I Bouzouita1, A M Cabibbe2, A Trovato2, H Draoui3, A Ghariani4, B Midouni1, L Essalah3, E Mehiri4, D M Cirillo2, L Slim-Saidi4. 1. National Reference Laboratory for Mycobacteria, Unité de recherché 12SP18, A Mami Pneumology Hospital, Ariana, Faculty of Mathematical, Physical and Natural Sciences of Tunis, University of Tunis El Manar, Tunis, Tunisia. 2. Emerging Bacterial Pathogens Unit, Division of Immunology, Transplantation and Infectious Diseases, Istituto di Ricovero e Cura a Carattere Scientifico San Raffaele Scientific Institute, Milan, Italy. 3. National Reference Laboratory for Mycobacteria, Unité de recherché 12SP18, A Mami Pneumology Hospital, Ariana. 4. National Reference Laboratory for Mycobacteria, Unité de recherché 12SP18, A Mami Pneumology Hospital, Ariana, Faculty of Pharmacy, University of Monastir, Monastir, Tunisia.
Abstract
SETTING: Phenotypic tests used to detect pyrazinamide (PZA) resistance are slow and have a high rate of false resistance. OBJECTIVE: To evaluate the accuracy of pncA sequencing for the detection of PZA resistance in Mycobacterium tuberculosis strains isolated in Tunisia. DESIGN: A total of 82 isolates, 41 resistant and 41 susceptible to PZA on BACTEC™ MGIT™ 960, were sequenced for pncA. Whole genome sequencing was performed for strains that were phenotypically resistant and had wild-type pncA in addition to MGIT retesting with a modified protocol. RESULTS: Twenty-three strains resistant to PZA with negative pyrazinamidase (PZase) activity harboured a mutation in the promoter or coding region of pncA. However, 18 strains resistant to PZA did not present any mutation. Repeat MGIT 960 showed that 16 of 18 M. tuberculosis isolates were falsely resistant to PZA. Compared with MGIT, PZase activity assay and pncA sequencing both presented a sensitivity of 92.0% (95%CI 73.9-99.0) and a specificity of respectively 96.5% (positive predictive value [PPV] 92.0%, negative predictive value [NPV] 96.5%) and 100.0% (PPV 100.0%, NPV 96.6%). CONCLUSION: The standard MGIT assay showed a high rate of false resistance to PZA, and the PZase activity assay is slow. pncA sequencing could therefore represent a rapid, accurate, alternative test to detect PZA resistance.
SETTING: Phenotypic tests used to detect pyrazinamide (PZA) resistance are slow and have a high rate of false resistance. OBJECTIVE: To evaluate the accuracy of pncA sequencing for the detection of PZA resistance in Mycobacterium tuberculosis strains isolated in Tunisia. DESIGN: A total of 82 isolates, 41 resistant and 41 susceptible to PZA on BACTEC™ MGIT™ 960, were sequenced for pncA. Whole genome sequencing was performed for strains that were phenotypically resistant and had wild-type pncA in addition to MGIT retesting with a modified protocol. RESULTS: Twenty-three strains resistant to PZA with negative pyrazinamidase (PZase) activity harboured a mutation in the promoter or coding region of pncA. However, 18 strains resistant to PZA did not present any mutation. Repeat MGIT 960 showed that 16 of 18 M. tuberculosis isolates were falsely resistant to PZA. Compared with MGIT, PZase activity assay and pncA sequencing both presented a sensitivity of 92.0% (95%CI 73.9-99.0) and a specificity of respectively 96.5% (positive predictive value [PPV] 92.0%, negative predictive value [NPV] 96.5%) and 100.0% (PPV 100.0%, NPV 96.6%). CONCLUSION: The standard MGIT assay showed a high rate of false resistance to PZA, and the PZase activity assay is slow. pncA sequencing could therefore represent a rapid, accurate, alternative test to detect PZA resistance.
Authors: Eleanor S Click; Ekaterina V Kurbatova; Heather Alexander; Tracy L Dalton; Michael P Chen; James E Posey; Julia Ershova; J Peter Cegielski Journal: J Infect Dis Date: 2020-06-11 Impact factor: 5.226
Authors: M J Nasiri; F Fardsanei; M Arshadi; B Deihim; Farima Khalili; M Dadashi; M Goudarzi; M Mirsaeidi Journal: New Microbes New Infect Date: 2021-05-05