Validation and optimization of host immunological bio-signatures for a point-of-care test for TB disease

The development of a non-sputum-based, point-of-care diagnostic test for tuberculosis (TB) is a priority in the global effort to combat this disease, particularly in resource-constrained settings. Previous studies have identified host biomarker signatures which showed potential, but there is a need to validate and refine these for development as a test. We recruited 1,403 adults presenting with symptoms suggestive of pulmonary TB at primary healthcare clinics in six countries from West, East and Southern Africa. Of the study cohort, 326 were diagnosed with TB and 787 with other respiratory diseases, from whom we randomly selected 1005 participants. Using Luminex(R) technology, we measured the levels of 20 host biomarkers in serum samples which we used to evaluate the diagnostic accuracy of previously identified and novel bio-signatures. Our previously identified seven-marker bio-signature did not perform well (sensitivity: 89%, specificity: 60%). We also identified an optimal, two-marker bio-signature with a sensitivity of 94% and specificity of 69% in patients with no history of previous TB. This signature performed slightly better than C-reactive protein (CRP) alone. The cut-off value for a positive diagnosis differed for human immuno-deficiency virus (HIV)-positive and -negative individuals. Notably, we also found that no signature was able to diagnose TB adequately in patients with a prior history of the disease. We have identified a two-marker, pan-African bio-signature which is more robust than CRP alone and meets the World Health Organization (WHO) target product profile requirements for a triage test in both HIV-negative and HIV-positive individuals. This signature could be incorporated into a point-of-care device, greatly reducing the necessity for expensive confirmatory diagnostics and potentially reducing the number of cases currently lost to follow-up. It might also potentially be useful with individuals unable to provide sputum or with paucibacillary disease. We suggest that the performance of TB diagnostic signatures can be improved by incorporating the HIV-status of the patient. We further suggest that only patients who have never had TB be subjected to a triage test and that those with a history of previous TB be evaluated using more direct diagnostic techniques.Cancer Signaling networks and Molecular Therapeutic

Improving nutritional status of children with cystic fibrosis at Red Cross War Memorial Children's Hospital

Aim: To determine the nutritional status of children attending a cystic fibrosis clinic in a tertiary hospital in South Africa and compare it to previously reported 10-year rates. Methods: Weights and heights were measured of 69 (37 male and 32 female) children aged between 1 year and 18 years. Expected weight-for-age, expected height-for-age, expected weight-for-height and body mass index (BMI) were compared with international standards for underweight, stunting, wasting and BMI goal. Results: The nutritional status of the patients has improved over the last 10 years, most significantly for wasting, which decreased from 58.3% in 1996 to 15.9% in 2006 (95% confidence interval (CI), 1.315-14.09, P < 0.05). Fifty-two percent of the children were underweight in 2006, compared with 66.7% in 1996 (95% CI, 0.044-13.96, P < 0.05). Stunting was found in 31.9% of the current sample. Females over 15 years had expected weight-for-age 25.9% lower than those between 10 years and 15 years, while no difference was found between the male age groups. Female height-for-age was 7.06 percentage points greater than males between 10 years and 15 years (95% CI, 2.16-11.96, P < 0.01). Males between 10 years and 15 years had significantly lower BMIs than the corresponding female group. Coloured patients had significantly lower BMIs than white patients in all age groups. Conclusions: These children demonstrated continuing improvement in nutritional status, although deficits remain. The normalisation of mean weight-for-age and weight-for-height with far fewer wasted patients is encouraging. Interventions are needed in some areas to ensure that all children show progress. © 2011 Paediatrics and Child Health Division (Royal Australasian College of Physicians).Articl

The role of molecular epidemiology in low-income, high-burden countries

[No abstract available]Editoria

Activation of the subthalamic nucleus and pedunculopontine tegmentum: Does it affect dopamine levels in the Substantia nigra, Nucleus accumbens and striatum?

Parkinson's disease is a neurodegenerative disorder, of which the most prominent morphological feature is the progressive loss of dopaminergic nigrostriatal neurons. Increased glutamatergic transmission in the basal ganglia has been implicated in the pathophysiology of Parkinson's disease (PD). This study investigated whether death of substantia nigra (SN) dopaminergic neurons could be caused by the hyperactivity of afferent pathways resulting in the release of a toxic dose of excitatory amino acids in the SN. Twice-daily unilateral stimulation of the subthalamic nucleus (STN) for 21 days, using two different pulse frequencies and current strengths, significantly increased amphetamine-induced rotation, whereas sham stimulated rats showed significantly reduced rotation. Striatal and SN dopamine (DA) levels were unaffected when compared to naive and sham stimulated rats. However, levels of the DA metabolite, homovanillic acid (HVA), were significantly higher in the ipsilateral anterior striata of rats that had been stimulated at high frequency (100 Hz) and low current (100 μA) as compared to sham treated animals. Stimulation of the pedunculopontine tegmentum (PPT), using a single kainic acid injection, did not affect DA concentration in the ipsilateral striatum and nucleus accumbens when compared to sham-treated rats. DA levels in the contralateral striatum and nucleus accumbens of lesioned rats were significantly higher than ipsilateral levels. DOPAC/DA ratios were lower in the contralateral striatum and nucleus accumbens, suggesting decreased DA turnover. Glutamic acid decarboxylase activity was significantly higher in the ipsilateral than the contralateral SN. The physical manifestations of PD require a large reduction in caudate and putamen DA levels and no such depletion was measured in this study. These results, therefore, do not support the hypothesis that Parkinson's disease may result from an overstimulation of substantia nigral DA neurons by glutamate afferents originating from the STN or PPT.Parkinson's disease is a neurodegenerative disorder, of which the most prominent morphological feature is the progressive loss of dopaminergic nigrostriatal neurons. Increased glutamatergic transmission in the basal ganglia has been implicated in the pathophysiology of Parkinson's disease (PD). This study investigated whether death of substantia nigra (SN) dopaminergic neurons could be caused by the hyperactivity of afferent pathways resulting in the release of a toxic dose of excitatory amino acids in the SN. Twice-daily unilateral stimulation of the subthalamic nucleus (STN) for 21 days, using two different pulse frequencies and current strengths, significantly increased amphetamine-induced rotation, whereas sham stimulated rats showed significantly reduced rotation. Striatal and SN dopamine (DA) levels were unaffected when compared to naive and sham stimulated rats. However, levels of the DA metabolite, homovanillic acid (HVA), were significantly higher in the ipsilateral anterior striata of rats that had been stimulated at high frequency (100 Hz) and low current (100 μA) as compared to sham treated animals. Stimulation of the pedunculopontine tegmentum (PPT), using a single kainic acid injection, did not affect DA concentration in the ipsilateral striatum and nucleus accumbens when compared to sham-treated rats. DA levels in the contralateral striatum and nucleus accumbens of lesioned rats were significantly higher than ipsilateral levels. DOPAC/DA ratios were lower in the contralateral striatum and nucleus accumbens, suggesting decreased DA turnover. Glutamic acid decarboxylase activity was significantly higher in the ipsilateral than the contralateral SN. The physical manifestations of PD require a large reduction in caudate and putamen DA levels and no such depletion was measured in this study. These results, therefore, do not support the hypothesis that Parkinson's disease may result from an overstimulation of substantia nigral DA neurons by glutamate afferents originating from the STN or PPT.ArticleArticl

Calculation of the stability of the IS6110 banding pattern in patients with persistent Mycobacterium tuberculosis disease

The interpretation of molecular epidemiologic data of Mycobacterium tuberculosis infection is dependent on the understanding of the stability and evolutionary characteristics of the DNA fingerprinting marker used to classify clinical isolates. This study investigated the stability of the IS6110 banding pattern in serial tuberculosis isolates collected from patients resident in an area with a high incidence of tuberculosis. Evolutionary changes were observed in 4% of the strains, and a half-life (t1/2) of 8.74 years was calculated, assuming a constant rate of change over time. This rate may be composed of a high rate of change seen during the early disease phase (t1/2 = 0.57 years) and a low rate of change seen in the late disease phase (t1/2 = 10.69 years). The early rate probably reflects change occurring during active growth prior to therapy, while the low late rate may reflect change occurring during or after treatment. We demonstrate that the calculation of these rates is strongly influenced by the time interval between onset of disease and sputum sampling. These calculations are further complicated by partial replacement of the original strain population, resulting in the sporadic appearance of clonal variants in sputum specimens. Therefore, the true extent of genetic diversity may be underestimated within each host, thereby influencing molecular epidemiological data used to establish transmission chains.Articl

Historic and recent events contribute to the disease dynamics of Beijing-like Mycobacterium tuberculosis isolates in a high incidence region

SETTING: A retrospective study in an urban setting with a high tuberculosis incidence. OBJECTIVE: To study the molecular epidemiology and disease dynamics of a prevalent Mycobacterium tuberculosis strain family, F29, a subset of the Beijing strains. DESIGN: Multi-locus DNA fingerprinting and genomic analysis was used to characterise F29 isolates. Demographic and molecular epidemiologic data were correlated with those of other isolates from the setting. The geographic locations of five F29 strain clusters were plotted using a geographic information system (GIS) and an index for geographic distribution was calculated. Their cumulative temporal occurrence was also plotted. RESULTS: The genomic similarity of F29 to the Beijingstrains was confirmed. A high degree of clustering predicted high disease transmission. Spatial distribution was mostly widespread except for one cluster. Smaller foci of transmission were observed. The temporal spread showed ongoing transmission. CONCLUSION: F29 belongs to the Beijing strain group. The prevalence and high degree of strain clustering, with limited geographic clustering, indicates that F29 strains are endemic in the study community. However, recent epidemiologic events also contributed to the disease spread. The combination of molecular epidemiologic, spatial and temporal data has enhanced our understanding of the disease dynamics of Beijing strains in our study community.Articl

Sequence polymorphism in the rrs gene of Mycobacterium tuberculosis is deeply rooted within an evolutionary clade and is not associated with streptomycin resistance

A mutation (C-to-T transition) at position 491 of the rrs gene was identified in a Mycobacterium tuberculosis strain family (n = 208 isolates) that was predominant in a suburb of Cape Town, South Africa. This nucleotide change is not involved in streptomycin resistance, and we suggest caution in assuming that all mutations in genes targeted by antituberculosis drugs confer drug resistance.Articl

Use of spoligotyping for accurate classification of recurrent tuberculosis

The spoligotyping method has become an important tool for the tracking of Mycobacterium tuberculosis strains in different epidemiological settings. In this study, we demonstrate the ability of the spoligotyping technique to accurately determine the pathogenetic mechanism of recurrent disease. This methodology has advantages over conventional restriction fragment length polymorphism methods which may be useful in large-scale intervention studies.Articl

Designation of Major Mycobacterial Interspersed Repetitive-Unit Types within Mycobacterium tuberculosis Beijing Genotype, an Important Point

[No abstract available]Lette

Proportion of tuberculosis transmission that takes place in households in a high-incidence area

The prevalence of infection among household contacts of people with tuberculosis is high. This information frequently guides active case finding. We analysed DNA fingerprints of Mycobacterium tuberculosis from 765 tuberculosis patients in Ravensmead and Uitsig, adjacent suburbs of Cape Town, South Africa. In 129 households in which DNA fingerprints were available for more than one patient, we identified 313 patients, of whom 145 (46%) had a fingerprint pattern matching that of another member of the household. The proportion of transmission in the community that took place in the household was 19%, and therefore, in this high-incidence area, tuberculosis transmission occurs mainly outside the household.Articl