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. 2017 Jun 19;7(1):3790.
doi: 10.1038/s41598-017-03452-y.

A Multinational Analysis of Mutations and Heterogeneity in PZase, RpsA, and PanD Associated with Pyrazinamide Resistance in M/XDR Mycobacterium tuberculosis

S M Ramirez-Busby  1 , T C Rodwell  2 , L Fink  1 , D Catanzaro  3 , R L Jackson  2 , M Pettigrove  2 , A Catanzaro  2 , F Valafar  4
Affiliations

A Multinational Analysis of Mutations and Heterogeneity in PZase, RpsA, and PanD Associated with Pyrazinamide Resistance in M/XDR Mycobacterium tuberculosis

S M Ramirez-Busby et al. Sci Rep. .

Abstract

Pyrazinamide (PZA) is an important first-line drug in all existing and new tuberculosis (TB) treatment regimens. PZA-resistance in M. tuberculosis is increasing, especially among M/XDR cases. Noted issues with PZA Drug Susceptibility Testing (DST) have driven the search for alternative tests. This study provides a comprehensive assessment of PZA molecular diagnostics in M/XDR TB cases. A set of 296, mostly XDR, clinical M. tuberculosis isolates from four countries were subjected to DST for eight drugs, confirmatory Wayne's assay, and whole-genome sequencing. Three genes implicated in PZA resistance, pncA, rpsA, and panD were investigated. Assuming all non-synonymous mutations cause resistance, we report 90% sensitivity and 65% specificity for a pncA-based molecular test. The addition of rpsA and panD potentially provides 2% increase in sensitivity. Molecular heterogeneity in pncA was associated with resistance and should be evaluated as a diagnostic tool. Mutations near the N-terminus and C-terminus of PZase were associated with East-Asian and Euro-American lineages, respectively. Finally, Euro-American isolates are most likely to have a wild-type PZase and escape molecular detection. Overall, the 8-10% resistance without markers may point to alternative mechanisms of resistance. Confirmatory mutagenesis may improve the disconcertingly low specificity but reduce sensitivity since not all mutations may cause resistance.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Distribution of pncA mutations in (a) PZAR and (b) PZAS clinical M. tuberculosis isolates. Frequencies labeled as “Heterogeneous” represent calls that had sufficient support for both a variant and the reference, indicative of mixed populations. “Monoclonal” frequencies represent calls that were clearly supportive of a variant. The frequencies presented here are the totals over all the different mutations observed at each codon.
See this image and copyright information in PMC

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