Silicosis, tuberculosis and silica exposure among artisanal and small-scale miners: A systematic review and modelling paper

An estimated 44 million artisanal and small-scale miners (ASM), largely based in developing economies, face significant occupational risks for respiratory diseases which have not been reviewed. We therefore aimed to review studies that describe silicosis and tuberculosis prevalence and respirable crystalline silica (RCS) exposures among ASM and use background evidence to better understand the relationship between exposures and disease outcomes. We searched PubMed, Web of Science, Scopus and Embase for studies published before the 24th March 2023. Our primary outcome of interest was silicosis or tuberculosis among ASM. Secondary outcomes included measurements of respirable dust or silica, spirometry and prevalence of respiratory symptoms. A systematic review and narrative synthesis was performed and risk of bias assessed using the Joanna Briggs Prevalence Critical Appraisal Tool. Logistic and Poisson regression models with predefined parameters were used to estimate silicosis prevalence and tuberculosis incidence at different distributions of cumulative silica exposure. We identified 18 eligible studies that included 29,562 miners from 13 distinct populations in 10 countries. Silicosis prevalence ranged from 11 to 37%, despite four of five studies reporting an average median duration of mining of <6 years. Tuberculosis prevalence was high; microbiologically confirmed disease ranged from 1.8 to 6.1% and clinical disease 3.0 to 17%. Average RCS intensity was very high (range 0.19-89.5 mg/m3) and respiratory symptoms were common. Our modelling demonstrated decreases in cumulative RCS are associated with reductions in silicosis and tuberculosis, with greater reductions at higher mean exposures. Despite potential selection and measurement bias, prevalence of silicosis and tuberculosis were high in the studies identified in this review. Our modelling demonstrated the greatest respiratory health benefits of reducing RCS are in those with highest exposures. ASM face a high occupational respiratory disease burden which can be reduced by low-cost and effective reductions in RCS.

A phase IIb, open-label, randomized controlled dose ranging multi-centre trial to evaluate the safety, tolerability, pharmacokinetics and exposure-response relationship of different doses of delpazolid in combination with bedaquiline delamanid moxifloxacin in adult subjects with newly diagnosed, uncomplicated, smear-positive, drug-sensitive pulmonary tuberculosis

BACKGROUND

Linezolid is an effective, but toxic anti-tuberculosis drug that is currently recommended for the treatment of drug-resistant tuberculosis. Improved oxazolidinones should have a better safety profile, while preserving efficacy. Delpazolid is a novel oxazolidinone developed by LegoChem Biosciences Inc. that has been evaluated up to phase 2a clinical trials. Since oxazolidinone toxicity can occur late in treatment, LegoChem Biosciences Inc. and the PanACEA Consortium designed DECODE to be an innovative dose-ranging study with long-term follow-up for determining the exposure-response and exposure-toxicity relationship of delpazolid to support dose selection for later studies. Delpazolid is administered in combination with bedaquiline, delamanid and moxifloxacin.

METHODS

Seventy-five participants with drug-sensitive, pulmonary tuberculosis will receive bedaquiline, delamanid and moxifloxacin, and will be randomized to delpazolid dosages of 0 mg, 400 mg, 800 mg, 1200 mg once daily, or 800 mg twice daily, for 16 weeks. The primary efficacy endpoint will be the rate of decline of bacterial load on treatment, measured by MGIT liquid culture time to detection from weekly sputum cultures. The primary safety endpoint will be the proportion of oxazolidinone class toxicities; neuropathy, myelosuppression, or tyramine pressor response. Participants who convert to negative liquid media culture by week 8 will stop treatment after the end of their 16-week course and will be observed for relapse until week 52. Participants who do not convert to negative culture will receive continuation phase treatment with rifampicin and isoniazid to complete a six-month treatment course.

DISCUSSION

DECODE is an innovative dose-finding trial, designed to support exposure-response modelling for safe and effective dose selection. The trial design allows assessment of occurrence of late toxicities as observed with linezolid, which is necessary in clinical evaluation of novel oxazolidinones. The primary efficacy endpoint is the change in bacterial load, an endpoint conventionally used in shorter dose-finding trials. Long-term follow-up after shortened treatment is possible through a safety rule excluding slow-and non-responders from potentially poorly performing dosages.

TRIAL REGISTRATION

DECODE was registered in ClinicalTrials.gov before recruitment start on 22 October 2021 (NCT04550832).

"Honestly, this problem has affected me a lot": a qualitative exploration of the lived experiences of people with chronic respiratory disease in Sudan and Tanzania

BACKGROUND

Over 500 million people live with chronic respiratory diseases globally and approximately 4 million of these, mostly from the low- and middle-income countries including sub-Saharan Africa, die prematurely every year. Despite high CRD morbidity and mortality, only very few studies describe CRDs and little is known about the economic, social and psychological dimensions of living with CRDs in sub-Saharan Africa. We aimed to gain an in-depth understanding of the social, livelihood and psychological dimensions of living with CRD to inform management of CRDs in Sudan and Tanzania.

METHOD

We conducted 12 in-depth interviews in 2019 with people with known or suspected CRD and 14 focus group discussions with community members in Gezira state, Sudan and Dodoma region, Tanzania, to share their understanding and experience with CRD. The data was analysed using thematic framework analysis.

RESULTS

People with CRD in both contexts reported experiences under two broad themes: impact on economic wellbeing and impact on social and psychological wellbeing. Capacity to do hard physical work was significantly diminished, resulting in direct and indirect economic impacts for them and their families. Direct costs were incurred while seeking healthcare, including expenditures on transportation to health facility and procurement of diagnostic tests and treatments, whilst loss of working hours and jobs resulted in substantial indirect costs. Enacted and internalised stigma leading to withdrawal and social exclusion was described by participants and resulted partly from association of chronic cough with tuberculosis and HIV/AIDS. In Sudan, asthma was described as having negative impact on marital prospects for young women and non-disclosure related to stigma was a particular issue for young people. Impaired community participation and restrictions on social activity led to psychological stress for both people with CRD and their families.

CONCLUSION

Chronic respiratory diseases have substantial social and economic impacts among people with CRD and their families in Sudan and Tanzania. Stigma is particularly strong and appears to be driven partly by association of chronic cough with infectiousness. Context-appropriate measures to address economic impacts and chronic cough stigma are urgently needed as part of interventions for chronic respiratory diseases in these sub-Saharan African contexts.

Clinical standards for drug-susceptible pulmonary TB

BACKGROUND: The aim of these clinical standards is to provide guidance on 'best practice´ for diagnosis, treatment and management of drug-susceptible pulmonary TB (PTB).METHODS: A panel of 54 global experts in the field of TB care, public health, microbiology, and pharmacology were identified; 46 participated in a Delphi process. A 5-point Likert scale was used to score draft standards. The final document represents the broad consensus and was approved by all 46 participants.RESULTS: Seven clinical standards were defined: Standard 1, all patients (adult or child) who have symptoms and signs compatible with PTB should undergo investigations to reach a diagnosis; Standard 2, adequate bacteriological tests should be conducted to exclude drug-resistant TB; Standard 3, an appropriate regimen recommended by WHO and national guidelines for the treatment of PTB should be identified; Standard 4, health education and counselling should be provided for each patient starting treatment; Standard 5, treatment monitoring should be conducted to assess adherence, follow patient progress, identify and manage adverse events, and detect development of resistance; Standard 6, a recommended series of patient examinations should be performed at the end of treatment; Standard 7, necessary public health actions should be conducted for each patient. We also identified priorities for future research into PTB.CONCLUSION: These consensus-based clinical standards will help to improve patient care by guiding clinicians and programme managers in planning and implementation of locally appropriate measures for optimal person-centred treatment for PTB.

Pharmacodynamic biomarkers for quantifying the mycobacterial effect of high doses of rifampin in patients with rifampin-susceptible pulmonary tuberculosis

Background

Suboptimal drug exposure in patients with drug-susceptible tuberculosis (DS-TB) can drive treatment failure. Pharmacodynamics (PD) biomarkers such as the plasma TB drug-activity (TDA) assay may guide dose finding studies and predict microbiological outcomes differently than conventional indices.

Methods

A study was nested from phase 2b randomized double-blind controlled trial of Tanzanian patients who received a 600 mg, 900 mg, or 1200 mg with a standard dose for DS-TB. Serum at 6 weeks collected over 24-h at 2-h intervals was collected for rifampin area under the concentration–time curve relative to minimum inhibitory concentration (AUC_0-24/MIC) or peak concentration and MIC (C_max/MIC). TDA was the ratio of time-to-positive growth of the patient’s Mycobacterium tuberculosis isolates with and without coculture of patient’s plasma collected at C_max. Spearman’s rank correlation (r) between PD parameters and culture convention on both liquid and solid culture media.

Results

Among 10 patients, 600 mg (3), 900 mg (3), and 1200 mg (4) of rifampin dosages. The mean ± standard deviation (SD) of AUC_0-24/MIC for patients on 600 mg was 168 ± 159 mg·h/L, on 900 mg was 169 ± 166 mg·h/L, and on 1200 mg was 308 ± 238 mg·h/L. The mean-TDA (SD) was 2.56 (±0.75), 1.5 (±0.59), and 2.29 (±1.08) for patients on 600 mg, 900 mg, and 1200 mg rifampin doses, respectively. Higher TDA values correlated with faster time to culture convention on both liquid (r =–0.55, P = 0.099) and solid media (r =–0.65, P = 0.04).

Conclusions

TDA and rifampin AUC_0-24/MIC did not trend as expected with rifampin dose, but TDA better predicted the time to sputum culture conversion. TDA may provide additional discrimination in predicting treatment response for some regimens distinct from plasma exposure relative to MIC or mg/kg dose.

Levofloxacin pharmacokinetics in saliva as measured by a mobile microvolume UV spectrophotometer among people treated for rifampicin-resistant TB in Tanzania

Background

Early detection and correction of low fluoroquinolone exposure may improve treatment of MDR-TB.

Objectives

To explore a recently developed portable, battery-powered, UV spectrophotometer for measuring levofloxacin in saliva of people treated for MDR-TB.

Methods

Patients treated with levofloxacin as part of a regimen for MDR-TB in Northern Tanzania had serum and saliva collected concurrently at 1 and 4 h after 2 weeks of observed levofloxacin administration. Saliva levofloxacin concentrations were quantified in the field via spectrophotometry, while serum was analysed at a regional laboratory using HPLC. A Bayesian population pharmacokinetics model was used to estimate the area under the concentration–time curve (AUC_0–24). Subtarget exposures of levofloxacin were defined by serum AUC_0–24 <80 mg·h/L. The study was registered at Clinicaltrials.gov with clinical trial identifier NCT04124055.

Results

Among 45 patients, 11 (25.6%) were women and 16 (37.2%) were living with HIV. Median AUC_0–24 in serum was 140 (IQR = 102.4–179.09) mg·h/L and median AUC_0–24 in saliva was 97.10 (IQR = 74.80–121.10) mg·h/L. A positive linear correlation was observed with serum and saliva AUC_0–24, and a receiver operating characteristic curve constructed to detect serum AUC_0–24 below 80 mg·h/L demonstrated excellent prediction [AUC 0.80 (95% CI = 0.62–0.94)]. Utilizing a saliva AUC_0–24 cut-off of 91.6 mg·h/L, the assay was 88.9% sensitive and 69.4% specific in detecting subtarget serum AUC_0–24 values, including identifying eight of nine patients below target.

Conclusions

Portable UV spectrophotometry as a point-of-care screen for subtarget levofloxacin exposure was feasible. Use for triage to other investigation or personalized dosing strategy should be tested in a randomized study.

A mobile microvolume UV/visible light spectrophotometer for the measurement of levofloxacin in saliva

INTRODUCTION

Therapeutic drug monitoring (TDM) for personalized dosing of fluoroquinolones has been recommended to optimize efficacy and reduce acquired drug resistance in the treatment of MDR TB. Therefore, the aim of this study was to develop a simple, low-cost, robust assay for TDM using mobile UV/visible light (UV/VIS) spectrophotometry to quantify levofloxacin in human saliva at the point of care for TB endemic settings.

METHODS

All experiments were performed on a mobile UV/VIS spectrophotometer. The levofloxacin concentration was quantified by using the amplitude of the second-order spectrum between 300 and 400 nm of seven calibrators. The concentration of spiked samples was calculated from the spectrum amplitude using linear regression. The method was validated for selectivity, specificity, linearity, accuracy and precision. Drugs frequently co-administered were tested for interference.

RESULTS

The calibration curve was linear over a range of 2.5-50.0 mg/L for levofloxacin, with a correlation coefficient of 0.997. Calculated accuracy ranged from -5.2% to 2.4%. Overall precision ranged from 2.1% to 16.1%. Application of the Savitsky-Golay method reduced the effect of interferents on the quantitation of levofloxacin. Although rifampicin and pyrazinamide showed analytical interference at the lower limit of quantitation of levofloxacin concentrations, this interference had no implication on decisions regarding the levofloxacin dose.

CONCLUSIONS

A simple UV/VIS spectrophotometric method to quantify levofloxacin in saliva using a mobile nanophotometer has been validated. This method can be evaluated in programmatic settings to identify patients with low levofloxacin drug exposure to trigger personalized dose adjustment.

TB or not TB? Definitive determination of species within the Mycobacterium tuberculosis complex in unprocessed sputum from adults with presumed multidrug-resistant tuberculosis

Objectives

Differences among Mycobacterium tuberculosis complex (MTC) species may predict drug resistance or treatment success. Thus, we optimised and deployed the genotype MTBC assay (gMTBC) to identify MTC to the species level, and then performed comparative genotypic drug‐susceptibility testing to anti‐tuberculosis drugs from direct sputum of patients with presumed multidrug‐resistant tuberculosis (MDR‐TB) by the MTBDRplus/sl reference method.

Methods

Patients with positive Xpert^® MTB/RIF (Xpert) results were consented to provide early‐morning‐sputum for testing by the gMTBC and the reference MTBDRplus/sl. Chi‐square or Fisher’s exact test compared proportions. Modified Poisson regression modelled detection of MTC by gMTBC.

Results

Among 73 patients, 53 (73%) were male and had a mean age of 43 (95% CI; 40–45) years. In total, 34 (47%), 36 (49%) and 38 (55%) had positive gMTBC, culture and MTBDR respectively. Forty patients (55%) had low quantity MTC by Xpert, including 31 (78%) with a negative culture. gMTBC was more likely to be positive in patients with chest cavity 4.18 (1.31–13.32, P = 0.016), high‐quantity MTC by Xpert 3.03 (1.35–6.82, P = 0.007) and sputum smear positivity 1.93 (1.19–3.14, P = 0.008). The accuracy of gMTBC in detecting MTC was 95% (95% CI; 86–98; κ = 0.89) compared to MTBDRplus/sl. All M. tuberculosis/canettii identified by gMTB were susceptible to fluoroquinolone and aminoglycosides/capreomycin.

Conclusions

The concordance between the gMTBC assay and MTBDRplus/sl in detecting MTC was high but lagged behind the yield of Xpert MTB/RIF. All M. tuberculosis/canettii were susceptible to fluoroquinolones, a core drug in MDR‐TB treatment regimens.

High burden of tuberculosis infection and disease among people receiving medication-assisted treatment for substance use disorder in Tanzania

OBJECTIVE

To determine the prevalence of tuberculosis (TB) disease and infection as well as incident TB disease among people who use drugs (PWUD) attending Medication Assisted Treatment (MAT) clinics in Dar-es-Salaam, Tanzania.

METHODS

In this prospective cohort study, a total of 901 consenting participants were enrolled from November 2016 to February 2017 and a structured questionnaire administered to them through the open data kit application on android tablets. Twenty-two months later, we revisited the MAT clinics and reviewed 823 of the 901 enrolled participant's medical records in search for documentation on TB disease diagnosis and treatment. Medical records reviewed included those of participants whom at enrolment were asymptomatic, not on TB disease treatment, not on TB preventive therapy and those who had a documented tuberculin skin test (TST) result.

RESULTS

Of the 823 medical records reviewed 22 months after enrolment, 42 had documentation of being diagnosed with TB disease and initiated on TB treatment. This is equivalent to a TB disease incidence rate of 2,925.2 patients per 100,000 person years with a total follow up time of 1,440 person-years. At enrolment the prevalence of TB disease and TB infection was 2.6% and 54% respectively and the HIV prevalence was 44% and 16% among females and males respectively.

CONCLUSION

PWUD attending MAT clinics bear an extremely high burden of TB and HIV and are known to have driven TB epidemics in a number of countries. Our reported TB disease incidence is 12 times that of the general Tanzanian incidence of 237 per 100,000 further emphasizing that this group should be prioritized for TB screening, testing and treatment. Gender specific approaches should also be developed as female PWUDs are markedly more affected with HIV and TB disease than male PWUDs.

Persistent chronic respiratory symptoms despite TB cure is poorly correlated with lung function

BACKGROUND: Persistent respiratory symptoms and lung function deficits are common after patients with TB. We aimed to define the burden of post-TB lung disease (PTLD) and assess associations between symptoms and impairment in two high TB incidence communities.METHODS: This was a cross-sectional survey of adults in Cape Town, South Africa who completed TB treatment 1-5 years previously. Questionnaires, spirometry and 6-minute walking distance (6MWD) were used to assess relationships between outcome measures and associated factors.RESULTS: Of the 145 participants recruited (mean age: 42 years, range: 18-75; 55 [38%] women), 55 (38%) had airflow obstruction and 84 (58%) had low forced vital capacity (FVC); the mean 6MWD was 463 m (range: 240-723). Respiratory symptoms were common: chronic cough (n = 27, 19%), wheeze (n = 61, 42%) and dyspnoea (modified MRC dyspnoea score 3 or 4: n = 36, 25%). There was poor correlation between FVC or obstruction and 6MWD. Only low body mass index showed consistent association with outcomes on multivariable analyses. Only 19 (13%) participants had a diagnosis of respiratory disease, and 16 (11%) currently received inhalers.CONCLUSION: There was substantial burden of symptoms and physiological impairment in this "cured" population, but poor correlation between objective outcome measures, highlighting deficits in our understanding of PTLD.

Determination of Rifampin Concentrations by Urine Colorimetry and Mobile Phone Readout for Personalized Dosing in Tuberculosis Treatment

BACKGROUND

Individual pharmacokinetic variability is a driver of poor tuberculosis (TB) treatment outcomes. We developed a method for measurement of rifampin concentrations by urine colorimetry and a mobile phone photographic application to predict clinically important serum rifampin pharmacokinetic measurements in children treated for TB.

METHODS

Among spiked urine samples, colorimetric assay performance was tested with conventional spectrophotometric and the mobile phone/light box methods under various environmental and biologic conditions. Urine rifampin absorbance (Abs) was then determined from timed specimens from children treated for TB in Tanzania, and compared to serum pharmacokinetic measurements collected throughout the dosing interval.

RESULTS

Both the mobile phone/light box and spectrophotometry demonstrated excellent correlation across a wide range of urine rifampin concentrations (7.8-1000 mg/L) in intra- and interday trials, 24-hour exposure to ambient light or darkness, and varying urinalysis profiles (all r ≥ 0.98). In 12 Tanzanian children, the urine mobile phone/light box measurement and serum peak concentration (Cmax) were significantly correlated (P = .004). Using a Cmax target of 8 mg/L, the area under the receiver operating characteristic curve was 80.1% (range, 47.2%-100%). A urine mobile phone/light box threshold of 50 Abs correctly classified all patients (n = 6) with serum measurements below target.

CONCLUSIONS

The urine colorimetry with mobile phone/light box assay accurately measured rifampin absorbance in varying environmental and biological conditions that may be observed clinically. Among children treated for TB, the assay was sensitive for detection of low rifampin serum concentrations. Future work will identify the optimal timing for urine collection, and operationalize use in TB-endemic settings.

Post-tuberculosis lung health: perspectives from the First International Symposium

ALTHOUGH CURABLE, TB frequently leaves the individual with chronic physical and psycho-social impairment, but these consequences have been largely neglected. The 1^st International Post-Tuberculosis Symposium (Stellenbosch, South Africa) was held to discuss priorities and gaps in addressing this issue. A barrier to progress has been the varied terminology and nomenclature, so the Delphi process was used to achieve consensus on definitions. Lack of sufficient evidence hampered definitive recommendations in most domains, including prevention and treatment of post-TB lung disease (PTLD), but the discussions clarified the research needed. A consensus was reached on a toolkit for future PTLD measurement and on PTLD patterns to be considered. The importance of extra-pulmonary consequences and progressive impairment throughout the life-course was identified, including TB recurrence and increased mortality. Patient advocates emphasised the need to address the psychological and social impacts post TB and called for clinical guidance. More generally, there is an urgent need for increased awareness and research into post-TB complications.

Clinical outcomes of new algorithm for diagnosis and treatment of Tuberculosis sepsis in HIV patients

Background

Despite effort to diagnose tuberculosis (TB) in the Human Immunodeficiency Virus (HIV) infected population, 45% of adults with HIV that had a previously unknown reason for death, demonstrated TB was the cause by autopsy examination. We aimed to assess the clinical outcomes of implementation a new algorithm for diagnosis and treatment of tuberculosis (TB) related sepsis among PLHIV presenting with life-threatening illness.

Methods

This study is a prospective cohort conducted in three-referral hospitals in Kilimanjaro, recruited 97 PLHIV from February through June 2018. Patients provided urine and sputum samples for testing lateral flow - lipoarabinomannan (LF-LAM) and Xpert Mycobacterium tuberculosis (MTB)/rifampicin (RIF) assays, respectively. Anti-TB was prescribed to patients with positive LF-LAM or Xpert MTB/RIF or received broad-spectrum antibiotics but deteriorated.

Results

Of 97 patients, 84 (87%) provided urine and sputa, and 13 (13%) provided only urine. The mean age (95% confidence interval) was 40 (38-43) years and 52 (54%) were female. In 84 patients, LF-LAM increased TB detection from 26 (31%) by Xpert MTB/RIF to 41 (55%) by both tests. Of 97 patients, 69 (71%) prescribed anti-TB, 67% (46/69) and 33% (23/69) had definitive and probable TB respectively. Sixteen (16.5%) patients died, of which one died before treatment, 73% (11/15) died within 7 days of admission. The 30-day survival was similar in both treatment groups (log rank = 0.1574). Mortality was significantly higher among hospitalized patients compared to outpatients (P ≤ 0.027).

Conclusion

Implementation of new algorithm increased TB case detection in patients that could have been missed by Xpert MTB/RIF assay. Survival of PLHIV with confirmed or probable TB was comparable to those of PLHIV that were treated with broad-spectrum antibiotics alone. Further work should focus on the optimal timing and content of the immediate antimicrobial regimen for sepsis among PLHIV in TB-endemic settings.

Whole genome sequencing of Mycobacterium tuberculosis isolates and clinical outcomes of patients treated for multidrug-resistant tuberculosis in Tanzania

BACKGROUND

Tuberculosis (TB), particularly multi- and or extensive drug resistant TB, is still a global medical emergency. Whole genome sequencing (WGS) is a current alternative to the WHO-approved probe-based methods for TB diagnosis and detection of drug resistance, genetic diversity and transmission dynamics of Mycobacterium tuberculosis complex (MTBC). This study compared WGS and clinical data in participants with TB.

RESULTS

This cohort study performed WGS on 87 from MTBC DNA isolates, 57 (66%) and 30 (34%) patients with drug resistant and susceptible TB, respectively. Drug resistance was determined by Xpert® MTB/RIF assay and phenotypic culture-based drug-susceptibility-testing (DST). WGS and bioinformatics data that predict phenotypic resistance to anti-TB drugs were compared with participant's clinical outcomes. They were 47 female participants (54%) and the median age was 35 years (IQR): 29-44). Twenty (23%) and 26 (30%) of participants had TB/HIV co-infection BMI < 18 kg/m2 respectively. MDR-TB participants had MTBC with multiple mutant genes, compared to those with mono or polyresistant TB, and the majority belonged to lineage 3 Central Asian Strain (CAS). Also, MDR-TB was associated with delayed culture-conversion (median: IQR (83: 60-180 vs. 51:30-66) days). WGS had high concordance with both culture-based DST and Xpert® MTB/RIF assay in detecting drug resistance (kappa = 1.00).

CONCLUSION

This study offers comparison of mutations detected by Xpert and WGS with phenotypic DST of M. tuberculosis isolates in Tanzania. The high concordance between the different methods and further insights provided by WGS such as PZA-DST, which is not routinely performed in most resource-limited-settings, provides an avenue for inclusion of WGS into diagnostic matrix of TB including drug-resistant TB.

OC 8717 TRANSFER OF LEADERSHIP, WHAT DO WE NEED?

Background

The Pan African Consortium for the Evaluation of Anti-Tuberculosis Antibiotics (PanACEA) was designed to build clinical tuberculosis (TB) trial capacity whilst conducting clinical trials investigating novel and existing agents to shorten and simplify TB treatment. One of the objectives of the programme is to foster leadership development in sub-Saharan TB-endemic countries to move leadership to African partners in the PanACEA research programmes.

Methods and results

In PanACEA 1 the participation of the sites on the consortium board was important to foster leadership development. African investigators now make up a large part of the consortium leadership and are actively developing new concepts. Delegates of the sites visited the annual PanACEA General Assembly meetings, where they could gain knowledge, actively participate in the meetings and discussions and network with others from the TB research community. Various sites participated at TB research community conferences (e.g. CROI, Lung Health Meeting) where PanACEA members gave presentations and could collaborate with other TB trial networks.

In PanACEA 2 all clinical trials are co-led by a European established researcher and an African Principal Investigator (PI), to ensure that African scientists are trained and mentored to lead in every aspect essential to clinical trial delivery, from trial and data management to statistical analysis and trial design, and from financial management to laboratory science. The capacity development cores, which serve as operational support for all PanACEA studies and provide high level oversight, also use the European and African countersystem, including senior and junior co-chairs among the African trial sites.

An example of leadership transfer is a large EDCTP application for the development of a new compound in MDR TB (FACE-MDR-TB) in which Stellah Mpagama is the lead applicant.

Conclusion

The PanACEA consortium has actively facilitated a transfer of leadership programme which may be successful in future consortia.

Evaluation of cytokines in peripheral blood mononuclear cell supernatants for the diagnosis of tuberculosis

INTRODUCTION

There is active interest in leveraging host immune responses as biomarkers of tuberculosis (TB) disease activity. We had previously evaluated an immunodiagnostic test called the antibody in lymphocyte supernatant (ALS) assay. Here, we aimed to evaluate a panel of inflammatory mediators and associate the responses with the ALS results to identify a biosignature to distinguish TB cases from controls.

METHODOLOGY

In this case-control study, adults with TB were compared to controls who were hospitalized for non-infectious conditions. Blood was collected at baseline and after 4 weeks of TB treatment (from TB cases only). Peripheral blood mononuclear cells were isolated and cultured without antigenic stimulation for 72 hours. Inflammatory mediators were measured using the Multiplex cytokine kit and compared between TB cases and controls; among TB cases, responses were compared over time. ALS and inflammatory mediator results were evaluated using generalized discriminant analysis to identify the optimal biosignature to predict TB.

RESULTS

When comparing inflammatory mediators between groups, IL-1ra, IL-1β, and granulocyte macrophage-colony stimulating factor (GM-CSF) were lower in TB cases (P<0.002). Fibroblast growth factor-basic significantly increased from baseline to week-4 (P=0.002). Generalized discriminant analysis yielded a model with IL-2, tumor necrosis factor-alpha, vascular endothelial growth factor, and ALS, providing a sensitivity of 82.2% and specificity of 76.2%.

CONCLUSION

Our results suggest that IL-1ra, IL-1β, and GM-CSF might be used as diagnostic biomarkers to distinguish between TB cases and non-TB cases. We could not identify a group of mediators that outperformed the diagnostic accuracy of the ALS alone.

Population Pharmacokinetic Model and Limited Sampling Strategies for Personalized Dosing of Levofloxacin in Tuberculosis Patients

Levofloxacin is an antituberculosis drug with substantial interindividual pharmacokinetic variability; therapeutic drug monitoring (TDM) could therefore be helpful to improve treatment results. TDM would be more feasible with limited sampling strategies (LSSs), a method to estimate the area under the concentration curve for the 24-h dosing interval (AUC0-24) by using a limited number of samples. This study aimed to develop a population pharmacokinetic (popPK) model of levofloxacin in tuberculosis patients, along with LSSs using a Bayesian and multiple linear regression approach. The popPK model and Bayesian LSS were developed using data from 30 patients and externally validated with 20 patients. The LSS based on multiple linear regression was internally validated using jackknife analysis. Only clinically suitable LSSs (maximum time span, 8 h; minimum interval, 1 h; 1 to 3 samples) were tested. Performance criteria were root-mean-square error (RMSE) of <15%, mean prediction error (MPE) of <5%, and r2 value of >0.95. A one-compartment model with lag time best described the data while only slightly underestimating the AUC0-24 (mean, -7.9%; standard error [SE], 1.7%). The Bayesian LSS using 0- and 5-h postdose samples (RMSE, 8.8%; MPE, 0.42%; r2 = 0.957) adequately estimated the AUC0-24, with a mean underestimation of -4.4% (SE, 2.7%). The multiple linear regression LSS using 0- and 4-h postdose samples (RMSE, 7.0%; MPE, 5.5%; r2 = 0.977) was internally validated, with a mean underestimation of -0.46% (SE, 2.0%). In this study, we successfully developed a popPK model and two LSSs that could be implemented in clinical practice to assist TDM of levofloxacin. (This study has been registered at ClinicalTrials.gov under identifier NCT01918397.).

Phenotypic Changes on Mycobacterium Tuberculosis-Specific CD4 T Cells as Surrogate Markers for Tuberculosis Treatment Efficacy

Background: The analysis of phenotypic characteristics on Mycobacterium tuberculosis (MTB)-specific T cells is a promising approach for the diagnosis of active tuberculosis (aTB) and for monitoring treatment success. We therefore studied phenotypic changes on MTB-specific CD4 T cells upon anti-tuberculosis treatment initiation in relation to the treatment response as determined by sputum culture. Methods: Peripheral blood mononuclear cells from subjects with latent MTB infection (n = 16) and aTB (n = 39) at baseline, weeks 9, 12, and 26 (end of treatment) were analyzed after intracellular interferon gamma staining and overnight stimulation with tuberculin. Liquid sputum cultures were performed weekly until week 12 and during 4 visits until week 26. Results: T cell activation marker expression on MTB-specific CD4 T cells differed significantly between subjects with aTB and latent MTB infection with no overlap for the frequencies of CD38^pos and Ki67^pos cells (both p < 0.0001). At 9 weeks after anti-TB treatment initiation the frequencies of activation marker (CD38, HLA-DR, Ki67) positive MTB-specific, but not total CD4 T cells, were significantly reduced (p < 0.0001). Treatment induced phenotypic changes from baseline until week 9 and until week 12 differed substantially between individual aTB patients and correlated with an individual's time to stable sputum culture conversion for expression of CD38 and HLA-DR (both p < 0.05). In contrast, the frequencies of maturation marker CD27 positive MTB-specific CD4 T cells remained largely unchanged until week 26 and significantly differed between subjects with treated TB disease and latent MTB infection (p = 0.0003). Discussion: Phenotypic changes of MTB-specific T cells are potential surrogate markers for tuberculosis treatment efficacy and can help to discriminate between aTB (profile: CD38^pos, CD27^low), treated TB (CD38^neg, CD27^low), and latent MTB infection (CD38^neg, CD27^high).

Platelet-monocyte interaction in Mycobacterium tuberculosis infection

The immune effects of platelets and platelet-leukocyte aggregation are increasingly recognized. We studied the occurrence of platelet-monocyte aggregation (PMA) in patients with pulmonary tuberculosis (TB), the processes underlying PMA and consequences for cytokine responses. In a cross-sectional study involving 65 Tanzanian TB patients in different phases of treatment and 29 healthy controls, TB patients had a significantly higher PMA. This increased PMA in TB patients was associated with increased monocyte CCR5, CD16 expression and PF4, but not with increased membrane-expressed or soluble P-selectin expression. These findings were confirmed in vitro: whereas incubation of whole blood with Mycobacterium tuberculosis (Mtb) did not activate platelets, monocytes became activated with higher CD11b, CD16 and CCR5 expression, but this was independent of platelet-monocyte interaction. Still, platelets had an anti-inflammatory effect on cytokine responses as peripheral blood mononuclear cells (PBMC) incubated with Mtb in the presence of platelets produced less interleukin (IL)-1β, tumor necrosis factor-α, IL-6 and interferon-γ and more IL-10. In conclusion, increased PMA during TB infection is caused by monocyte and not platelet activation. By counteracting the Mtb-induced pro-inflammatory leukocyte response, platelets may protect against excessive tissue damage, but may also compromise the production of protective cytokines, such as IFNƴ and TNFα.

Prevalence and extent of heteroresistance by next generation sequencing of multidrug-resistant tuberculosis

Amplicon-based Next Generation Sequencing (NGS) is an emerging method for Mycobacterium tuberculosis drug susceptibility testing (DST) but has not been well described. We examined 158 clinical multidrug-resistant M. tuberculosis isolates via NGS of 11 resistance-associated gene regions covering 3519 nucleotides. Across these gene regions, complete resistance or heteroresistance (defined as 1%-99% mutation) was present in at least one isolate in 6.3% of loci. The number of isolates with heteroresistance was highest for gyrA codon 94, rpoB codons 526 and 531, and embB codons 306, 372 and 406 (range 11-26% of isolates exhibited heteroresistance). 57% of MDR strains had heteroresistance of one or more recognized resistance-associated mutation. Heteroresistant loci generally exhibited high or low degrees of mutation (>90% or <10%). The deep sensitivity of NGS for detecting low level pncA heteroresistance appeared to improve genotypic-phenotypic PZA susceptibility correlations over that of Sanger. NGS demonstrates that heteroresistance in TB in the regions of key genes is common and will need to be bioinformatically managed. The clinical significance of such heteroresistance is unclear, and further study of pncA should be pursued.

Determination of plasma concentrations of levofloxacin by high performance liquid chromatography for use at a multidrug-resistant tuberculosis hospital in Tanzania

Therapeutic drug monitoring may improve multidrug-resistant tuberculosis (MDR-TB) treatment outcomes. Levofloxacin demonstrates significant individual pharmacokinetic variability. Thus, we sought to develop and validate a high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection for levofloxacin in patients on MDR-TB treatment. The HPLC-UV method is based on a solid phase extraction (SPE) and a direct injection into the HPLC system. The limit of quantification was 0.25 μg/mL, and the assay was linear over the concentration range of 0.25—15 μg/mL (y = 0.5668x—0.0603, R² = 0.9992) for the determination of levofloxacin in plasma. The HPLC-UV methodology achieved excellent accuracy and reproducibility along a clinically meaningful range. The intra-assay RSD% of low, medium, and high quality control samples (QC) were 1.93, 2.44, and 1.90, respectively, while the inter-assay RSD% were 3.74, 5.65, and 3.30, respectively. The mean recovery was 96.84%. This method was then utilized to measure levofloxacin concentrations from patients’ plasma samples from a retrospective cohort of consecutive enrolled subjects treated for MDR-TB at the national TB hospital in Tanzania during 5/3/2013–8/31/2015. Plasma was collected at 2 hours after levofloxacin administration, the time of estimated peak concentration (eC_max) treatment. Forty-one MDR-TB patients had plasma available and 39 had traceable programmatic outcomes. Only 13 (32%) patients had any plasma concentration that reached the lower range of the expected literature derived C_max with the median eC_max being 5.86 (3.33–9.08 μg/ml). Using Classification and Regression Tree analysis, an eC_max ≥7.55 μg/mL was identified as the threshold which best predicted cure. Analyzing this CART derived threshold on treatment outcome, the time to sputum culture conversion was 38.3 ± 22.7 days vs. 47.8 ± 26.5 days (p = 0.27) and a greater proportion were cured, in 10 out of 15 (66.7%) vs. 6 out of 18 (33.3%) (p = 0.06) respectively. Furthermore, one patient with an eC_max/minimum inhibitory concentration (MIC) of only 1.13 acquired extensively drug resistant (XDR)-TB while undergoing treatment. The individual variability of levofloxacin concentrations in MDR-TB patients from Tanzania supports further study of the application of onsite therapeutic drug monitoring and MIC testing.