title: Comparative evaluation of Löwenstein-Jensen proportion method, BacT/ALERT 3D system, and enzymatic pyrazinamidase assay for pyrazinamide susceptibility testing of Mycobacterium tuberculosis.
abstract: Pyrazinamide (PZA) is an important first-line antituberculosis drug because of its sterilizing activity against semidormant tubercle bacilli. In spite of its very high in vivo activity, its in vitro activity is not apparent unless an acidic environment is available, which makes PZA susceptibility testing difficult by conventional methods. The present study was, therefore, planned to assess the performance of the colorimetric BacT/ALERT 3D system and compare the results with those from conventional tests, i.e., the Löwenstein-Jensen (LJ) proportion method (pH 4.85) and Wayne's pyrazinamidase (PZase) assay, using 107 clinical isolates. The concordance among all of these tests was 89.71% after the first round of testing and reached 92.52% after resolution of the discordant results by retesting. Prolonged incubation of the PZase tube for up to 10 days was found to increase the specificity of the PZase test. The concordances between LJ proportion and BacT/ALERT 3D, LJ proportion and the PZase assay, and BacT/ALERT 3D and the PZase assay were found to be 99.06%, 93.46%, and 92.52%, respectively. Using the LJ results as the gold standard, the sensitivities of BacT/ALERT 3D and the PZase assay were 100 and 82.85%, respectively, while the specificity was 98.61% for both of the tests. The difference between the sensitivities of BacT/ALERT 3D and the PZase assay was significant (P = 0.025). The mean turnaround times for the detection of resistant and susceptible results by BacT/ALERT 3D were 8.04 and 11.32 days, respectively. While the major limitations associated with the PZase assay and the LJ proportion method are lower sensitivity in previously treated patients and a longer time requirement, respectively, the BacT/ALERT 3D system was found to be rapid, highly sensitive, and specific.
authors.affiliation: Department of Microbiology and Molecular Biology, National JALMA Institute for Leprosy and Other Mycobacterial Diseases (ICMR), Tajganj, Agra (Uttar Pradesh) 282001, India.
authors.forename: Pushpendra
authors.initials: P
authors.lastname: Singh
authors.forename: Clement
authors.initials: C
authors.lastname: Wesley
authors.forename: G P S
authors.initials: GP
authors.lastname: Jadaun
authors.forename: Sunil Kumar
authors.initials: SK
authors.lastname: Malonia
authors.forename: R
authors.initials: R
authors.lastname: Das
authors.forename: P
authors.initials: P
authors.lastname: Upadhyay
authors.forename: J
authors.initials: J
authors.lastname: Faujdar
authors.forename: P
authors.initials: P
authors.lastname: Sharma
authors.forename: P
authors.initials: P
authors.lastname: Gupta
authors.forename: Abhay Kumar
authors.initials: AK
authors.lastname: Mishra
authors.forename: Kalpana
authors.initials: K
authors.lastname: Singh
authors.forename: D S
authors.initials: DS
authors.lastname: Chauhan
authors.forename: V D
authors.initials: VD
authors.lastname: Sharma
authors.forename: U D
authors.initials: UD
authors.lastname: Gupta
authors.forename: K
authors.initials: K
authors.lastname: Venkatesan
authors.forename: V M
authors.initials: VM
authors.lastname: Katoch
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism*; D000995:Antitubercular Agents / Q000494:pharmacology*; D003470:Culture Media; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000201:enzymology; D011237:Predictive Value of Tests; D011718:Pyrazinamide / Q000494:pharmacology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000995:Antitubercular Agents; D003470:Culture Media; D011718:Pyrazinamide; D000581:Amidohydrolases; C022490:pyrazinamide deamidase