scholarly journals Overcoming the Challenges of Pyrazinamide Susceptibility Testing in Clinical Mycobacterium tuberculosis isolates

2021 ◽  
Author(s):  
Simone Mok ◽  
Emma Roycroft ◽  
Peter R Flanagan ◽  
Lorraine Montgomery ◽  
Emanuele Borroni ◽  
...  
Keyword(s):  
Sanger Sequencing ◽  
Susceptibility Testing ◽  
Critical Concentration ◽  
Drug Susceptibility ◽  
Rapid Identification ◽  
Drug Susceptibility Testing ◽  
Whole Genome ◽  
Testing Methods ◽  
First Line ◽  
Phenotypic Susceptibility

Pyrazinamide (PZA) is one of the first-line agents used for the treatment of tuberculosis. However, current phenotypic PZA susceptibility testing in the BACTEC MGIT 960 system is unreliable and false resistance is well documented. Rapid identification of resistance-associated mutations can confirm the phenotypic result. This study aimed to investigate the use of genotypic methods in combination with phenotypic susceptibility testing for confirmation of PZA resistant M. tuberculosis isolates. Sanger sequencing and/or whole genome sequencing were performed to detect mutations in pncA, rpsA, panD and clpC1. Isolates were screened for heteroresistance, and PZA susceptibility testing was performed in the BACTEC MGIT 960 system using a reduced inoculum to investigate false resistance. Overall, 40 phenotypically PZA resistant isolates were identified. Of these, PZA resistance was confirmed in 22/40 (55%) isolates by detecting mutations in pncA, rpsA and panD genes. 16/40 (40%) isolates were found to be susceptible using the reduced inoculum method (i.e. false resistance). No mutations were detected in two PZA resistant isolates. False resistance was observed in isolates with MICs close to the critical concentration. In particular, EAI strains (lineage 1) appeared to have an elevated MIC that is close to the critical concentration. While this study illustrates the complexity and challenges associated with PZA susceptibility testing of M. tuberculosis, we conclude that a combination of genotypic and phenotypic drug susceptibility testing methods is required for accurate detection of PZA resistance.

scholarly journals How To Optimally Combine Genotypic and Phenotypic Drug Susceptibility Testing Methods for Pyrazinamide

2020 ◽  
Vol 64 (9) ◽  
Author(s):  
Claudio U. Köser ◽  
Daniela M. Cirillo ◽  
Paolo Miotto
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Current Practice ◽  
Susceptibility Testing ◽  
Critical Concentration ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Resistance Mutations ◽  
Testing Methods ◽  
Content Type

ABSTRACT False-susceptible phenotypic drug-susceptibility testing (DST) results for pyrazinamide due to mutations with MICs close to the critical concentration (CC) confound the classification of pncA resistance mutations, leading to an underestimate of the specificity of genotypic DST. This could be minimized by basing treatment decisions on well-understood mutations and by adopting an area of technical uncertainty for phenotypic DST rather than only testing the CC, as is current practice for the Mycobacterium tuberculosis complex.

scholarly journals Fluoroquinolone susceptibility in first-line drug-susceptible M. tuberculosis isolates in Lima, Peru

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Alvaro Schwalb ◽  
Rodrigo Cachay ◽  
Ericka Meza ◽  
Tatiana Cáceres ◽  
Amondrea Blackman ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Critical Concentration ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
First Line ◽  
Viable Option ◽  
Time Points ◽  
Line Drug

Abstract Objective To determine at two distinct time points the prevalence of resistance to ofloxacin (OFX), the representative class drug of fluoroquinolones (FQs), in M. tuberculosis isolates susceptible to first-line drugs. Results There were 279 M. tuberculosis isolates from the two cohorts (2004–2005: 238 isolates; 2017: 41 isolates) that underwent OFX drug-susceptibility testing (critical concentration: 2 µg/ml). Of 238 isolates in Cohort 1, no resistance to OFX was detected (95% CI 0–0.016); likewise, in Cohort 2, no resistance to OFX was detected in 41 isolates (95% CI 0–0.086). Our findings suggest that FQ use remains a viable option for the treatment of first-line drug-susceptible TB in Peru.

scholarly journals Susceptibility Testing of Extensively Drug-Resistant and Pre-Extensively Drug-Resistant Mycobacterium tuberculosis against Levofloxacin, Linezolid, and Amoxicillin-Clavulanate

2013 ◽  
Vol 57 (6) ◽  
pp. 2522-2525 ◽  
Author(s):  
Imran Ahmed ◽  
Kauser Jabeen ◽  
Raunaq Inayat ◽  
Rumina Hasan
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Susceptibility Testing ◽  
Critical Concentration ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Fluoroquinolone Resistance ◽  
Drug Resistant ◽  
Content Type ◽  
Extensively Drug Resistant ◽  
Amoxicillin Clavulanate

ABSTRACTPakistan is a high-burden country for tuberculosis (TB). The emergence and increasing incidence of extensively drug-resistant (XDR) TB has been reported in Pakistan. Similarly, the prevalence of multidrug-resistant TB infections with fluoroquinolone resistance (pre-XDR) is also increasing. To treat these infections, local drug susceptibility patterns of alternate antituberculosis agents, including levofloxacin (LVX), linezolid (LZD), and amoxicillin-clavulanate (AMC), is urgently needed. The aim of this study was to determine the susceptibility frequencies of drug-resistant (DR)Mycobacterium tuberculosisagainst LVX, LZD, and AMC. All susceptibilities were determined on Middlebrook 7H10 agar. A critical concentration was used for LVX (1 μg/ml), whereas MICs were determined for LZD and AMC.M. tuberculosisH37Rv was used as a control strain. A total of 102M. tuberculosisisolates (XDR,n= 59; pre-XDR,n= 43) were tested. Resistance to LVX was observed in 91.2% (93/102). Using an MIC value of 0.5 μg/ml as a cutoff, resistance to LZD (MIC ≥ 1 μg/ml) was noted in 5.9% (6/102). Although the sensitivity breakpoints are not established for AMC, the MIC values were high (>16 μg/ml) in 97.1% (99/102). Our results demonstrate that LZD may be effective for the treatment of XDR and pre-XDR cases from Pakistan. High resistance rates against LVX in our study suggest the use of this drug with caution for DR-TB cases from this area. Drug susceptibility testing against LVX and AMC may be helpful in complicated and difficult-to-manage cases.

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