title: Evaluation of the GenoType® MTBDRsl assay for susceptibility testing of second-line anti-tuberculosis drugs.
abstract: BACKGROUND
  The GenoType® MTBDRsl assay is a new rapid assay for the detection of resistance to second-line anti-tuberculosis drugs.
  
  
  OBJECTIVE
  To evaluate the MTBDRsl assay on 342 multidrug-resistant tuberculosis isolates for resistance to ofloxacin (OFX), kanamycin  (KM), capreomycin (CPM) and ethambutol (EMB), to compare the results to the agar proportion method, and to test discrepant results using DNA sequencing.
  
  
  RESULTS
  The sensitivity and specificity of the MTBDRsl assay were respectively 70.3% and 97.7% for OFX, 25.0% and 98.7% for KM,  21.2% and 98.7% for CPM and 56.3% and 56.0% for EMB. DNA sequencing identified mutations that were not detected by the MTBDRsl assay. The 8/11 phenotypically OFX-resistant isolates had mutations in gyrA (2/8 had an additional mutation in the gyrB gene), 1/11 had mutations  only in the gyrB gene, 6/21 phenotypically KM-resistant isolates had mutations in the rrs gene, and 7/26 and 20/26 phenotypically CPM-resistant isolates had mutations in the rrs and tlyA genes.
  
  
  CONCLUSIONS
  The MTBDRsl assay showed lower sensitivity than  previous studies. The assay performed favourably for OFX; however, it was less sensitive in the detection of KM/CPM resistance and demonstrated low sensitivity and specificity for EMB resistance. It is recommended that the MTBDRsl assay include additional genes to achieve better sensitivity  for all the drugs tested.
authors.affiliation: Department of Medical Microbiology, Faculty of Health Science, University of Pretoria, Pretoria, South Africa. ahlammdd@yahoo.com
authors.forename: H M
authors.initials: HM
authors.lastname: Said
authors.forename: M M
authors.initials: MM
authors.lastname: Kock
authors.forename: N A
authors.initials: NA
authors.lastname: Ismail
authors.forename: K
authors.initials: K
authors.lastname: Baba
authors.forename: S V
authors.initials: SV
authors.lastname: Omar
authors.forename: A G
authors.initials: AG
authors.lastname: Osman
authors.forename: A A
authors.initials: AA
authors.lastname: Hoosen
authors.forename: M M
authors.initials: MM
authors.lastname: Ehlers
mesh_terms: D000995:Antitubercular Agents / Q000627:therapeutic use*; D001426:Bacterial Proteins / Q000235:genetics*; D002207:Capreomycin / Q000627:therapeutic use; D027081:DNA Gyrase / Q000235:genetics; D004252:DNA Mutational Analysis; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004977:Ethambutol / Q000627:therapeutic use; D005838:Genotype; D006801:Humans; D007612:Kanamycin / Q000627:therapeutic use; D007613:Kanamycin Resistance / Q000235:genetics; D008826:Microbial Sensitivity Tests / Q000379:methods; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D015242:Ofloxacin / Q000627:therapeutic use; D010430:Pentosyltransferases / Q000235:genetics; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012680:Sensitivity and Specificity; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D002207:Capreomycin; D007612:Kanamycin; D004977:Ethambutol; D015242:Ofloxacin; C540269:EmbB protein, Mycobacterium tuberculosis; D010430:Pentosyltransferases; D027081:DNA Gyrase