title: Clonal expansion of Mycobacterium tuberculosis isolates and coexisting drug resistance in patients newly diagnosed with pulmonary tuberculosis in Hanoi, Vietnam.
abstract: BACKGROUND
  Newly diagnosed patients without anti-tuberculosis (TB) treatment histories have not often undergone drug susceptibility testing (DST), but have received the standard treatment regimen without information about their DST profiles in many countries with inadequate resources.
  
  
  METHODS
  We collected 346 clinical isolates from previously untreated patients with smear-positive active TB in Hanoi, the capital of Vietnam. Of these, 339 were tested for susceptibility to four first-line anti-TB drugs, including isoniazid (INH), rifampicin (RMP), streptomycin (SM), and ethambutol (EMB), using the proportion method. A pyrazinamidase (PZase) test was used to assess pyrazinamide (PZA) resistance. Results of the culture-based drug susceptibility tests were confirmed by those from reverse hybridization-based line probe assays (LiPAs) that detected mutations associated with RMP, INH, PZA, and fluoroquinolone (FQ) resistance. To investigate a diversity of these strains, IS6110-probed restriction fragment length polymorphisms (RFLPs) were analyzed. Nucleotide sequences for furA-katG and fabG1-inhA operons, transcription units responsible for INH resistance, were also determined.
  
  
  RESULTS
  Of the isolates tested, 127 (37.5%) were resistant to at least one of the four drugs, which included 93 (27.4%) isolates that were resistant to INH. RFLP analysis identified four clusters defined by similarity of the band patterns, which accounted for 46.1% of the tested isolates. Among the clustered isolates, 37.7% were resistant to INH, most of which (85.4%) carried a g944c mutation, which causes an S315T amino acid substitution, in the katG gene.
  
  
  CONCLUSIONS
  Our results suggest that drug-resistant strains, particularly those with INH resistance characterized by a single mutation, S315T, are spreading in Hanoi, Vietnam. When RMP resistance is combined with this setting, patients are not easily cured by conventional short-term treatment. We will need to carefully monitor these trends and search for the origins and transmission routes of these strains.
authors.affiliation: Department of Microbiology, National Lung Hospital, 463 Hoang Hoa Tham, Hanoi, Vietnam. hungmtb75@gmail.com.
authors.forename: Nguyen Van
authors.initials: NV
authors.lastname: Hung
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ando
authors.forename: Tran Thi-Bich
authors.initials: TT
authors.lastname: Thuy
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kuwahara
authors.forename: Nguyen Thi-Le
authors.initials: NT
authors.lastname: Hang
authors.forename: Shinsaku
authors.initials: S
authors.lastname: Sakurada
authors.forename: Pham Huu
authors.initials: PH
authors.lastname: Thuong
authors.forename: Luu Thi
authors.initials: LT
authors.lastname: Lien
authors.forename: Naoto
authors.initials: N
authors.lastname: Keicho
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000995:Antitubercular Agents / Q000627:therapeutic use*; D002999:Clone Cells; D004269:DNA, Bacterial / Q000145:classification / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects / Q000235:genetics*; D004977:Ethambutol / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007538:Isoniazid / Q000627:therapeutic use; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D009876:Operon; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D011718:Pyrazinamide / Q000627:therapeutic use; D012293:Rifampin / Q000627:therapeutic use; D013307:Streptomycin / Q000627:therapeutic use; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D014744:Vietnam / Q000453:epidemiology
chemical_list: D000995:Antitubercular Agents; D004269:DNA, Bacterial; D011718:Pyrazinamide; D004977:Ethambutol; D007538:Isoniazid; D012293:Rifampin; D013307:Streptomycin