inadequate treatment. We found a 47 mutation signature and a partial deletion of the fadD14 gene in the circulating XDR-TB cluster, which can be used for surveillance of this rare and resilient M. tuberculosis strain-type that is causing increasing health burden. We also detected three novel deletion positions, a deletion of 1285 bp within desA3 (Rv3230c), large deletions in the plcB, plcA, and ppe38 gene which may play a role in the virulence, pathogenesis or evolution of the L2.1 strain-type.Mahidol UniversityImmunology and MicrobiologyArticleSCOPUS10.1080/22221751.2020.1852891