Immunological detection of pyrazine-2-carboxylic acid for the detection of pyrazinamide resistance in Mycobacterium tuberculosis

A simplified pyrazinamidase test for Mycobacterium tuberculosis pyrazinamide antimicrobial susceptibility testing

Pyrazinamide (PZA) is an important first-line drug for tuberculosis (TB) treatment by eradicating the persisting Mycobacterium tuberculosis complex (MTBC). Due to cost and technical challenges, end TB strategies are hampered by the lack of a simple and reliable culture-based PZA antimicrobial susceptibility testing (AST) for routine use. We initially developed a simplified chromogenic pyrazinamidase (PZase) test in the TB reference laboratory using a training set MTBC isolates with various drug-resistant profiles, and validated its performance using consecutive BACTEC MGIT 960 (MGIT)-culture-positive culture in 10 clinical laboratories. The pncA gene Sanger sequencing results were used as the reference, and compared to the MGIT-PZA AST. Differential diagnosis of Mycobacterium bovis was conducted using patented in-house real-time PCR. Of the 106 training isolates, the PZase test and MGIT-PZA AST showed 100.0% and 99.1% concordance as compared to Sanger sequencing, respectively. We found 32.1% (34/106) isolates harbored pncA mutations, including one isolate with silent mutation S65S. For validation, 1,793 clinical isolates were tested including 150 duplicate isolates from specimens of the same cases and 16 isolates with uncharacterized drug resistance (UDR)-associated mutations. Excluding duplicated and UDR isolates, we identified 2.6% (43/1,627) PZA-resistant isolates, including 1.3% (21/1,627) M. bovis isolates. The kappa values were 0.851-1.000. In addition, the accuracy of the PZase test conducted by 10 laboratories was 98.5%-100.0%. Our simplified PZase test demonstrated high concordance with Sanger sequencing and MGIT-PZA AST. Integrating the PZase test into routine first-line AST is effortless and represents an improvement in laboratory services for ending TB.

IMPORTANCE

We developed and validated a simple pyrazinamidase (PZase) test for pyrazinamide (PZA) antimicrobial susceptibility testing (AST). Our results demonstrated that the PZase test had high agreement with the pncA gene sequencing and MGIT-PZA AST. Integrating PZase test into routine AST is effortless and represents an improvement in laboratory services for ending TB.

Prussian blue (PB) modified gold nanoparticles as a SERS-based sensing platform for capturing and detection of pyrazinoic acid (POA)

Pyrazinoic acid (POA) is a metabolite of the anti-tuberculosis drug pyrazinamide (PZA), and its detection can be used to assess the resistance of Mycobacterium tuberculosis in cultures, as only sensitive strains of the bacteria can metabolize PZA into POA. Prussian blue is a well-known metal-organic framework compound widely used in various sensing platforms such as electrochemical, photochemical, and magnetic sensors. In this study, we present a novel sensing platform based on Prussian blue-modified gold nanoparticles (AuNPs) designed to enhance the affinity of POA towards the sensing surface and to capture POA molecules from aqueous solutions. This SERS-based method allows for the selective enrichment of POA, which can be detected in both pure aqueous solution and in the presence of its pro-drug PZA. The limit of detection (LOD) for POA was estimated to be 1.08 μM in pure aqueous solution and 0.18 mM in the presence of PZA. Furthermore, the precision of the SERS method was verified by the relative standard deviation (RSD) of 3.34-12.02% for three parallel samples using different matrices, i.e. aqueous solution, spiked river water and spiked simulated saliva. The recoveries of the samples ranged from 92.65 to 118.51%. These all demonstrate the potential application of the proposed detection scheme in medical research.

Correction: Immunological detection of pyrazine-2-carboxylic acid for the detection of pyrazinamide resistance in Mycobacterium tuberculosis

[This corrects the article DOI: 10.1371/journal.pone.0241600.].