Browsing by Author "Alberts, Rencia"

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    Resistance to new tuberculosis drugs
    (Stellenbosch : Stellenbosch University,, 2024-03) Alberts, Rencia; Theron, Grant; Derendinger, Brigitta; Venter, Rouxjeane; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Molecular Biology and Human Genetics.
    ENGLISH ABSTRACT: Introduction: Tuberculosis (TB) is a leading worldwide cause of death, further exacerbated by drug-resistant (DR)-TB. Therefore, new TB drugs are urgently needed. Bedaquiline (BDQ) is the first new TB drug in 40 years and is used for DR-TB treatment. BDQ resistance has, however, already been identified and, at the time of the study, routine phenotypic drug susceptibility testing (pDST) was not done on people initiating BDQ. Additionally, it's important to implement routine DR monitoring for BDQ and other companion drugs. Furthermore, little is known about phenotypic changes over time and whether increases in minimum inhibitory concentrations (MICs) could predict the later DR emergence. Additionally, we aimed to look at the performance of a molecular diagnostic assay for all 13 TB drugs (FLeXT) and determine its sensitivity and specificity. Methods: We determined how MICs from people who started on BDQ with sustained culture positivity changed over time from baseline (BL: closest isolate to BDQ treatment start) to follow up (FU: closest isolate to four-month sustained culture positivity) using a MIC microtitre plate from CRyPTIC. The plate included all 13 TB drugs, including new and repurposed drugs. Additionally, intercedent isolates were also tested using CRyPTIC to look at the change in MIC over time. Furthermore, we sequenced 720 sputa isolates using a manual extraction kit and the GenoXtract kit needed for the FLeXT machine. Results: BDQ MICs increased (p=0.0002) between BL [Median IQR: 0.008 (0.004-0.015)] and FU [Median IQR: 0.030 (0.015-0.019)]. The BDQ isolates had 14/17 (82.5%) isolates showing an increase in MIC over time. Isolates who had sustained culture positivity over time while on BDQ also showed larger increases in BDQ MIC over time compared to the BDQ susceptible https://scholar.sun.ac.za 6 group. Furthermore, for those isolates that indicated BDQ resistance at FU, companion drugs also indicated a higher level of variants and greater increases in CRyPTIC MIC over time. The largest increases in variants and CRyPTIC MICs were found for ethambutol (EMB), the fluoroquinolones (FQs), and ethionamide (ETH). No variants were found for the other new and repurposed drugs: clofazimine (CFZ, delamanid (DLM), or linezolid (LZD) at either timepoint, for both resistance groups. Lastly, FLeXT had a sensitivity of 87% using the manual extraction method (Fluorolyse) and aN 86% specificity for the automated extraction method (FleXT). Conclusion: This highlights the importance of doing routine testing for new drugs such as BDQ as well as companion drugs in people with DR-TB. Our results indicate that there is often a slow increase in CRyPTIC MIC that would lead to resistance over time, and this should be considered in patients with sustained culture positivity). Therefore, it is important to do resistance detection for TB drugs before initiating anyone on a regimen for the treatment to be effective. Furthermore, we proved that the FLeXT GenoXtract has great performance in the detection of DR for second-line TB drugs and serves as a much more efficient way of detecting second-line drug resistance. Molecular assays like this will improve the diagnosis pipeline and help clinicians form individualised treatment plans.