Discrepant Results Between Pyrazinamide Susceptibility Testing by the Reference BACTEC 460TB Method and

摘要

Background: Mycobacterium tuberculosis strains belonging to theW-Beijing family have receivednbroad clinical and public health attention because of their rapid worldwide spread and theirnfrequent association with outbreaks, multidrug resistance, and treatment failures and relapses.nMethods: The present study examined a large number of multidrug-resistant strain-W isolatesn(isolates of 29 patients) by susceptibility testing for pyrazinamide (PZA) using the referencenBACTEC 460TB method (Becton Dickinson Diagnostic Instrument Systems; Sparks, MD) andnalso by DNA sequencing of the pncA gene.nResults: We found that despite of the presence of a strain W-specific Thr47Ala in the pncA gene,nall strains showed susceptibility to PZA in the reference BACTEC 460TB system due to theirnhigher minimum inhibitory concentrations (relative to BACTEC 460TB PZA-susceptible strains).nConclusions: Our results suggest that the current radiometric reference method cannot repro-nducibly detect PZA resistance in patients infected with W-Beijing strains. Therefore, PZAnsusceptibility testing should instead be based on analysis of the pncA gene for resistance-nassociated mutations.