Immunogenicity of antigens from the TbD1 region present in M. africanum and missing from "modern" M. tuberculosis: a cross- sectional study

<p>Abstract</p> <p>Background</p> <p>Currently available tools cannot be used to distinguish between sub-species of the <it>M. tuberculosis </it>complex causing latent tuberculosis (TB) infection. <it>M. africanum </it>causes up to half of TB in West- Africa and its relatively lower progression to disease suggests the presence of a large reservoir of latent infection relative to <it>M. tuberculosis</it>.</p> <p>Methods</p> <p>We assessed the immunogenicity of the TbD1 region, present in <it>M. africanum </it>and absent from "modern" <it>M. tuberculosis</it>, in an ELISPOT assay using cells from confirmed <it>M. africanum </it>or <it>M. tuberculosis </it>infected TB patients without HIV infection in the Gambia.</p> <p>Results</p> <p>Antigens from the TbD1 region induced IFNγ responses in only 35% patients and did not discriminate between patients infected with <it>M. africanum </it>vs. <it>M. tuberculosis</it>, while PPD induced universally high responses.</p> <p>Conclusions</p> <p>Further studies will need to assess other antigens unique to <it>M. africanum </it>that may induce discriminatory immune responses.</p

Performance comparison of a pair of Lowenstein–Jensen media supplemented with pyruvate or glycerol, and the combination of both supplements in a single Lowenstein–Jensen medium for the growth support of the Mycobacterium tuberculosis complex

Objective/Background: To evaluate the performance of Lowenstein–Jensen medium (LJ) supplemented with pyruvate and glycerol (LJPG), compared with LJ supplemented with pyruvate (LJP) or glycerol (LJG) for the support of mycobacterial growth. Method: This study used 100 Ziehl-Neelsen-confirmed positive mycobacterium growth indicator tube 960 culture samples that were obtained from clinical samples during routine diagnosis. All cultures were inoculated in parallel on LJG/LJP and on LJGP, which were incubated and read weekly for the evidence of growth. The mycobacterial recovery rate, contamination rate, and time to detection were compared. Result: The recovery rate for LJG/LJP and for LJPG was 90% (90 samples) and 88% (88 samples), respectively (kappa p-value, 0.9). There was no significant difference in the contamination rate, which was 8% (8 samples) for LJG/LJP and 9% (9 samples) for LJPG. Mycobacterial growth was faster in LJPG (1.6 weeks) than in LJG/LJP (2 weeks). Conclusion: A single LJPG slope was not significantly different, compared with the usual pair of LJG or LJP slopes. This is a promising new culturing approach that could be used in Mycobacterium africanum-endemic in West African countries. It significantly reduces labor time and consumable costs and more quickly detects the M. tuberculosis complex

Large-scale evaluation of enzyme-linked immunospot assay and skin test for diagnosis of Mycobacterium tuberculosis infection against a gradient of exposure in The Gambia.

The purified protein derivative (PPD) skin test for Mycobacterium tuberculosis infection lacks specificity. We assessed 2 more specific M. tuberculosis antigens (ESAT-6 and CFP-10) by enzyme-linked immunospot assay (ELISPOT) compared with PPD by ELISPOT and skin test in The Gambia. Of 735 household contacts of 130 sputum smear-positive tuberculosis cases, 476 (65%) tested positive by PPD ELISPOT, 300 (41%) tested positive by PPD skin test, and 218 (30%) tested positive by ESAT-6/CFP-10 ELISPOT. Only 15 (2%) had positive ESAT-6/CFP-10 results and negative PPD results by ELISPOT. With increasing M. tuberculosis exposure, the percentage of subjects who were PPD skin test positive/ESAT-6/CFP-10 ELISPOT negative increased (P<.001), whereas the percentage of subjects who were PPD skin test negative/PPD ELISPOT positive decreased (P=.011). Eighteen (31%) ESAT-6/CFP-10 ELISPOT-positive subjects in the lowest exposure category had negative PPD skin test results. ESAT-6/CFP-10 ELISPOT probably offers increased specificity in the diagnosis of M. tuberculosis infection in this tropical setting of endemicity, at the cost of some sensitivity