title: Molecular and phenotypic characterisation of Mycobacterium tuberculosis resistant to anti-tuberculosis drugs.
abstract: METHODS
  Dr Cetrángolo Hospital, Buenos Aires, Argentina.
  
  
  OBJECTIVE
  To characterise drug-resistant (DR), multidrug-resistant (MDR-) and extensively drug-resistant (XDR-) Mycobacterium tuberculosis isolates, and identify their genetic profiles, drug resistance levels and resistance-conferring mutations.
  
  
  METHODS
  Phenotypic drug susceptibility testing methods were used to determine drug resistance profiles. Minimal inhibitory concentrations (MICs) of isoniazid (INH), rifampicin (RMP) and levofloxacin (LVX) from 169 DR tuberculosis (TB) isolates, 78 of them monoresistant to INH, 13 to RMP, 7 to LVX, and 71 MDR-TB, were determined. Multiplex allele-specific polymerase chain reaction and DNA sequencing were used to detect mutations in katG, rpoB and gyrA/B genes. Genotyping was performed using spoligotyping and insertion sequence 6110 restriction fragment length polymorphism.
  
  
  RESULTS
  In total, 38.9% of the INH-resistant (INH(R)) isolates had an MIC ≥ 32 g/ml; 61.3% of RMP-resistant (RMP(R)) isolates had an MIC ≥ 64 g/ml and 55.6% of the LVX-resistant (LVX(R)) isolates had an MIC 4 ≥ 16 g/ml. The main mutations found in INH(R) isolates were katG315 (53.7%) and inhAP-15 (25.5%), whereas in RMP(R) isolates the main mutations were rpoB531 (61.9%), followed by rpoB526 (16.7%). LVX(R) isolates showed mutations in gyrA94/90. Haarlem, LAM and T were the main spoligotyping families found. katG315 was mainly associated with Haarlem and LAM, whereas inhAP-15 was associated with T.
  
  
  CONCLUSIONS
  Several isolates showed an association between high INH(R) levels and katG mutation; others from the Haarlem family were prone to becoming MDR-TB and continue to circulate in the community.
authors.affiliation: Reference Laboratory of Tuberculosis Control Program of Buenos Aires Province, Dr Cetrángolo Hospital, Florida, Buenos Aires, Argentina. belen.imperiale@conicet.gov.ar
authors.forename: B R
authors.initials: BR
authors.lastname: Imperiale
authors.forename: M J
authors.initials: MJ
authors.lastname: Zumárraga
authors.forename: A B
authors.initials: AB
authors.lastname: Di Giulio
authors.forename: A A
authors.initials: AA
authors.lastname: Cataldi
authors.forename: N S
authors.initials: NS
authors.lastname: Morcillo
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001118:Argentina / Q000453:epidemiology; D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial; D024881:Drug Resistance, Bacterial; D054908:Extensively Drug-Resistant Tuberculosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D005838:Genotype; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology; D064704:Levofloxacin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012293:Rifampin / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D014376:Tuberculosis / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D004269:DNA, Bacterial; D064704:Levofloxacin; D007538:Isoniazid; D012293:Rifampin