Feasibility of the TBDx automated digital microscopy system for the diagnosis of pulmonary tuberculosis.

BACKGROUND: Improved and affordable diagnostic or triage tests are urgently needed at the microscopy centre level. Automated digital microscopy has the potential to overcome issues related to conventional microscopy, including training time requirement and inconsistencies in results interpretation. METHODS: For this blinded prospective study, sputum samples were collected from adults with presumptive pulmonary tuberculosis in Lima, Peru and Ho Chi Minh City, Vietnam. TBDx performance was evaluated as a stand-alone and as a triage test against conventional microscopy and Xpert, with culture as the reference standard. Xpert was used to confirm positive cases. FINDINGS: A total of 613 subjects were enrolled between October 2014 and March 2015, with 539 included in the final analysis. The sensitivity of TBDx was 62·2% (95% CI 56·6-67·4) and specificity was 90·7% (95% CI 85·9-94·2) compared to culture. The algorithm assessing TBDx as a triage test achieved a specificity of 100% while maintaining sensitivity. INTERPRETATION: While the diagnostic performance of TBDx did not reach the levels obtained by experienced microscopists in reference laboratories, it is conceivable that it would exceed the performance of less experienced microscopists. In the absence of highly sensitive and specific molecular tests at the microscopy centre level, TBDx in a triage-testing algorithm would optimize specificity and limit overall cost without compromising the number of patients receiving up-front drug susceptibility testing for rifampicin. However, the algorithm would miss over one third of patients compared to Xpert alone.

Identification of tuberculosis susceptibility genes with human macrophage gene expression profiles.

Although host genetics influences susceptibility to tuberculosis (TB), few genes determining disease outcome have been identified. We hypothesized that macrophages from individuals with different clinical manifestations of Mycobacterium tuberculosis (Mtb) infection would have distinct gene expression profiles and that polymorphisms in these genes may also be associated with susceptibility to TB. We measured gene expression levels of >38,500 genes from ex vivo Mtb-stimulated macrophages in 12 subjects with 3 clinical phenotypes: latent, pulmonary, and meningeal TB (n = 4 per group). After identifying differentially expressed genes, we confirmed these results in 34 additional subjects by real-time PCR. We also used a case-control study design to examine whether polymorphisms in differentially regulated genes were associated with susceptibility to these different clinical forms of TB. We compared gene expression profiles in Mtb-stimulated and unstimulated macrophages and identified 1,608 and 199 genes that were differentially expressed by >2- and >5-fold, respectively. In an independent sample set of 34 individuals and a subset of highly regulated genes, 90% of the microarray results were confirmed by RT-PCR, including expression levels of CCL1, which distinguished the 3 clinical groups. Furthermore, 6 single nucleotide polymorphisms (SNPs) in CCL1 were found to be associated with TB in a case-control genetic association study with 273 TB cases and 188 controls. To our knowledge, this is the first identification of CCL1 as a gene involved in host susceptibility to TB and the first study to combine microarray and DNA polymorphism studies to identify genes associated with TB susceptibility. These results suggest that genome-wide studies can provide an unbiased method to identify critical macrophage response genes that are associated with different clinical outcomes and that variation in innate immune response genes regulate susceptibility to TB.

The influence of HIV infection on clinical presentation, response to treatment, and outcome in adults with Tuberculous meningitis.

BACKGROUND: Tuberculous meningitis occurs more commonly in human immunodeficiency virus (HIV)-infected individuals than in HIV-uninfected individuals, but whether HIV infection alters the presentation and outcome of tuberculous meningitis is unknown. METHODS: We performed a prospective comparison of the presenting clinical features and response to treatment in 528 adults treated consecutively for tuberculous meningitis (96 were infected with HIV and 432 were uninfected with HIV) in 2 tertiary-care referral hospitals in Ho Chi Minh City, Vietnam. Logistic regression was used to model variables associated independently with HIV infection, 9-month survival, and the likelihood of having a relapse or an adverse drug event. Kaplan-Meier estimates were used to compare survival rates and times to fever clearance, coma clearance, relapse, and adverse events. RESULTS: HIV infection did not alter the neurological presentation of tuberculous meningitis, although additional extrapulmonary tuberculosis was more likely to occur in HIV-infected patients. The 9-month survival rate was significantly decreased in HIV-infected patients (relative risk of death from any cause, 2.91 [95% confidence interval, 2.14-3.96]; P < .001), although the times to fever clearance and coma clearance and the number or timing of relapses or adverse drug events were not significantly different between the groups. CONCLUSIONS: HIV infection does not alter the neurological features of tuberculous meningitis but significantly reduces the survival rate.

Transposition rates of Mycobacterium tuberculosis IS6110 restriction fragment length polymorphism patterns.

To determine the rate at which IS6110 restriction fragment length polymorphism (RFLP) patterns in Mycobacterium tuberculosis change over time, we applied a smooth nonparametric survival model to several data sets, including data from previous publications on the rate of change. The results strongly suggest a simple parametric model, with an instantaneous change at time zero and essentially a zero rate of change thereafter. Our interpretation of the results is that at the time of collection of the first isolate, more than one strain is present. We speculate that the selection of mutant strains is most likely during rapid growth, revival of the dormant bacteria, and/or adaptation to a new host. The parameter most accurately describing changing RFLP patterns is the proportion of isolates with band changes, rather than the half-life or the rate of change.