3 research outputs found
Undetected isoniazid mono resistance in rural Eastern Cape Province - A risk for the emergence of multidrug-resistant TB
No full textThesis (MSc)--Stellenbosch University, 2021.ENGLISH ABSTRACT: The emergence of drug-resistant tuberculosis (TB) remains a major challenge in South
Africa, particularly the Eastern Cape, being one of the most severely affected provinces in the
country. Due to resource limitations, many isoniazid (INH) mono-resistant TB cases remain
undiagnosed, as TB control programmes generally focus on rifampicin-resistant strains.
Rifampicin resistance, which is a marker of multidrug-resistant (MDR) TB, is more difficult
to treat than INH mono-resistant (IMR) TB, often resulting in high morbidity and mortality.
The effectiveness of INH, an important first-line anti-TB drug, has been compromised by
resistance, which arises through spontaneous mutations in the genome of Mycobacterium
tuberculosis (M. tuberculosis). Occurrence of these mutations is often missed by the current
diagnostic algorithm, which fails to detect IMR-TB cases at diagnosis, hence threatening the
efficacy of TB treatment. Consequently, these patients are likely to be treated with a
weakened regimen, which may increase the risk of treatment failure or relapse. Previous
studies have reported IMR as the source for the emergence of MDR-TB.
This study aimed to provide the first in-depth analysis of the molecular epidemiology of
IMR-TB in the Eastern Cape. Clinical isolates from patients with rifampicin-susceptible TB
were obtained via the National Health Laboratory Services (NHLS) in Port Elizabeth and
analysed by using a series of microbiological and molecular techniques. These tests were
done to identify IMR-TB cases, describe the molecular mechanisms of INH resistance,
identify cases of acquisition of IMR and MDR, as well as to describe risk factors associated
with IMR at diagnosis (baseline). We also used spoligotyping to classify isolates into their
respective lineages and strain families.
Phenotypic INH drug susceptibility testing on solid media identified 107 (13.9%) cases of
IMR among the cohort of 993 TB cases enrolled, which was nearly double the estimated
national average. No association between patient demographic or clinical parameters was
identified. This may be due to the inaccuracies of the electronic TB database. Genetic drug
susceptibility testing only identified causal mutations in 25 baseline isolates, while 4 baseline
isolates showed evidence of heteroresistance, possibly masking the detection of underlying
INH-resistant populations. This was confirmed in a small sub-analysis using a highly
sensitive targeted deep sequencing approach. Subsequent analysis of serial isolates showed
acquisition of IMR in 9 cases, as well as loss of IMR in 12 cases. Repeat analysis identified heteroresistance as the possible cause of the observed flip flopping of the IMR phenotype.
Spoligotyping failed to identify reinfection as a major mechanism causing the flip flopping
IMR phenotype. IMR was associated with the Atypical Beijing genotype (p < 0.0001).
This study highlights the need to change TB policy through: (1) understanding the local
epidemiology of IMR to identify potential risk factors for targeted interventions and to
strengthen current first-line regimens for the continuation phase of TB treatment, (2)
improving surveillance studies in neglected rural areas by monitoring IMR to inform policy,
(3) developing new rapid molecular technologies to ensure early identification of IMR-TB
cases and close monitoring of patients following appropriate treatment and care. These
strategies will be essential to contain the spread of IMR-TB, improve outcomes and prevent
progression of disease to more severe forms of drug resistance often culminating in death.AFRIKAANSE OPSOMMING: Die opkoms van middelweerstandige tuberkulose (TB) bly 'n groot uitdaging in Suid-Afrika,
veral die Oos-Kaap, as een van die provinsies in die land wat die ergste geraak word. As
gevolg van hulpbronbeperkte kapasiteit, bly baie isoniasid (INH) mono-weerstandige TB
gevalle nie gediagnoseer nie, aangesien TB-beheerprogramme oor die algemeen fokus op
rifampisin-weerstandige stamme. Rifampisin weerstand is 'n merker van multimiddel weerstandige (MDR) TB, wat moeiliker is om te behandel as INH mono-weerstandige (IMR)
TB, wat dikwels lei tot hoë morbiditeit en mortaliteit.
Die effektiwiteit van INH, 'n belangrike eersterangse middel teen TB, word verminder deur
weerstand wat ontstaan deur spontane mutasies in die genoom Mycobacterium tuberculosis
(M. tuberculosis). Die voorkoms van hierdie mutasies word dikwels gemis deur die huidige
diagnostiese algoritme, wat nie IMR-TB-gevalle kan opspoor tydens diagnose nie. Gevolglik
word die doeltreffendheid van TB-behandeling bedreig, aangesien hierdie pasiënte meer
geneig is om met 'n verswakte behandeling behandel te word, wat die risiko van versuim of
terugval kan verhoog. Vorige studies het IMR as die bron vir die opkoms van MDR-TB
gerapporteer.
Hierdie studie het ten doel gehad om die eerste diepgaande analise van die molekulêre
epidemiologie van IMR-TB in die Oos-Kaap te bied. Kliniese isolate van pasiënte met
rifampisin-vatbare TB is verkry deur die National Health Laboratory Services (NHLS) in Port
Elizabeth en geanaliseer deur gebruik te maak van 'n reeks mikrobiologiese en molekulêre
tegnieke. Hierdie toetse is gedoen om IMR-TB-gevalle te identifiseer, die molekulêre
meganismes van INH-weerstand te beskryf, gevalle van verkryging van IMR en MDR te
identifiseer, asook om risikofaktore wat verband hou met IMR tydens diagnose (basislyn) te
beskryf. Ons het ook spoligotipering gebruik om isolate in hul onderskeie geslagte en
stamfamilies te klassifiseer.
Fenotipiese toetsing vir vatbaarheid vir INH-geneesmiddels op vaste media het 107 (13,9%)
gevalle van IMR geïdentifiseer onder die groep 993 TB-gevalle wat ingeskryf is, wat byna
dubbel die geskatte nasionale gemiddelde was. Geen verband tussen pasiënte se demografiese
of kliniese parameters is geïdentifiseer nie. Dit kan te wyte wees aan die onakkuraathede van
die elektroniese databasis. Die toetsing van vatbaarheid vir genetiese geneesmiddels het slegs
oorsaaklike mutasies in 25 basislyn-isolate geïdentifiseer, terwyl vier basislyn-isolate bewyse van heteroresistensie getoon het, wat moontlik die opsporing van onderliggende INH weerstandige populasies kon wegsteek. Dit is bevestig in 'n klein sub-analise deur gebruik te
maak van 'n baie sensitiewe, gerigte diepvolgorde-benadering. Daaropvolgende ontleding van
reeksisolate het die verkryging van IMR in 9 gevalle getoon, asook verlies aan IMR in 12
gevalle. Heranalise het heteroresistensie geïdentifiseer as die moontlike oorsaak van die
waargenome “flip-flopping” van die IMR-fenotipe. Spoligotipering kon nie herinfeksie
identifiseer as 'n belangrike meganisme wat die IMR-fenotipe omkeer. IMR word geassosieer
met die Atipiese Beijing-genotipe (p <0.0001).
Hierdie studie beklemtoon die behoefte om TB-beleid te verander deur: (1) die plaaslike
epidemiologie van IMR te verstaan om potensiële risikofaktore vir geteikende intervensies te
identifiseer en die huidige eerste-lyn-regimes vir die voortsettingsfase van TB-behandeling te
versterk, (2) verbetering van toesigstudies by verwaarloosde landelike gebiede deur IMR te
monitor om beleid in te lig, (3) die ontwikkeling van nuwe vinnige molekulêre tegnologieë
om vroeë identifikasie van IMR-TB-gevalle te verseker en noukeurige monitering van
pasiënte na toepaslike behandeling en sorg. Hierdie strategieë is noodsaaklik om die
verspreiding van IMR te beperk, die uitkomste te verbeter en die progressie van siektes na
meer ernstige vorme van middelweerstandigheid te voorkom, wat dikwels op die dood
uitloop.Master
Integrating molecular and radiological screening tools during community-based active case-finding for tuberculosis and COVID-19 in southern Africa
No full textObjectives: To evaluate diagnostic yield and feasibility of integrating testing for TB and COVID-19 using molecular and radiological screening tools during community-based active case-finding (ACF). Methods: Community-based participants with presumed TB and/or COVID-19 were recruited using a mobile clinic. Participants underwent simultaneous point-of-care (POC) testing for TB (sputum; Xpert Ultra) and COVID-19 (nasopharyngeal swabs; Xpert SARS-CoV-2). Sputum culture and SARS-CoV-2 RT-PCR served as reference standards. Participants underwent ultra-portable POC chest radiography with computer-aided detection (CAD). TB infectiousness was evaluated using smear microscopy, cough aerosol sampling studies (CASS), and chest radiographic cavity detection. Feasibility of POC testing was evaluated via user-appraisals. Results: Six hundred and one participants were enrolled, with 144/601 (24.0%) reporting symptoms suggestive of TB and/or COVID-19. 16/144 (11.1%) participants tested positive for TB, while 10/144 (6.9%) tested positive for COVID-19 (2/144 [1.4%] had concurrent TB/COVID-19). Seven (7/16 [43.8%]) individuals with TB were probably infectious. Test-specific sensitivity and specificity (95% CI) were: Xpert Ultra 75.0% (42.8-94.5) and 96.9% (92.4-99.2); Xpert SARS-CoV-2 66.7% (22.3-95.7) and 97.1% (92.7-99.2). Area under the curve (AUC) for CAD4TB was 0.90 (0.82-0.97). User appraisals indicated POC Xpert to have ‘good’ user-friendliness. Conclusions: Integrating TB/COVID-19 screening during community-based ACF using POC molecular and radiological tools is feasible, has a high diagnostic yield, and can identity probably infectious persons
