Tania Thomas

Malnutrition and helminth infection affect performance of an interferon γ-release assay.

OBJECTIVE: We sought to compare the tuberculin skin test (TST) to the QuantiFERON-TB Gold In-Tube assay (QFT-IT) and assess the effects of malnourishment and intestinal helminth infection on QFT-IT results. METHODS: In this population-based cross-sectional study from Dhaka, Bangladesh, we screened children for latent tuberculosis infection with the QFT-IT and TST. We assess the agreement between the TST and QFT-IT, risk factors associated with indeterminate QFT-IT results, and magnitude of interferon γ (IFN-γ) production. RESULTS: Three hundred and two children (aged 11–15.3 years) were enrolled, including 93 (30.8%) who were malnourished. Of 251 participants who provided stool samples, 117 (46.6%) were infected with Ascaris lumbricoides and/or Trichuris trichiura. TST results were positive (≥10 mm) for 101 (33.4%) children and negative for 201 (66.6%) children. QFT-IT results were positive for 107 (35.4%) children, negative for 121 (40.1%) children, and indeterminate for 74 (24.5%) children. Agreement between the tests was moderate (κ = 0.55 [95% confidence interval: 0.44–0.65]; P < .0001) when excluding indeterminate results. Children with indeterminate QFT-IT results were separately compared with children with positive and negative QFT-IT results; malnutrition (P = .0006 and .0003), and helminth infection (P = .05 and .02), and the statistical interaction between these 2 terms (P = .03 and .004) were associated with indeterminate results. Higher levels of IFN-γ in response to tuberculosis antigens were associated with positive TST results (P < .0001); lower levels were associated with malnutrition (P = .02). CONCLUSIONS: Malnutrition and helminth infections were associated with indeterminate QFT-IT results. Therefore, the presence of such conditions may limit the interpretability of QFT-IT results in children.

18-fluorodeoxyglucose positron emission tomography for tuberculosis diagnosis and management: a case series

BackgroundF-fluorodeoxyglucose positron emission tomography (FDG-PET) is increasingly used to investigate for malignancy in the evaluation of pulmonary nodules, yet both active tuberculosis (TB) and malignancy have high uptake of FDG. Definitive diagnosis of TB can be further hindered in patients without growth of the organism from sputum.Case presentationsWe describe a series of four representative cases of TB in varying disease state originally imaged by FDG-PET during evaluation for malignancy. Decisions regarding treatment for active TB in the presence of negative cultures and the evolving understanding of the spectrum of the TB disease state are discussed.ConclusionsFDG-PET may possess a role in the diagnosis of active TB infection in settings where conventional microbiological methods are unavaiable and holds particular promise for monitoring response to therapy in cases of unsettled treatment duration such as multidrug-resistant TB or in extrapulmonary TB.

Blood cultures for the diagnosis of multidrug-resistant and extensively drug-resistant tuberculosis among HIV-infected patients from rural South Africa: a cross-sectional study.

BackgroundThe yield of mycobacterial blood cultures for multidrug-resistant (MDR) and extensively drug-resistant tuberculosis (XDR-TB) among drug-resistant TB suspects has not been described.MethodsWe performed a retrospective, cross-sectional analysis to determine the yield of mycobacterial blood cultures for MDR-TB and XDR-TB among patients suspected of drug-resistant TB from rural South Africa. Secondary outcomes included risk factors of Mycobacterium tuberculosis bacteremia and the additive yield of mycobacterial blood cultures compared to sputum culture.ResultsFrom 9/1/2006 to 12/31/2008, 130 patients suspected of drug-resistant TB were evaluated with mycobacterial blood culture. Each patient had a single mycobacterial blood culture with 41 (32%) positive for M. tuberculosis, of which 20 (49%) were XDR-TB and 8 (20%) were MDR-TB. One hundred fourteen (88%) patients were known to be HIV-infected. Patients on antiretroviral therapy were significantly less likely to have a positive blood culture for M. tuberculosis (p = 0.002). The diagnosis of MDR or XDR-TB was made by blood culture alone in 12 patients.ConclusionsMycobacterial blood cultures provided an additive yield for diagnosis of drug-resistant TB in patients with HIV from rural South Africa. The use of mycobacterial blood cultures should be considered in all patients suspected of drug-resistant TB in similar settings.

Prevalence of methicillin-resistant Staphylococcus aureus nasal carriage among hospitalised patients with tuberculosis in rural Kwazulu-Natal.

BACKGROUND There is little information regarding the presence and characteristics of methicillin-resistant Staphylococcus aureus (MRSA), an important nosocomial pathogen, in rural African hospitals. OBJECTIVES To determine the prevalence of MRSA colonisation in patients admitted to a rural hospital with tuberculosis (TB) in an endemic HIV area and to describe transmission dynamics and resistance patterns among MRSA isolates. METHODS A prospective prevalence survey in the adult TB wards of the Church of Scotland Hospital, a provincial government district hospital in Tugela Ferry, KwaZulu-Natal. Patients were eligible if over the age of 15 and admitted to the TB wards between 15 November and 15 December 2008. Nasal swabs were cultured within 24 hours of admission and repeated at hospital-day 14 or upon discharge. Susceptibility testing was performed with standard disk diffusion. Demographic and clinical information was extracted from medical charts. RESULTS Of 52 patients with an admission nasal swab, 11 (21%) were positive for MRSA. An additional 4 (10%) of patients with negative admission swabs were positive for MRSA on repeat testing. MRSA carriage on admission was more common among patients with previous hospitalisation, and among HIV-infected patients was significantly associated with lower CD4 counts (p = 0.03). All MRSA isolates were resistant to cotrimoxazole, and 74% were resistant to > 5 dclasses of antibiotics; all retained susceptibility to vancomycin. CONCLUSIONS A high prevalence of multidrug-resistant MRSA nasal carriage was found. Studies are needed to validate nosocomial acquisition and to evaluate the impact of MRSA on morbidity and mortality among TB patients in similar settings.

A new potential biomarker for childhood tuberculosis

One of the major research areas for tuberculosis (TB) focuses not only on diagnostics but also on biomarkers that can provide prognostic data about the disease course and response to treatment. Although progress has been made, improved tests for paediatric TB are especially needed. Young children are at increased risk of progressing to TB after exposure, and may suffer from disseminated forms of the disease. Due to the paucibacillary nature of paediatric disease, the current armamentarium and future pipeline of TB diagnostics that largely rely on microbial growth and/or molecular detection are unlikely to demonstrate performance equivalent to that in adults. Thus, an accurate surrogate marker of disease may be crucial to improving the diagnosis of paediatric TB. We have tested and evaluated a novel B-cell assay called the antibodies in lymphocyte supernatant, or ALS, which has performed very well in diagnosing TB disease both in Asia1 2 and Africa (manuscript in preparation). Here, we report the performance of ALS as a biomarker in children with culture-confirmed TB. The ALS assay is based on a principle similar to that of the enzyme-linked immunosorbent spot assay, measuring antibody-secreting cells in cultures of peripheral blood mononuclear cells (PBMCs). The ALS assay detects antibody secretion from in vivo activated plasma B …

A Combination Regimen Design Program Based on Pharmacodynamic Target Setting for Childhood Tuberculosis: Design Rules for the Playground

Children with tuberculosis are treated with drug regimens copied from adults despite significant differences in antibiotic pharmacokinetics, pathology, and the microbial burden between childhood and adult tuberculosis. We sought to develop a new and effective oral treatment regimen specific to children of different ages. We investigated and validated the concept that target drug concentrations associated with therapy failure and death in children are different from those of adults. On that basis, we proposed a 4-step program to rapidly develop treatment regimens for children. First, target drug concentrations for optimal efficacy are derived from preclinical models of disseminated tuberculosis that recapitulate pediatric pharmacokinetics, starting with monotherapy. Second, 2-drug combinations were examined for zones of synergy, antagonism, and additivity based on a whole exposure–response surface. Exposures associated with additivity or synergy were then combined and the regimen was compared to standard therapy. Third, several exposures of the third drug were added, and a 3-drug regimen was identified based on kill slopes in comparison to standard therapy. Fourth, computer-aided clinical trial simulations are used to identify clinical doses that achieve these kill rates in children in different age groups. The proposed program led to the development of a 3-drug combination regimen for children from scratch, independent of adult regimens, in <2 years. The regimens and doses can be tested in animal models and in clinical trials.

Outbreak of pyrazinamide-monoresistant tuberculosis identified using genotype cluster and social media analysis.

SETTING Monoresistance to pyrazinamide (PZA) has infrequently been associated with Mycobacterium tuberculosis. OBJECTIVE To report an outbreak of PZA-monoresistant M. tuberculosis in Virginia involving two genotype clusters from December 2004 to August 2010. RESULTS Thirty cases were identified involving a predominantly young, US-born population with histories of substance use and incarceration and a large proportion of children aged <15 years (n= 6, 20%); of these, 23 cases (77%) were culture-confirmed as M. tuberculosis complex. DNA fingerprinting and molecular analysis of the PZA resistance gene, pncA, demonstrated a clonal strain that was not M. bovis. Genotypic data provided the initial link between seemingly unrelated cases, and helped reveal a historic genotype cluster of cases from 2004. Further genotype cluster and contact investigation procedures, including the novel use of the social networking website Facebook.com, revealed additional links between the 2004 and 2009 genotype clusters and described an ongoing, extensive outbreak necessitating an enhanced screening and treatment protocol for contacts. CONCLUSIONS This outbreak demonstrates how tuberculosis can spread through a young, vulnerable population. The use of genotypic data and the novel incorporation of social media investigations were critical to understanding the settings and context of infectivity.

Evaluation of the Antibody in Lymphocyte Supernatant Assay to Detect Active Tuberculosis

Background We aimed to evaluate the antibody in lymphocyte supernatant (ALS) assay as a biomarker to diagnose tuberculosis among adults from Tanzania with and without HIV. Methods Adults admitted with suspicion for tuberculosis had sputa obtained for GeneXpert MTB/RIF, acid-fast bacilli smear and mycobacterial culture; blood was obtained prior to treatment initiation and after 4 weeks. Adults hospitalized with non-infectious conditions served as controls. Peripheral blood mononuclear cells were cultured unstimulated for 72 hours. Anti-mycobacterial antibodies were measured from culture supernatants by ELISA, using BCG vaccine as the coating antigen. Median ALS responses were compared between cases and controls at baseline and between cases over time. Results Of 97 TB cases, 85 were microbiologically confirmed and 12 were clinically diagnosed. Median ALS responses from TB cases (0.366 OD from confirmed cases and 0.285 from clinical cases) were higher compared to controls (0.085, p<0.001). ALS responses did not differ based on HIV status, CD4 count or sputum smear status. Over time, the median ALS values declined significantly (0.357 at baseline; 0.198 after 4-weeks, p<0.001). Conclusions Robust ALS responses were mounted by patients with TB regardless of HIV status, CD4 count, or low sputum bacillary burden, potentially conferring a unique niche for this immunologic biomarker for TB.