Diagnostic utility of bronchoalveolar lavage in children with complicated intrathoracic tuberculosis

INTRODUCTION

Bronchoscopy can be a useful tool in children with pulmonary tuberculosis (PTB) with severe disease potentially requiring intervention or in the face of diagnostic dilemmas. The aim of this study was to determine the value of Xpert MTB/RIF assay (Xpert) on bronchoalveolar lavage (BAL) samples in children with complicated PTB.

METHODS

Retrospective analysis of children with clinically diagnosed PTB, who underwent routine bronchoscopy over a 5-year period at a large referral hospital. BAL and other respiratory samples were tested by microscopy, culture, and Xpert. We explored whether clinical, radiographic and bronchoscopy findings, and duration of antituberculosis treatment were associated with bacteriological confirmation.

RESULTS

One hundred and twelve out of one hundred and forty-six (76.7%) children (median age 16 months) were on antituberculosis treatment for a median of 10 days at the time of bronchoscopy. Overall, bacteriological confirmation was achieved in 115 (78.7%), with 101 (69.2%) detected on BAL. Of those bacteriologically confirmed on BAL, 61.4% were positive by both Xpert and culture, 34.7% only by Xpert, and 3.9% only by culture. Sensitivity and specificity of Xpert compared with culture on BAL samples for children not on antituberculosis treatment were 94.1% (95% confidence interval [CI]: 71.3, 99.8) and 68.7% (95% CI: 41.3, 89.0), respectively.

CONCLUSIONS

In children undergoing bronchoscopy for complicated PTB, Xpert testing of BAL had a high diagnostic yield in children already on antituberculosis treatment. Bronchoscopy should be considered if noninvasive respiratory specimens fail to confirm complicated TB.

Comparing rates of mycobacterial clearance in sputum smear-negative and smear-positive adults living with HIV

Background

Pulmonary tuberculosis (TB) in people living with HIV (PLH) frequently presents as sputum smear-negative. However, clinical trials of TB in adults often use smear-positive individuals to ensure measurable bacterial responses following initiation of treatment, thereby excluding HIV-infected patients from trials.

Methods

In this prospective case cohort study, 118 HIV-seropositive TB patients were assessed prior to initiation of standard four-drug TB therapy and at several time points through 35 days. Sputum bacillary load, as a marker of treatment response, was determined serially by: smear microscopy, Xpert MTB/RIF, liquid culture, and colony counts on agar medium.

Results

By all four measures, patients who were baseline smear-positive had higher bacterial loads than those presenting as smear-negative, until day 35. However, most smear-negative PLH had significant bacillary load at enrolment and their mycobacteria were cleared more rapidly than smear-positive patients. Smear-negative patients’ decline in bacillary load, determined by colony counts, was linear to day 7 suggesting measurable bactericidal activity. Moreover, the decrease in bacterial counts was comparable to smear-positive individuals. Increasing cycle threshold values (Ct) on the Xpert assay in smear-positive patients to day 14 implied decreasing bacterial load.

Conclusion

Our data suggest that smear-negative PLH can be included in clinical trials of novel treatment regimens as they contain sufficient viable bacteria, but allowances for late exclusions would have to be made in sample size estimations. We also show that increases in Ct in smear-positive patients to day 14 reflect treatment responses and the Xpert MTB/RIF assay could be used as biomarker for early treatment response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06133-4.

Comparison of isothermal microcalorimetry and BACTEC MGIT960 for the detection of the metabolic activity of Mycobacterium tuberculosis in sputum samples

INTRODUCTION

This study explores the uses of microcalorimetry to detect Mycobacterium tuberculosis (TB) in sputum. Microcalorimetry measures metabolic heat evolution during cellular proliferation of tuberculosis (TB) and is considered as a possible alternative to conventional diagnostic tools.

OBJECTIVES

To compare the time to detection (TTD) from the BACTEC™ MGIT™ 960 and the calScreener™ calorimetric system.

METHODS

Sixty-four sputa samples were selected from patients with confirmed pulmonary tuberculosis. Those sample were then decontaminated and analysed using calorimetry and BACTEC MGIT 960 system.

RESULTS

The incubation period until detection of M. tuberculosis in the sample was 8·5 ± 3·7 days for the MGIT system and 10·1 ± 4·1 days (mean ± SD) for calorimetry.

CONCLUSIONS

The microincubations in the 48-well format calScreener offers potential for rapid and accurate diagnostic of TB in different samples. Although TTD from calorimetry is still longer than with the MGIT, our findings suggest that several improvements are possible. Still, the instrument is ideal for continuous, real-time analysis of net metabolic heat release of limited sample numbers.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our result emphasizes that with further optimization, calorimetry can become an alternative detection method for tuberculosis.

Liquid mycobacterial culture outcomes after different sputum collection techniques before and during treatment

SETTING

Mycobacterial sputum culture is a key diagnostic and research tool.

OBJECTIVE

To compare mycobacterial culture outcomes of three sputum collection methods.

DESIGN

We compared culture results within sets of three sputum samples collected from 18 HIV-infected adult tuberculosis patients at regular intervals up to 84 days after treatment initiation. The first sputum was collected at home and brought to the clinic, where a second and third sputum were consecutively collected under supervision following mouthwash with bottled water and chlorhexidine solution respectively. All sputa were processed for liquid culture in duplicate.

RESULTS

Out of 556 cultures 430 (77.3%), 91 (16.4%) and 35 (6.3%) were positive, negative or contaminated, respectively. The odds of contamination were higher with home collection and with water rinse than with chlorhexidine rinse (OR: 12.5, p < 0.001 and OR: 6.7, p = 0.015). Chlorhexidine rinse increased the odds of a negative culture compared to water rinse (OR: 3.5, p = 0.002). The odds of a positive culture were greater with water rinse than with home collection (OR: 2.5, p = 0.005). Water rinse significantly reduced time to culture positivity.

CONCLUSION

Compared to sputum collected at home, chlorhexidine rinse reduces culture contamination and water rinse increases the rate and viable mycobacterial load of positive cultures.

Quantification of viable bacterial load in artificial sputum spiked with Mycobacterium tuberculosis

OBJECTIVE

Artificial sputum spiked with Mycobacterium tuberculosis could serve for validation of procedures that determine viable mycobacterial load.

DESIGN

Artificial sputum specimens prepared in-house were spiked with low, medium or high concentrations of Mycobacterium tuberculosis H37Rv stock solution. In a first series, a single technologist processed two batches of specimens daily with high load that were stored refrigerated or at room temperature for up to 8 days. In a second series, nine different technologists processed freshly made batches of specimens with low, medium or high loads. We recorded time to positivity (TTP) in duplicate liquid cultures made from each specimen.

RESULTS

Specimens were well grouped around the mean TTP (hours; standard deviation) of low: 271.7 (25.9), medium: 233.5 (16.3), and two batches of high load: 186.9 (12.3) and 191.8 (9.0), respectively. A variance component model that included load, storage temperature, days of storage until processing, batch of specimens made, sample ID and technologist ID as random effects in a linear mixed-effects model identified only load, technologist and residual as significant contributors to overall TTP variance.

CONCLUSION

Artificial sputum specimens with reproducible and stable viable mycobacterial loads can be made that could serve for training and validation purposes.

Propidium monoazide and Xpert MTB/RIF to quantify Mycobacterium tuberculosis cells

Propidium monoazide (PMA) penetrates non-viable cells with compromised membranes. PMA has been proposed to improve the specificity of Xpert MTB/RIF (Xpert) for the detection of viable Mycobacterium tuberculosis. This study assessed the effect of PMA on Xpert cycle thresholds (C_T) of M. tuberculosis made non-viable under antibiotic pressure. In vitro, we measured the difference between C_T with and without PMA (ΔC_T) in liquid cultures treated with one of six anti-tuberculosis drugs (isoniazid, rifampin, pyrazinamide, ethambutol, streptomycin, moxifloxacin) and found significant ΔC_T only with isoniazid and ethambutol for pan-susceptible M. tuberculosis and only with ethambutol for extensively drug-resistant M. tuberculosis. In the clinic we assessed ΔC_T in sputum samples collected from patients with pulmonary tuberculosis before and at regular intervals over 12 weeks after initiation of treatment. Before treatment start, estimated C_T were 19.3 (95% CI: 17.1-21.4) and 19.8 (95% CI: 17.6-22.1) without and with PMA, respectively. Under treatment C_T increased by 2.54 per √√day (95% CI: 1.38-3.69) without PMA and an additional 0.55 per √√day (95% CI: 0.37-0.74; p < 0.0001) with PMA. We conclude that PMA increases the specificity of Xpert for viable M. tuberculosis but the effect is small and dependent on the antibiotics used.

Improved diagnosis of childhood tuberculous meningitis using more than one nucleic acid amplification test

BACKGROUND

Early treatment is critical to reducing tuberculous meningitis (TBM) related morbidity and mortality. Diagnosis based on cerebrospinal fluid (CSF) culture is impractical due to slow turnaround times, while microscopy has poor sensitivity. Enhanced detection methods are essential to guide early treatment initiation, especially in vulnerable young children.

METHODS

We assessed the diagnostic accuracy of the GenoType(®) MTBDRplus and Xpert(®) MTB/RIF assays on CSF collected from paediatric meningitis suspects prospectively enrolled at Tygerberg Hospital, Cape Town, South Africa. Fluorescent auramine-O microscopy, liquid culture for Mycobacterium tuberculosis, GenoType and Xpert assays were performed on all CSF samples.

RESULTS

Of 101 meningitis suspects, 55 were diagnosed with TBM and 46 served as non-TBM controls. Using a pre-defined TBM case definition as reference standard, sensitivities and specificities were 4% and 100% for fluorescent microscopy, 22% and 100% for culture, 33% and 98% for GenoType, 26% and 100% for Xpert, 22% and 100% for microscopy and culture combined and 49% and 98% for GenoType and Xpert combined. Culture, GenoType and Xpert combined performed best, with 56% sensitivity and 98% specificity.

CONCLUSION

Although commercial nucleic-acid amplification tests performed on CSF revealed incrementally improved diagnostic accuracy, providing rapid microbiological confirmation, they cannot serve as a rule-out test.

Mycobactericidal activity of sutezolid (PNU-100480) in sputum (EBA) and blood (WBA) of patients with pulmonary tuberculosis

Rationale

Sutezolid (PNU-100480) is a linezolid analog with superior bactericidal activity against Mycobacterium tuberculosis in the hollow fiber, whole blood and mouse models. Like linezolid, it is unaffected by mutations conferring resistance to standard TB drugs. This study of sutezolid is its first in tuberculosis patients.

Methods

Sputum smear positive tuberculosis patients were randomly assigned to sutezolid 600 mg BID (N = 25) or 1200 mg QD (N = 25), or standard 4-drug therapy (N = 9) for the first 14 days of treatment. Effects on mycobacterial burden in sputum (early bactericidal activity or EBA) were monitored as colony counts on agar and time to positivity in automated liquid culture. Bactericidal activity was also measured in ex vivo whole blood cultures (whole blood bactericidal activity or WBA) inoculated with M. tuberculosis H37Rv.

Results

All patients completed assigned treatments and began subsequent standard TB treatment according to protocol. The 90% confidence intervals (CI) for bactericidal activity in sputum over the 14 day interval excluded zero for all treatments and both monitoring methods, as did those for cumulative WBA. There were no treatment-related serious adverse events, premature discontinuations, or dose reductions due to laboratory abnormalities. There was no effect on the QT interval. Seven sutezolid-treated patients (14%) had transient, asymptomatic ALT elevations to 173±34 U/L on day 14 that subsequently normalized promptly; none met Hy's criteria for serious liver injury.

Conclusions

The mycobactericidal activity of sutezolid 600 mg BID or 1200 mg QD was readily detected in sputum and blood. Both schedules were generally safe and well tolerated. Further studies of sutezolid in tuberculosis treatment are warranted.

Trial Registration

ClinicalTrials.gov NCT01225640

Early stationary phase culture supernatant accelerates growth of sputum cultures collected after initiation of anti-tuberculosis treatment

We investigated the effect of Mycobacterium tuberculosis culture supernatant added to sputum cultures collected during the first 8 weeks of anti-tuberculosis treatment. With ongoing treatment duration, time to culture positivity decreased significantly in supernatant-enriched cultures, possibly due to stimulation of dormant or slowly metabolizing M. tuberculosis cells.

Assessment of the sensitivity and specificity of Xpert MTB/RIF assay as an early sputum biomarker of response to tuberculosis treatment

BACKGROUND

An accurate biomarker is urgently needed to monitor the response to treatment in patients with pulmonary tuberculosis. The Xpert MTB/RIF assay is a commercially available real-time PCR that can be used to detect Mycobacterium-tuberculosis-specific DNA sequences in sputum samples. We therefore evaluated this assay with serial sputum samples obtained over 26 weeks from patients undergoing treatment for tuberculosis.

METHODS

We analysed sputum samples from 221 patients with smear-positive tuberculosis enrolled at two sites (Cape Town, South Africa, and Mbeya, Tanzania) of a multicentre randomised clinical trial REMoxTB of antituberculosis treatment on a weekly basis (weeks 0 to 8), then at weeks 12, 17, 22, and 26 after treatment initiation. The Xpert MTB/RIF results over time were compared with the results of standard smear microscopy and culture methods.

FINDINGS

We obtained and analysed 2741 sputum samples from 221 patients. The reduction in positivity rates with Xpert MTB/RIF were slower than those with the standard methods. At week 8, positive results were obtained for 62 (29%) of 212 sputum samples with smear microscopy, 46 (26%) of 175 with solid culture (Löwenstein-Jensen medium), 77 (42%) of 183 with liquid culture (Bactec MGIT960 system), and 174 (84%) of 207 with Xpert MTB/RIF; at 26 weeks, positive results were obtained for ten (5%) of 199, four (3%) of 157, seven (4%) of 169, and 22 (27%) of 83 sputum samples, respectively. The reduction in detection of quantitative M tuberculosis DNA with Xpert MTB/RIF correlated with smear grades (ρ=-0·74; p<0·0001), solid culture grades (ρ=-0·73; p<0·0001), and time to liquid culture positivity (ρ=0·73; p<0·0001). Compared with the combined binary smear and culture results as a reference standard, the Xpert MTB/RIF assay had high sensitivity (97·0%, 95% CI 95·8-97·9), but poor specificity (48·6%, 45·0-52·2).

INTERPRETATION

The poor specificity precludes the use of the Xpert MTB/RIF assay as a biomarker for monitoring tuberculosis treatment, and should not replace standard smear microscopy and culture.

FUNDING

Global Alliance for TB Drug Development, Bill & Melinda Gates Foundation, UK Medical Research Council, German Ministry of Science and Technology.

Adenosine triphosphate binding cassette (ABC) transporters are expressed and regulated during terminal keratinocyte differentiation: a potential role for ABCA7 in epidermal lipid reorganization

Central aspects of the cellular lipid trafficking mechanisms that occur during keratinocyte differentiation are still not well understood. In the past years, evidence has accumulated to suggest that members of the superfamily of adenosine triphosphate binding cassette (ABC) transporters are critically involved in the transmembrane transport of cellular lipids. To test the hypothesis that ABC molecules are potentially involved in the epidermal transport of sphingolipids, glycerophospholipids, cholesterol, and fatty acids, we performed mRNA expression profiling of all currently known ABC molecules during in vitro differentiation of human keratinocytes and HaCaT cells. We identified six ABC molecules that displayed significant regulation during differentiation of these cells. The recently cloned transporter ABCA7 was highly expressed in keratinocytes and HaCaT cells and upregulated during differentiation. Overexpression of ABCA7 in HeLa cells resulted in increased expression of intracellular and cell surface ceramide and elevated intracellular phosphatidylserine levels. Given the observation that during terminal keratinocyte differentiation intracellular and surface ceramide levels are increased, our results render ABCA7 a candidate regulator of ceramide transport in this process. In addition to ABCA7, the cholesterol transporters ABCB1 and ABCG1 and the glutathione/glucuronide sulfate transporters ABCC1, ABCC3, and ABCC4, were strongly upregulated during keratinocyte and HaCaT cell differentiation. These findings support the notion that ABCB1 and ABCG1 are potentially implicated in cholesterol transport, whereas ABCC1, ABCC3, and ABCC4 are candidate regulators of the translocation of sulfated lipids during stratum corneum keratinization. Our results suggest specific biologic functions for members of the ABC transporter family in epidermal lipid reorganization during terminal keratinocyte differentiation.

Lipoprotein (a) up-regulates the expression of the plasminogen activator inhibitor 2 in human blood monocytes

Elevated plasma lipoprotein (a) (Lp[a]) and cardiac events show a modest but significant association in various clinical studies. However, the influence of high Lp(a) on the gene expression in blood monocytes as a major cell involved in atherogenesis is poorly described. To identify genes influenced by elevated serum Lp(a), the gene expression was analyzed on a complementary DNA microarray comparing monocytes from a patient with isolated Lp(a) hyperlipidemia and coronary heart disease with monocytes from a healthy blood donor with low Lp(a). By using this approach, numerous genes were found differentially expressed in patient-versus-control monocytes. Verification of these candidates by Northern blot analysis or semiquantitative polymerase chain reaction in monocytes from additional patients with Lp(a) hyperlipidemia and healthy blood donors with elevated Lp(a) confirmed a significant induction of plasminogen activator inhibitor type 2 (PAI-2) messenger RNA (mRNA) in monocytes from male, but not from female, individuals with high Lp(a), indicating that this observation is gender specific. This led also to increased intracellular and secreted PAI-2 protein in monocytes from male probands with Lp(a) hyperlipidemia. Plasminogen activator inhibitor type 1 (PAI-1) mRNA was found suppressed only in the patients' monocytes and not in healthy probands with high Lp(a) levels. Purified Lp(a) induced PAI-2 mRNA and protein and reduced PAI-1 expression in monocytes isolated from various controls. The finding that PAI-2 is elevated in monocytes from male patients with isolated Lp(a) hyperlipidemia and male healthy probands with high Lp(a) and that purified Lp(a) up-regulates PAI-2 in control monocytes in vitro indicate a direct, but gender-specific, effect of Lp(a) for the induction of PAI-2 expression.