title: Validation of pncA gene sequencing in combination with the mycobacterial growth indicator tube method to test susceptibility of Mycobacterium tuberculosis to pyrazinamide.
abstract: Pyrazinamide is important in the treatment of tuberculosis. Unfortunately, the diagnosis of pyrazinamide resistance is hampered by technical difficulties. We hypothesized that mutation analysis combined with the mycobacterial growth indicator tube (MGIT) phenotypic method would be a good predictor of pyrazinamide resistance. We prospectively analyzed 1,650 M. tuberculosis isolates referred to our tuberculosis reference laboratory in 2008 and 2009. In our laboratory, the MGIT 960 system was used for pyrazinamide resistance screening. If a pyrazinamide-resistant strain was detected, we performed a pncA gene mutation analysis. A second MGIT 960 susceptibility assay was performed afterwards to evaluate the accuracy of the pncA mutation analysis to detect true- or false-positive MGIT results. We observed pyrazinamide resistance in 69 samples using the first MGIT 960 analysis. In a second MGIT 960 analysis, 47 of the 69 samples proved susceptible (68% false positivity). Sensitivity of nonsynonymous pncA mutations for detecting resistant isolates was 73% (95% confidence interval [CI], 61% to 73%), and specificity was 100% (95% CI, 95% to 100%). A diagnostic algorithm incorporating phenotypic and molecular methods would have a 100% positive predictive value for detecting pyrazinamide-resistant isolates, indicating that such an algorithm, based on both methods, is a good predictor for pyrazinamide resistance in routine diagnostics.
authors.affiliation: Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. s.simons@long.umcn.nl
authors.forename: Sami O
authors.initials: SO
authors.lastname: Simons
authors.forename: Jakko
authors.initials: J
authors.lastname: van Ingen
authors.forename: Tridia
authors.initials: T
authors.lastname: van der Laan
authors.forename: Arnout
authors.initials: A
authors.lastname: Mulder
authors.forename: P N Richard
authors.initials: PN
authors.lastname: Dekhuijzen
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Boeree
authors.forename: Dick
authors.initials: D
authors.lastname: van Soolingen
mesh_terms: D000293:Adolescent; D000328:Adult; D000369:Aged, 80 and over; D000581:Amidohydrolases / Q000235:genetics*; D000995:Antitubercular Agents / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D011718:Pyrazinamide / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods; D014376:Tuberculosis / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D011718:Pyrazinamide; D000581:Amidohydrolases; C487496:PncA protein, Mycobacterium tuberculosis
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