Rapid detection of Mycobacterium tuberculosis biomarkers in a sandwich immunoassay format using a waveguide-based optical biosensor

Early diagnosis of active tuberculosis (TB) remains an elusive challenge, especially in individuals with disseminated TB and HIV co-infection. Recent studies have shown a promise for the direct detection of pathogen-specific biomarkers such as lipoarabinomannan (LAM) for the diagnosis of TB in HIV-positive individuals. Currently, traditional immunoassay platforms that suffer from poor sensitivity and high non-specific interactions are used for the detection of such biomarkers. In this manuscript, we demonstrate the development of sandwich immunoassays for the direct detection of three TB-specific biomarkers, namely LAM, early secretory antigenic target 6 (ESAT6) and antigen 85 complex (Ag85), using a waveguide-based optical biosensor platform. Combining detection within the evanescent field of a planar optical waveguide with functional surfaces that reduce non-specific interactions allows for the ultra-sensitive and quantitative detection of biomarkers (an order of magnitude enhanced sensitivity, as compared to plate-based ELISA) in complex patient samples (urine, serum) within a short time. We also demonstrate the detection of LAM in urine from a small sample of subjects being treated for TB using this approach with excellent sensitivity and 100% corroboration with disease status. These results suggest that pathogen-specific biomarkers can be applied for the rapid and effective diagnosis of disease. It is likely that detection of a combination of biomarkers offers greater reliability of diagnosis, rather than detection of any single pathogen biomarker. NCT00341601.

Pantoea agglomerans in immunodeficient patients with different respiratory symptoms

The aim of this paper was to determine in 32 patients from 4 different Mexican hospitals the frequency of opportunistic bacteria in the 2010 to 2011 time period. The patients were divided in 4 groups. Group 1 included 21 HIV positive patients with acute respiratory syndrome. Four HIV positive patients with tuberculosis symptoms were included in Group 2; two patients with tuberculosis symptoms and one asymptomatic person formed Group 3. Reference Group 4 included 4 patients from whom 4 strains of Mycobacterium spp. had been reported. The strains were isolated and identified by 16S rRNA gene amplification, API 20E and 50CH, biochemical test, and antibiotic sensitivity. The strains found were 10 Pantoea agglomerans, 6 Mycobacterium spp., 6 Pseudomonas spp. and 10 strains of normal floral species: Thermoactinomycetes bacterium (1), Enterococcus faecium (2), Bacillus licheniformis (1), Lactobacillus rhamnosus (2), Streptococcus oralis (2), Streptococcus anginosus (1), and Enterobacter hormaechei (1).