Genotype-Phenotype Characterization of Serial Mycobacterium tuberculosis Isolates in Bedaquiline-Resistant Tuberculosis.

BACKGROUND: Emerging resistance to bedaquiline (BDQ) threatens to undermine advances in the treatment of drug-resistant tuberculosis (DRTB). Characterizing serial Mycobacterium tuberculosis (Mtb) isolates collected during BDQ-based treatment can provide insights into the etiologies of BDQ resistance in this important group of DRTB patients. METHODS: We measured mycobacteria growth indicator tube (MGIT)-based BDQ minimum inhibitory concentrations (MICs) of Mtb isolates collected from 195 individuals with no prior BDQ exposure who were receiving BDQ-based treatment for DRTB. We conducted whole-genome sequencing on serial Mtb isolates from all participants who had any isolate with a BDQ MIC >1 collected before or after starting treatment (95 total Mtb isolates from 24 participants). RESULTS: Sixteen of 24 participants had BDQ-resistant TB (MGIT MIC ≥4 µg/mL) and 8 had BDQ-intermediate infections (MGIT MIC = 2 µg/mL). Participants with pre-existing resistance outnumbered those with resistance acquired during treatment, and 8 of 24 participants had polyclonal infections. BDQ resistance was observed across multiple Mtb strain types and involved a diverse catalog of mmpR5 (Rv0678) mutations, but no mutations in atpE or pepQ. Nine pairs of participants shared genetically similar isolates separated by <5 single nucleotide polymorphisms, concerning for potential transmitted BDQ resistance. CONCLUSIONS: BDQ-resistant TB can arise via multiple, overlapping processes, including transmission of strains with pre-existing resistance. Capturing the within-host diversity of these infections could potentially improve clinical diagnosis, population-level surveillance, and molecular diagnostic test development.

Tubercular Uveitis in Uveitis Cases in a High TB and HIV Setting: A Prospective Cohort Study.

Purpose: The diagnosis of tubercular uveitis (TBU) is difficult. The lack of a diagnostic gold standard has contributed to challenges in determining the true prevalence and clinical predictors of TBU. We aimed to determine the proportion of TBU cases in adults with uveitis and to examine clinical features associated with TBU. Methods: A prospective cohort study of adult uveitis cases after exclusion of other specific etiologies. The diagnosis of TBU was based on a composite reference of: any clinical signs of uveitis; exclusion of other causes of uveitis; and positive QuantiFERON-Gold test, tuberculin skin test, and/or ocular TB polymerase chain reaction. Results: Of 79 cases analyzed, 49 (62%) had TBU. Female sex (P = 0.001) and chronic uveitis (P = 0.006) cases were more common in the TBU group than the non-TBU group whereas diffuse choroiditis (P = 0.010) and HIV-positive (P = 0.001) cases were less common. Choroidal granulomas (P = 0.176) and serpiginous-like choroiditis (P = 0.292) were more common in TBU group, albeit not significantly. On univariate analysis, female sex (odds ratio, 5.1; P = 0.002), negative HIV status (odds ratio, 0.2; P = 0.001), and chronic uveitis (odds ratio, 4.1; P = 0.008) were associated with TBU. A negative HIV test was associated with TBU on multivariate analysis (P = 0.049). Conclusions: A high proportion of cases had TBU. Our study did not significantly confirm some of the clinical features associated with TBU reported in other studies. Translational Relevance: Our study highlights the difficulties in determining the proportion and clinical predictors of TBU, especially in the absence of a gold standard diagnostic test.

Assessment of epidemiological and genetic characteristics and clinical outcomes of resistance to bedaquiline in patients treated for rifampicin-resistant tuberculosis: a cross-sectional and longitudinal study.

BACKGROUND: Bedaquiline improves outcomes of patients with rifampicin-resistant and multidrug-resistant (MDR) tuberculosis; however, emerging resistance threatens this success. We did a cross-sectional and longitudinal analysis evaluating the epidemiology, genetic basis, and treatment outcomes associated with bedaquiline resistance, using data from South Africa (2015-19). METHODS: Patients with drug-resistant tuberculosis starting bedaquiline-based treatment had surveillance samples submitted at baseline, month 2, and month 6, along with demographic information. Culture-positive baseline and post-baseline isolates had phenotypic resistance determined. Eligible patients were aged 12 years or older with a positive culture sample at baseline or, if the sample was invalid or negative, a sample within 30 days of the baseline sample submitted for bedaquiline drug susceptibility testing. For the longitudinal study, the first surveillance sample had to be phenotypically susceptible to bedaquiline for inclusion. Whole-genome sequencing was done on bedaquiline-resistant isolates and a subset of bedaquiline-susceptible isolates. The National Institute for Communicable Diseases tuberculosis reference laboratory, and national tuberculosis surveillance databases were matched to the Electronic Drug-Resistant Tuberculosis Register. We assessed baseline resistance prevalence, mutations, transmission, cumulative resistance incidence, and odds ratios (ORs) associating risk factors for resistance with patient outcomes. FINDINGS: Between Jan 1, 2015, and July 31, 2019, 8041 patients had surveillance samples submitted, of whom 2023 were included in the cross-sectional analysis and 695 in the longitudinal analysis. Baseline bedaquiline resistance prevalence was 3·8% (76 of 2023 patients; 95% CI 2·9-4·6), and it was associated with previous exposure to bedaquiline or clofazimine (OR 7·1, 95% CI 2·3-21·9) and with rifampicin-resistant or MDR tuberculosis with additional resistance to either fluoroquinolones or injectable drugs (pre-extensively-drug resistant [XDR] tuberculosis: 4·2, 1·7-10·5) or to both (XDR tuberculosis: 4·8, 2·0-11·7). Rv0678 mutations were the sole genetic basis of phenotypic resistance. Baseline resistance could be attributed to previous bedaquiline or clofazimine exposure in four (5·3%) of 76 patients and to primary transmission in six (7·9%). Odds of successful treatment outcomes were lower in patients with baseline bedaquiline resistance (0·5, 0·3-1). Resistance during treatment developed in 16 (2·3%) of 695 patients, at a median of 90 days (IQR 62-195), with 12 of these 16 having pre-XDR or XDR. INTERPRETATION: Bedaquiline resistance was associated with poorer treatment outcomes. Rapid assessment of bedaquiline resistance, especially when patients were previously exposed to bedaquiline or clofazimine, should be prioritised at baseline or if patients remain culture-positive after 2 months of treatment. Preventing resistance by use of novel combination therapies, current treatment optimisation, and patient support is essential. FUNDING: National Institute for Communicable Diseases of South Africa.

Treatment Outcome of Tubercular Uveitis in a High TB and HIV Setting: A Prospective Cohort Study.

PURPOSE: To determine the time to resolution of inflammation in tubercular uveitis (TBU) cases on standard anti-tubercular treatment. Sub-analysis of time to resolution according to HIV status was also performed. PATIENTS AND METHODS: A prospective cohort study of presumed idiopathic uveitis cases >18 years underwent the tuberculin skin test, QuantiFERON-TB Gold test, and ocular tuberculosis (TB) polymerase chain reaction test. Adult TBU cases were treated with standard anti-tubercular therapy (and corticosteroids) for 9 months. Cases were followed-up for resolution of inflammation at 1.5, 3, 6, 9, 12 and 15 months post-diagnosis. Outcome measure was resolution of inflammation on ≤10 mg oral prednisone per day. RESULTS: Seventy-nine presumed idiopathic uveitis cases were enrolled in the study, 49 (62%) were diagnosed with TBU. The mean (SD) age of TBU cases at diagnosis was 41.8 (13.4) years. Using a multilevel mixed effects model, resolution was achieved at 6 months in the TBU cases (OR = 1.21; 95% CI, 1.03-1.41; P = 0.017). Using generalized estimating equations, resolution was also achieved at 6 months in the TBU cases (OR = 1.21; 95% CI, 1.05-1.39; P = 0.008). The HIV-positive cases (OR = 1.62; 95% CI, 1.13-2.31; P = 0.008) and the HIV-negative cases (OR = 1.25; 95% CI, 1.06-1.48; P = 0.009) achieved resolution at 9 months. CONCLUSION: Resolution of inflammation in TBU cases on anti-tubercular treatment with corticosteroids was achieved at 6 months and maintained throughout the study. Our study suggests a minimum of 6 months treatment is required for significant resolution. Resolution of inflammation in HIV-positive and HIV-negative TBU cases needs to be further explored.

Validation of Bedaquiline Phenotypic Drug Susceptibility Testing Methods and Breakpoints: a Multilaboratory, Multicountry Study.

Drug-resistant tuberculosis persists as a major public health concern. Alongside efficacious treatments, validated and standardized drug susceptibility testing (DST) is required to improve patient care. This multicountry, multilaboratory external quality assessment (EQA) study aimed to validate the sensitivity, specificity, and reproducibility of provisional bedaquiline MIC breakpoints and World Health Organization interim critical concentrations (CCs) for categorizing clinical Mycobacterium tuberculosis isolates as susceptible/resistant to the drug. Three methods were used: Middlebrook 7H11 agar proportion (AP) assay, broth microdilution (BMD) assay, and mycobacterial growth indicator tube (MGIT) assay. Each of the five laboratories tested the 40-isolate (20 unique isolates, duplicated) EQA panel at three time points. The study validated the sensitivity and specificity of a bedaquiline MIC susceptibility breakpoint of 0.12 µg/ml for the BMD method and WHO interim CCs of 1 µg/ml for MGIT and 0.25 µg/ml for the 7H11 AP methods. Categorical agreements between observed and expected results and sensitivities/specificities for correctly identifying an isolate as susceptible/resistant were highest at the 0.25, 0.12, and 1 µg/ml bedaquiline concentrations for the AP method, BMD (frozen or dry plates), and MGIT960, respectively. At these concentrations, the very major error rates for erroneously categorizing an isolate as susceptible when it was resistant were the lowest and within CLSI guidelines. The most highly reproducible bedaquiline DST methods were MGIT960 and BMD using dry plates. These findings validate the use of standardized DST methodologies and interpretative criteria to facilitate routine phenotypic bedaquiline DST and to monitor the emergence of bedaquiline resistance.

Epidemiological cut-offs for Sensititre susceptibility testing of Mycobacterium tuberculosis: interpretive criteria cross validated with whole genome sequencing.

Universal drug susceptibility testing (DST) is an important requirement of the End TB Strategy. The Sensititre broth micro-dilution assay (BMD) tests multiple drugs quantitatively. We defined interpretive criteria for this assay and analysed genotypic-phenotypic relationships. 385 Mycobacterium tuberculosis clinical isolates were processed for BMD and whole genome sequencing. The epidemiological cut-off value 99% (ECV99) amongst genotypically wild type (gWT) strains defined susceptibility. Minimum inhibitory concentration distributions of the resistance-associated variants (RAVs) for each drug were analysed. Susceptibility (µg/mL) criteria were determined as follows: rifampicin (≤0.125), isoniazid (≤0.25), ethambutol (≤2.0), moxifloxacin (≤0.5), levofloxacin (≤1.0), amikacin (≤2.0), kanamycin (≤8.0), capreomycin (≤4.0), clofazimine (≤0.25) and linezolid (≤2.0). Most drugs showed clear separation between gWT and RAV. Isoniazid showed a tri-modal pattern with 14/17 strains at ECV99 harbouring a fabG1 c. -15C > T RAV. Ethambutol RAVs at embB codons 306, 405 and 497 were responsible for resistance and showed differential distributions. Moxifloxacin RAVs (gyrA codon 90) were a dilution or two higher than the ECV99 while gyrB RAVs were uncommon and showed drug specific resistance propensity. Interpretive criteria established were robust facilitating progress towards universal DST and individualised precision medicine. This study demonstrates the value of quantitative DST to accurately interpret mutation data.

Whole genome sequencing for drug resistance determination in Mycobacterium tuberculosis.

South Africa remains challenged with a high tuberculosis burden accompanied by an increase in drug resistant cases. We assessed the use of the Illumina MiSeq, a next-generation sequencing platform for whole genome sequencing, followed by bioinformatic analysis using a commercial software package to determine resistance to selected drugs used for Mycobacterium tuberculosis treatment in our setting. Whole genome sequencing shows potential as a diagnostic platform for the detection of drug resistance in Mycobacterium tuberculosis with the provision of information for several drugs simultaneously.

Whole-Genome Sequence of a Mycobacterium goodii Isolate from a Pediatric Patient in South Africa.

We describe here the draft genome sequence of a Mycobacterium goodii isolate from a pediatric patient in Western Cape, South Africa. To our knowledge, this is the second reported genome of this rapidly growing nontuberculous mycobacterial species.

The Integrity and Yield of Genomic DNA Isolated from Whole Blood Following Long-Term Storage at -30°C.

Long-term storage of whole blood can affect the integrity of DNA if it is not done under optimal conditions. The aim of this study was to determine whether long-term storage (2-19 years) of whole blood samples at -30°C had a negative effect on the quality or quantity of genomic DNA that could be recovered at extraction. Genomic DNA was isolated from 2758 whole blood samples collected in 4 mL EDTA vacutainers from 1997 to 2012. DNA was extracted using the Qiagen® FlexiGene® DNA kit. The average storage duration at -30°C was 12 years. The quality and quantity of the isolated DNA were assessed using spectrophotometry (NanoDrop™), a fluorometric assay for double-stranded DNA (Qubit™), and agarose gel electrophoresis. The mean DNA yield per sample was found to be 114 µg from whole blood volumes that ranged from 0.5 to 4 mL. The mean A260/280 ratio and median A260/280 ratios were both 1.8. No correlation was found between the duration of storage and the total yield or the quality of DNA extracted. These data suggest that high-quality DNA can be extracted from whole blood samples that are stored at -30°C for up to 19 years.

Defining Bedaquiline Susceptibility, Resistance, Cross-Resistance and Associated Genetic Determinants: A Retrospective Cohort Study.

BACKGROUND: Bedaquiline (BDQ) is a novel agent approved for use in combination treatment of multi-drug resistant tuberculosis (MDR-TB). We sought to determine BDQ epidemiological cut-off values (ECVs), define and assess interpretive criteria against putative resistance associated variants (RAVs), microbiological outcomes and cross resistance with clofazimine (CFZ). METHODS: A retrospective cohort study was conducted. Minimal inhibitory concentrations (MIC) to BDQ were determined using 7H9 broth microdilution (BMD) and MGIT960. RAVs were genetically characterised using whole genome sequencing. BDQ ECVs were determined using ECOFFinder and compared with 6-month culture conversion status and CFZ MICs. FINDINGS: A total of 391 isolates were analysed. Susceptible and intermediate categories were determined to have MICs of ≤0.125µg/ml and 0.25µg/ml using BMD and ≤1µg/ml and 2µg/ml using MGIT960 respectively. Microbiological failures occurred among BDQ exposed patients with a non-susceptible BDQ MIC, an Rv0678 mutation and ≤2 active drug classes. The Rv0678 RAVs were not the dominant mechanism of CFZ resistance and cross resistance was limited to isolates with an Rv0678 mutation. INTERPRETATION: Criteria for BDQ susceptibility are defined and will facilitate improved early detection of resistance. Cross- resistance between BDQ and CFZ is an emerging concern but in this study was primarily among those with an Rv0678 mutation.

Draft Genome Sequence of Mycobacterium peregrinum Isolated from an HIV-Positive Patient in South Africa.

Here, we report a draft genome sequence of Mycobacterium peregrinum obtained from a sputum sample of a South African HIV-infected patient with suspected pulmonary tuberculosis. The genome described here comprises 6,931,852 bp, revealing 66.2% G+C content, 6,808 coding sequences, and 81 RNA genes.