Novel approaches for the diagnosis of drug-resistance, treatment response, and infectiousness in patients with tuberculosis (the eDIToR study – Diagnosis Infectiousness and Treatment Response)
Date
2020-03
Authors
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Journal ISSN
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Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Drug-resistance tuberculosis (DR-TB) is a major challenge facing TB control. Limiting personto-person transmission is key. This can be done by reducing time to drug susceptibility
diagnosis and effective treatment initiation, which reduces infectiousness. Furthermore, DRTB patients have suboptimal outcomes even on effective treatment and we have few methods
for monitoring treatment response. If patients are not responding to treatment, better methods
are required to measure infectiousness so that transmission may be limited.
First, to alleviate the under-diagnosis of drug-resistance stemming from additional sputa not
submitted for drug susceptibility testing (DST) and infrastructural barriers, we showed that
cartridge extract (CE) from used TB-positive Xpert MTB/RIF (Xpert) tests is directly usable
for MTBDRsl (a second-line molecular DST). Furthermore, we showed that CE was useful for
spoligotyping for molecular epidemiology.
Second, we showed that this CE approach is feasible on Xpert MTB/RIF Ultra (Ultra), which
is Xpert’s successor. We also evaluated the risk of rpoB amplicon escape during the extraction
and the usefulness of material in other cartridge chambers for different molecular tests. In short, cross-contamination was possible but appears extremely unlikely. Only the diamond cartridge
compartment contains useful material.
Third, MTBDRsl itself has limitations. For example, it only measures susceptibility to two drug
classes. We assessed the feasibility of ultra-deep sequencing (single molecule overlapping
reads, SMOR) on CE. SMOR had more actionable results (useful for clinical decision making)
on Xpert CE than Ultra CE, and detected micro-heteroresistance missed by conventional DST.
Next, to evaluate the utility of new tools for treatment response, we leveraged a MDR-TB drug
trial (NeXT, Clinicaltrials.gov #NCT02454205) to collect serial sputa. We assessed if sputa
contained differentially culturable tubercle bacilli (DCTB) with a dormancy-associated.
Description
Thesis (PhD)--Stellenbosch University, 2020.
Keywords
Tuberculosis, Drug resistance -- Tuberculosis, Infectious diseases, Treatment monitoring, Clinical research, Multidrug resistance -- Diagnosis