Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles.

Interrupting transmission events to prevent new acquisition of infection and disease is a critical part of tuberculosis (TB) control efforts. However, knowledge gaps in understanding the biology and determinants of TB transmission, including poor estimates of individual infectiousness and the lack of accurate and convenient biomarkers, undermine efforts to develop interventions. Cough-generated aerosol cultures have been found to predict TB transmission better than any microbiological or clinical markers in cohorts from Uganda and Brazil. We hypothesized that highly infectious individuals with pulmonary TB (defined as positive for cough aerosol cultures) have elevated inflammatory markers and unique transcriptional profiles compared to less infectious individuals (negative for cough aerosol cultures). We performed a prospective, longitudinal study using a cough aerosol sampling system as in other studies. We enrolled 142 participants with treatment-naïve pulmonary TB in Nairobi, Kenya, and assessed the association of clinical, microbiologic, and immunologic characteristics with Mtb aerosolization and transmission in 143 household members. Contacts of the forty-three aerosol culture-positive participants (30%) were more likely to have a positive IGRA (85% vs 53%, P = 0.005) and a higher median IGRA IFNγ level (P < 0.001, median 4.25 IU/ml (0.90-5.91) vs. 0.71 (0.01-3.56)) compared to aerosol culture-negative individuals. We found that higher bacillary burden, younger age, and larger mean upper arm circumference were associated with positive aerosol cultures. In addition, novel host inflammatory profiles, including elevated serum C-reactive protein and sputum cytokines, were associated with aerosol culture status. Notably, we found pre-treatment whole blood transcriptional profiles associated with aerosol culture status, independent of bacillary load. Together, these findings suggest that TB infectiousness is associated with epidemiologic characteristics and inflammatory signatures and that these features may be used to identify highly infectious persons. These results provide new public health tools and insights into TB pathogenesis.

TBscreen: A passive cough classifier for tuberculosis screening with a controlled dataset.

Recent respiratory disease screening studies suggest promising performance of cough classifiers, but potential biases in model training and dataset quality preclude robust conclusions. To examine tuberculosis (TB) cough diagnostic features, we enrolled subjects with pulmonary TB (N = 149) and controls with other respiratory illnesses (N = 46) in Nairobi. We collected a dataset with 33,000 passive coughs and 1600 forced coughs in a controlled setting with similar demographics. We trained a ResNet18-based cough classifier using images of passive cough scalogram as input and obtained a fivefold cross-validation sensitivity of 0.70 (±0.11 SD). The smartphone-based model had better performance in subjects with higher bacterial load {receiver operating characteristic-area under the curve (ROC-AUC): 0.87 [95% confidence interval (CI): 0.87 to 0.88], P < 0.001} or lung cavities [ROC-AUC: 0.89 (95% CI: 0.88 to 0.89), P < 0.001]. Overall, our data suggest that passive cough features distinguish TB from non-TB subjects and are associated with bacterial burden and disease severity.

Sensitive Blood-Based Detection of HIV-1 and Mycobacterium tuberculosis Peptides for Disease Diagnosis by Immuno-Affinity Liquid Chromatography-Tandem Mass Spectrometry: A Method Development and Proof-of-Concept Study.

BACKGROUND: Novel approaches that allow early diagnosis and treatment monitoring of both human immunodeficiency virus-1 (HIV-1) and tuberculosis disease (TB) are essential to improve patient outcomes. METHODS: We developed and validated an immuno-affinity liquid chromatography-tandem mass spectrometry (ILM) assay that simultaneously quantifies single peptides derived from HIV-1 p24 and Mycobacterium tuberculosis (Mtb) 10-kDa culture filtrate protein (CFP10) in trypsin-digested serum derived from cryopreserved serum archives of cohorts of adults and children with/without HIV and TB. RESULTS: ILM p24 and CFP10 results demonstrated good intra-laboratory precision and accuracy, with recovery values of 96.7% to 104.6% and 88.2% to 111.0%, total within-laboratory precision (CV) values of 5.68% to 13.25% and 10.36% to 14.92%, and good linearity (r2 > 0.99) from 1.0 to 256.0 pmol/L and 0.016 to 16.000 pmol/L, respectively. In cohorts of adults (n = 34) and children (n = 17) with HIV and/or TB, ILM detected p24 and CFP10 demonstrated 85.7% to 88.9% and 88.9% to 100.0% diagnostic sensitivity for HIV-1 and TB, with 100% specificity for both, and detected HIV-1 infection earlier than 3 commercial p24 antigen/antibody immunoassays. Finally, p24 and CFP10 values measured in longitudinal serum samples from children with HIV-1 and TB distinguished individuals who responded to TB treatment from those who failed to respond or were untreated, and who developed TB immune reconstitution inflammatory syndrome. CONCLUSIONS: Simultaneous ILM evaluation of p24 and CFP10 results may allow for early TB and HIV detection and provide valuable information on treatment response to facilitate integration of TB and HIV diagnosis and management.

Diagnostic Advances in Childhood Tuberculosis-Improving Specimen Collection and Yield of Microbiological Diagnosis for Intrathoracic Tuberculosis.

There is no microbiological gold standard for childhood tuberculosis (TB) diagnosis. The paucibacillary nature of the disease, challenges in sample collection in young children, and the limitations of currently available microbiological tests restrict microbiological confirmation of intrathoracic TB to the minority of children. Recent WHO guidelines recommend the use of novel rapid molecular assays as initial diagnostic tests for TB and endorse alternative sample collection methods for children. However, the uptake of these tools in high-endemic settings remains low. In this review, we appraise historic and new microbiological tests and sample collection techniques that can be used for the diagnosis of intrathoracic TB in children. We explore challenges and possible ways to improve diagnostic yield despite limitations, and identify research gaps to address in order to improve the microbiological diagnosis of intrathoracic TB in children.

The Incidence of Non-Tuberculous Mycobacteria in Infants in Kenya.

There is inadequate understanding of the epidemiology of Non-Tuberculous Mycobacteria (NTM) among infants in high tuberculosis burden countries. The objective of this study was to document the incidence and diversity of NTM disease or colonisation in sputum specimens from infants with presumptive TB, the risk factors, and clinical characteristics, in a high TB and HIV burden setting in Western Kenya. A cohort of 2900 newborns was followed for 1-2 years to assess TB incidence. TB investigations included collection of induced sputa and gastric aspirates for culture and speciation by HAIN®, Tuberculin Skin Testing (TST), HIV testing, and chest radiography. The American Thoracic Society Criteria (ATS) were applied to identify NTM disease. Among 927 (32% of 2900) with presumptive TB, 742 (80%) were investigated. NTM were isolated from 19/742 (2.6%) infants. M. fortuitum was most frequently speciated (32%). Total person-time was 3330 years. NTM incidence was 5.7/1,000 person-years, 95% CI (3.5, 8.7). Infants diagnosed with TB were more likely to have NTM isolation (odds ratio 11.5; 95% CI 3.25, 41.0). None of the infants with NTM isolated met the criteria for NTM disease. The incidence of NTM isolation was comparable to similar studies in Africa. NTM isolation did not meet ATS criteria for disease and could represent colonisation. TB disease appears to be structural lung disease predisposing to NTM colonisation.

Development of colorimetric sensor array for diagnosis of tuberculosis through detection of urinary volatile organic compounds.

BACKGROUND: Top priorities for tuberculosis control and elimination include a simple, low-cost screening test using sputum and a non-sputum-based test in patients that do not produce sputum. The aim of this study was to evaluate the performance of a colorimetric sensor array (CSA) test, for analysis of volatile organic compounds in urine, in the diagnosis of pulmonary TB. MATERIAL AND METHODS: Urine samples were collected from individuals suspected of having pulmonary TB in Western Kenya. Reference methods included MGIT culture and/or Xpert MTB/RIF nucleic acid amplification test on sputa. Fresh urine samples were tested with the CSA, with acid and base and without an additive. The CSA were digitally imaged, and the resulting colorimetric response patterns were used for chemometric analysis. Sensitivity, specificity, and negative (NPV) and positive predictive (PPV) values were determined for HIV-positive and HIV-negative patients. RESULTS: In HIV-negative patients, the highest accuracy was obtained in urine samples pre-treated with a base, yielding a sensitivity, specificity, PPV, and NPV of 78.3% (65/83), 69.2% (54/78), 73.0% (n/89) and 75.0% (n/72). The highest sensitivity of 79.5% was achieved using sensor data from all three test conditions at a specificity of 65.4%. In HIV-positive subjects, the sensor performance was substantially lower with sensitivity, specificity, PPV, and NPV ranging from 48.3% to 62.3%, 54.1% to 74.0%, 55.9% to 64.2%, and 60.6% to 64.9%, respectively. CONCLUSION: The CSA fingerprint of urine headspace volatiles showed moderate accuracy in diagnosing TB in HIV-negative patients, but the sensor performance dropped substantially in HIV-coinfected patients. Further development of TB-responsive CSA indicators may improve the accuracy of CSA urine assay.

Xpert MTB/RIF Ultra for detection of Mycobacterium tuberculosis and rifampicin resistance: a prospective multicentre diagnostic accuracy study.

BACKGROUND: The Xpert MTB/RIF assay is an automated molecular test that has improved the detection of tuberculosis and rifampicin resistance, but its sensitivity is inadequate in patients with paucibacillary disease or HIV. Xpert MTB/RIF Ultra (Xpert Ultra) was developed to overcome this limitation. We compared the diagnostic performance of Xpert Ultra with that of Xpert for detection of tuberculosis and rifampicin resistance. METHODS: In this prospective, multicentre, diagnostic accuracy study, we recruited adults with pulmonary tuberculosis symptoms presenting at primary health-care centres and hospitals in eight countries (South Africa, Uganda, Kenya, India, China, Georgia, Belarus, and Brazil). Participants were allocated to the case detection group if no drugs had been taken for tuberculosis in the past 6 months or to the multidrug-resistance risk group if drugs for tuberculosis had been taken in the past 6 months, but drug resistance was suspected. Demographic information, medical history, chest imaging results, and HIV test results were recorded at enrolment, and each participant gave at least three sputum specimen on 2 separate days. Xpert and Xpert Ultra diagnostic performance in the same sputum specimen was compared with culture tests and drug susceptibility testing as reference standards. The primary objectives were to estimate and compare the sensitivity of Xpert Ultra test with that of Xpert for detection of smear-negative tuberculosis and rifampicin resistance and to estimate and compare Xpert Ultra and Xpert specificities for detection of rifampicin resistance. Study participants in the case detection group were included in all analyses, whereas participants in the multidrug-resistance risk group were only included in analyses of rifampicin-resistance detection. FINDINGS: Between Feb 18, and Dec 24, 2016, we enrolled 2368 participants for sputum sampling. 248 participants were excluded from the analysis, and 1753 participants were distributed to the case detection group (n=1439) and the multidrug-resistance risk group (n=314). Sensitivities of Xpert Ultra and Xpert were 63% and 46%, respectively, for the 137 participants with smear-negative and culture-positive sputum (difference of 17%, 95% CI 10 to 24); 90% and 77%, respectively, for the 115 HIV-positive participants with culture-positive sputum (13%, 6·4 to 21); and 88% and 83%, respectively, across all 462 participants with culture-positive sputum (5·4%, 3·3 to 8·0). Specificities of Xpert Ultra and Xpert for case detection were 96% and 98% (-2·7%, -3·9 to -1·7) overall, and 93% and 98% for patients with a history of tuberculosis. Xpert Ultra and Xpert performed similarly in detecting rifampicin resistance. INTERPRETATION: For tuberculosis case detection, sensitivity of Xpert Ultra was superior to that of Xpert in patients with paucibacillary disease and in patients with HIV. However, this increase in sensitivity came at the expense of a decrease in specificity. FUNDING: Government of Netherlands, Government of Australia, Bill & Melinda Gates Foundation, Government of the UK, and the National Institute of Allergy and Infectious Diseases.