Acetic Acid Enables Molecular Enumeration of Mycobacterium tuberculosis from Sputum and Eliminates the Need for a Biosafety Level 3 Laboratory

BACKGROUND

Improved monitoring of Mycobacterium tuberculosis response to treatment is urgently required. We previously developed the molecular bacterial load assay (MBLA), but it is challenging to integrate into the clinical diagnostic laboratory due to a labor-intensive protocol required at biosafety level 3 (BSL-3). A modified assay was needed.

METHODS

The rapid enumeration and diagnostic for tuberculosis (READ-TB) assay was developed. Acetic acid was tested and compared to 4 M guanidine thiocyanate to be simultaneously bactericidal and preserve mycobacterial RNA. The extraction was based on silica column technology and incorporated low-cost reagents: 3 M sodium acetate and ethanol for the RNA extraction to replace phenol-chloroform. READ-TB was fully validated and compared directly to the MBLA using sputa collected from individuals with tuberculosis.

RESULTS

Acetic acid was bactericidal to M. tuberculosis with no significant loss in 16S rRNA or an unprotected mRNA fragment when sputum was stored in acetic acid at 25°C for 2 weeks or -20°C for 1 year. This novel use of acetic acid allows processing of sputum for READ-TB at biosafety level 2 (BSL-2) on sample receipt. READ-TB is semiautomated and rapid. READ-TB correlated with the MBLA when 85 human sputum samples were directly compared (R2 = 0.74).

CONCLUSIONS

READ-TB is an improved version of the MBLA and is available to be adopted by clinical microbiology laboratories as a tool for tuberculosis treatment monitoring. READ-TB will have a particular impact in low- and middle-income countries (LMICs) for laboratories with no BSL-3 laboratory and for clinical trials testing new combinations of anti-tuberculosis drugs.

Exhaled Mycobacterium tuberculosis Predicts Incident Infection in Household Contacts

BACKGROUND

Halting transmission of Mycobacterium tuberculosis (Mtb) by identifying infectious individuals early is key to eradicating tuberculosis (TB). Here we evaluate face mask sampling as a tool for stratifying the infection risk of individuals with pulmonary TB (PTB) to their household contacts.

METHODS

Forty-six sputum-positive PTB patients in The Gambia (August 2016-November 2017) consented to mask sampling prior to commencing treatment. Incident Mtb infection was defined in 181 of their 217 household contacts as QuantiFERON conversion or an increase in interferon-γ of ≥1 IU/mL, 6 months after index diagnosis. Multilevel mixed-effects logistical regression analysis with cluster adjustment by household was used to identify predictors of incident infection.

RESULTS

Mtb was detected in 91% of PTB mask samples with high variation in IS6110 copies (5.3 × 102 to 1.2 × 107). A high mask Mtb level (≥20 000 IS6110 copies) was observed in 45% of cases and was independently associated with increased likelihood of incident Mtb infection in contacts (adjusted odds ratio, 3.20 [95% confidence interval, 1.26-8.12]; P = .01), compared with cases having low-positive/negative mask Mtb levels. Mask Mtb level was a better predictor of incident Mtb infection than sputum bacillary load, chest radiographic characteristics, or sleeping proximity.

CONCLUSIONS

Mask sampling offers a sensitive and noninvasive tool to support the stratification of individuals who are most infectious in high-TB-burden settings. Our approach can provide better insight into community transmission in complex environments.

Vitamin D in Gambian children with discordant tuberculosis (TB) infection status despite matched TB exposure: a case control study

Using a matched case control design conducted at MRC Gambia in 2015, we measured vitamin D levels in pairs of asymptomatic children with discordant tuberculin skin test status despite the same sleeping proximity to the same adult TB index case. Median ages of groups (infected; 10.0 years, uninfected 8.8 years) were not significantly different (p = 0.13). Mean vitamin D levels were 2.05 ng/mL (95% CI - 0.288 to 4.38) higher in 24 highly TB-exposed uninfected children compared with 24 matched highly TB-exposed infected children (p = 0.08). The findings warrant further investigation in larger studies to understand the implications and significance. Conclusion: Vitamin D levels were higher in TB-uninfected children compared with TB-infected despite equal high exposure to a TB case.

Monitoring Anti-tuberculosis Treatment Response Using Analysis of Whole Blood Mycobacterium tuberculosis Specific T Cell Activation and Functional Markers

Background

Blood-based biomarkers have been proposed as an alternative to current sputum-based treatment monitoring methods in active tuberculosis (ATB). The aim of this study was to validate previously described phenotypic, activation, and cytokine markers of treatment response in a West African cohort.

Methods

Whole blood immune responses to Mycobacterium tuberculosis ESAT-6/CFP-10 (EC) and purified protein derivative (PPD) were measured in twenty adults at baseline and after 2 months of standard TB treatment. Patients were classified as fast or slow responders based on a negative or positive sputum culture result at 2 months, respectively. Cellular expression of activation markers (CD38, HLA-DR), memory markers (CD27), and functional intracellular cytokine and proliferation (IFN-γ, Ki-67, TNF-α) markers were measured using multi-color flow cytometry.

Results

There was a significant increase in the proportion of CD4⁺CD27⁺ cells expressing CD38 and HLA-DR following EC stimulation at 2 months compared to baseline (p = 0.0328 and p = 0.0400, respectively). Following PPD stimulation, slow treatment responders had a significantly higher proportion of CD8⁺CD27^–IFN-γ⁺ (p = 0.0105) and CD4⁺CD27⁺HLA-DR⁺CD38⁺ (p = 0.0077) T cells than fast responders at baseline. Receiver operating curve analysis of these subsets resulted in 80% sensitivity and 70 and 100% specificity, respectively (AUC of 0.82, p = 0.0156 and 0.84, p = 0.0102).

Conclusion

Our pilot data show reductions in expression of T cell activation markers were seen with treatment, but this was not associated with fast or slow sputum conversion at 2 months. However, baseline proportions of activated T cell subsets are potentially predictive of the subsequent speed of response to treatment.

Protection against mycobacterial infection: A case-control study of mycobacterial immune responses in pairs of Gambian children with discordant infection status despite matched TB exposure

BACKGROUND

Children are particularly susceptible to tuberculosis. However, most children exposed to Mycobacterium tuberculosis are able to control the pathogen without evidence of infection. Correlates of human protective immunity against tuberculosis infection are lacking, and their identification would aid vaccine design.

METHODS

We recruited pairs of asymptomatic children with discordant tuberculin skin test status but the same sleeping proximity to the same adult with sputum smear-positive tuberculosis in a matched case-control study in The Gambia. Participants were classified as either Highly TB-Exposed Uninfected or Highly TB-Exposed Infected children. Serial luminescence measurements using an in vitro functional auto-luminescent Bacillus Calmette-Guérin (BCG) whole blood assay quantified the dynamics of host control of mycobacterial growth. Assay supernatants were analysed with a multiplex cytokine assay to measure associated inflammatory responses.

FINDINGS

29 pairs of matched Highly TB-Exposed Uninfected and Highly TB-Exposed Infected children aged 5 to 15 years old were enroled. Samples from Highly TB-Exposed Uninfected children had higher levels of mycobacterial luminescence at 96 hours than Highly TB-Exposed Infected children. Highly TB-Exposed Uninfected children also produced less BCG-specific interferon-γ than Highly TB-Exposed Infected children at 24 hours and at 96 hours.

INTERPRETATION

Highly TB-Exposed Uninfected children showed less control of mycobacterial growth compared to Highly TB-Exposed Infected children in a functional assay, whilst cytokine responses mirrored infection status.

FUNDING

Clinical Research Training Fellowship funded under UK Medical Research Council/Department for International Development Concordat agreement and part of EDCTP2 programme supported by European Union (MR/K023446/1). Also MRC Program Grants (MR/K007602/1, MR/K011944/1, MC_UP_A900/1122).

PO 8414 EVALUATION OF MYCOBACTERIUM TUBERCULOSIS COMPLEX (MTBC) CULTURE METHODS IN MYCOBACTERIUM AFRICANUM-ENDEMIC REGION OF WEST AFRICA

Background

With the endemic Mycobacterium africanum (Maf), West African laboratories use glycerol and pyruvate in separate LJ cultures (LJG and LJP) for isolation of MTBC. The aim of this work is to evaluate if combining both glycerol and pyruvate in a single LJ medium (LJGP) will lead to comparable growth characteristics and time to detection in comparison to LJG, LJP and MGIT 960.

Method

Total of 118 smear-positive sputum samples were processed using 4% NaOH-NALC decontamination method. The decontaminated samples were inoculated parallel on LJG, LGP, MGIT 960 and LJGP. Positive cultures were confirmed using Ziehl-Neelsen staining method. MTBC identification was done using the Capilia TBNeo kit and spoligotyping used for speciation.

Results

The recovery rate for LJG, LJP, LJPG and MGIT was found to be 73.7% (87/118), 82.2% (96/118), 83.9% (99/118) and 93.2% (110/118) respectively. No significant agreement was observed between the LJPG and MGIT 960 with Kappa values of −0.105 (p-value=0.199). However, there was significant agreement between LJGP and LJG and LJP with Kappa value of 0736 (p-value<0.001) and 0.756 (p-value<0.001), respectively. There were 70 Euro-American, 34 Maf, 9 East-Asian, 2’Indo-Oceanic, 2 East-African-Indian and 1 M. Bovis. LJGP have better Maf recovery rate, 85.3% (29/34) in comparison to MGIT 960, 79.4% (27/34), LJP, 76.5% (26/34) and LJG, 61.8% (21/34). Seven of the 8 MGIT negatives that were LJPG positive were M. africanum and 1 M. bovis.

Conclusion

LJPG has a better detection rate and time to positivity compared to LJG and LJP and was shown to have a better Maf recovery than other LJ methods and MGIT 960. It is evident that LJGP is a promising culture tool for Maf-endemic West African countries that will not only increase MTBC recovery rate in combination with MGIT, but also leads to better detection of Maf.

An Auto-luminescent Fluorescent BCG Whole Blood Assay to Enable Evaluation of Paediatric Mycobacterial Responses Using Minimal Blood Volumes

Introduction: Understanding protective human immunity against mycobacteria is critical to developing and evaluating new vaccines against tuberculosis. Children are the most susceptible population to infection, disease, and death from tuberculosis, but also have the strongest evidence of BCG-inducible protection. Limited amounts of blood can be obtained for research purposes in paediatrics and therefore there is a need for high-yield, low-volume, human immunology assays. Methods: We transformed BCG Danish with plasmids encoding luciferase full operon derived from Photorhabdus luminescens together with Green Fluorescent Protein and antibiotic selection markers. We characterised the luminescent and fluorescent properties of this recombinant BCG strain (BCG-GFP-LuxFO) using a luminometer and flow cytometry and developed a paediatric whole blood in vitro infection model. Results: Luminescence of BCG-GFP-LuxFO correlated with optical density (Spearman Rank Correlation coefficient r = 0.985, p < 0.0001) and colony forming units (CFUs) in liquid culture medium (r = 0.971, p < 0.0001). Fluorescence of BCG-GFP-LuxFO in paediatric whole blood was confirmed by flow cytometry in granulocytes and monocytes 1 h following infection. Luminescence of BCG-GFP-LuxFO in whole blood corresponded with CFUs (r = 0.7123, p < 0.0001). Conclusion: The BCG-GFP-LuxFO assay requires 225 μL whole blood per sample, from which serial luminescence measurements can be obtained, together with biochemical analysis of supernatants and cellular assay applications using its fluorescent properties. This offers the opportunity to study human-mycobacterial interactions using multiple experimental modalities with only minimal blood volumes. It is therefore a valuable method for investigating paediatric immunity to tuberculosis.

[Enhancing the anthelminthic activity roots of Annona sengalensis]

INTRODUCTION

Annona senegalensis is a plant largely used in traditional medicine in Africa. The roots showed an antiparsitic activity. The purpose of this work is to determine through bioassay on Rhabditis pseudoelongata the activity of the roots of Annona senegalensis and characterise if any substances responsible for this activity.

MATERIAL AND METHODS

The vegetable material consists of roots of Annona senegalensis collected in Casamance at 1999. The tests of activity are carried out on Rhabditis pseudoelongata, stock L. Lamy, Institut Pasteur, Paris. Powder of roots (1070 g) was extracted with methanol. From this rough extract, we carried out two extractions with the dichloromethane of which one after passages in alkaline and acid medium. Various extracts were subjected to a chromatography on column of silica gel or from alumina gel; some compounds were isolated by high performance liquid chromatography . The identification of compounds was deed using spectrometric techniques (mass, Ultraviolet, Infrared) and nuclear magnetic resonance. The tests of activity related to three extracts and seven molecules isolated from the roots. The percentage of dead worm is determined after two hours of contact with demineralised water containing the sample to be tested.

RESULTS

The neutral extract chloromethylenic showed an important activity on Rhabditis pseudoelongata. Five acetogenines were insulated starting from this extract chloromethylenic (gigantetronenine, squamocine, glaucanisine, glaucanetine, goniothalamicine) and two alkaloids starting from the alkaline extract chloromethylenic (liriodenine and norolivéroline). The tests on Rhabditis pseudoelongata of these compounds showed an activity of the squamocine with a IC50 of 0.1 microg/ml and IC90 0.3 microg/ ml more powerful than that of the levamisole, reference substance (IC50 of 0.8 microg/ml and IC90 13 microg/ml).

CONCLUSION

The study of the biological activity of the roots of Annona senegalensis made it possible to determine the anthelminthic activity of the extract chloromethylenic from where the squamocine was isolated. The presence of this molecule could explain the anthelminthic activity of this plant.

[Heterogeneity of chloroquine resistant malaria in Senegal]

In order to evaluate the in vivo efficacy of chloroquine in the treatment of P. falciparum malaria, studies have been carried out in Richard-Toll, Fatick and Tambacounda, 3 areas where dynamics of transmission, population movements, as well as prophylactic and curative practises are different. Failure rates in treatment were 13% in site 1 (Richard-Toll) where medical pressure and population movements are high. In sites 2 and 3 (Fatick and Tambacounda), the failure rate was 3%. Even if medical pressure is lower in the latter site (Tambacounda), the higher transmission could be a factor in the spreading of resistance. A surveillance system and better use of chloroquine must be undertaken.

The effect of different treatment regimens on the epidemiology of seasonally transmitted Schistosoma haematobium infections in four villages in the Senegal River Basin, Senegal

This paper describes the present epidemiological situation of Schistosoma haematobium in 4 villages in the middle valley of the Senegal River Basin, in terms of level and intensity of infection, seasonality of transmission, and intermediate hosts, and the effect of different treatment schedules with praziquantel on the overall infection levels and re-infection rates. The longitudinal study involving 7 surveys was carried out between June 1995 and March 1997 in Diatar, Guia, Donaye and Niandane. The prevalence and intensity of infection remained low throughout the survey (< 55% and < 12 eggs/10 mL urine), and there were no systematic differences in the prevalence or intensity of infection between men and women. Before treatment, infections were highly aggregated in individuals and were concentrated in children (aged < 15 years) with 85% of the potential contamination; no individual aged > 24 years produced > 50 eggs/10 mL urine. Using WHO guidelines mass treatment was given to all Diatar and Guia villagers in December 1995, whereas in Donaye and Niandane only individuals positive for eggs were treated. Six weeks post-treatment cure rates in all villages were > 80%, with marked declines in levels of infection (< 20% and < 4.5 eggs/10 mL). By March 1997 infection levels in Donaye and Niandane had returned to pre-treatment levels, whereas in the 2 mass-treated villages (Diatar and Guia) infection levels were still markedly reduced compared to pre-treatment levels. Rates of conversion were very low between all surveys; however, there was an apparent high level of reversion (> 20%), due to the alternation of individuals apparently positive and negative between surveys. Water and infected snails were present from June to March. Therefore, owing to the high aggregation of infections in children, the low overall infection levels and the transmission period, it is suggested that in this area the best treatment schedule would be selective treatment of school-aged children in March/April, probably on an annual basis.

Morbidity induced by Schistosoma haematobium infections, as assessed by ultrasound before and after treatment with praziquantel, in a recently expanded focus (Senegal River basin)

Seven years after the completion of two dams in the Senegal River basin, 203 individuals from four villages around Podor in the middle valley, where Schistosoma haematobium infections were present, were examined in June 1995. In December 1995 a single dose of praziquantel (40 mg/kg) was given to each of these subjects, who were re-examined in April 1996. Clinical and parasitological signs of infection were investigated at both examinations, and ultrasonography was performed to check for lesions of the urinary tract induced by S. haematobium. As uninfected controls, 200 people from four villages where S. haematobium was absent were similarly examined, in November 1995. Prior to treatment, bladder irregularities were observed in 43% of the subjects from Podor but only 6% of the uninfected controls. The severity of the bladder lesions visible by ultrasonography was significantly associated with intensity of infection, despite the generally low levels of infection in the subjects mean = 13.1 eggs/10 ml urine). Four months after treatment, however, the frequency of bladder irregularities among the subjects (11%) was similar to that in the uninfected controls and intensities of infection and other clinical signs of disease had also significantly declined. The prevalence of haematuria, for example, fell from 35% pre-treatment to 10% post-treatment. The results indicate that the onset of S. haematobium morbidity can be relatively rapid even in areas with seasonal and low levels of transmission, and demonstrate that treatment to reduce morbidity in such areas is important and could be relatively simple and very effective.

Royal Society of Tropical Medicine and Hygiene meeting at Manson House, London, 18 May 1995. The epidemiology of human schistosomiasis in the Senegal river basin

Extensive water development has taken place in the north of Senegal over the last decade, resulting in a large increase in the amount of fresh water for irrigation. The objectives of the present study were to determine the prevalence and intensity of Schistosoma mansoni and S. haematobium in the Senegal river basin (SRB), and to ascertain the distribution of the snail species acting as intermediate hosts for both species of schistosomes. The schistosomiasis survey started in January 1994 and was completed in March 1995. Compared to studies before the construction of the Diama dam, there was a significant increase in both the prevalence and intensity of urinary and intestinal schistosomiasis in the human population in parts of the SRB. From the 9014 people who were registered from 180 villages and 4 towns (10 districts), 7750 were examined. S. mansoni was found in the lower valley (lower delta-Senegal river, lower delta-Lampsar river, upper delta, and diéré) but not in the middle valley. The mean prevalence ranged from 4.4% in the lower delta-Senegal River to 71.8% in the zone of Lac de Guiers, where prevalence and intensity of infection were higher on the eastern side of the lake (81.3% with a mean number of 2088 eggs/g of faeces) compared with the western side (50.3% with a mean 1111 eggs/g). S. haematobium was recorded throughout the area of study, ranging from a mean prevalence of 0.37% in diére (lower valley) to 41.5% in the lower valley (Lampsar river), where the mean egg count was 313/10 mL of urine. Physical and chemical changes to the environment have favoured the spread and increase in the populations of freshwater snails. The only snail involved in the transmission of S. mansoni was Biomphalaria pfeifferi. Five species of bulinid snails were present--Bulinus globosus, Bu. umbilicatus, Bu. senegalensis, Bu. forskalii and Bu. truncatus--but only the first 3 species were involved in the transmission of S. haematobium in the lower and middle valleys.