Non-exponential growth of Mycobacterium leprae Thai-53 strain cultured in vitro.

In this study, attempts were made to culture this bacterium in media supplemented with a variety of biological materials to determine why cultivation of Mycobacterium leprae in vitro has not this far been successful. A slight increase in the number of cells in medium supplemented with human blood plasma and an extract of nude mouse tissue as observed after more than 3 months of cultivation at 30 °C. To ascertain whether this increase was real growth, the growth was analyzed by droplet digital PCR, which showed a slow increase in the copy number of cell-associated DNA and the release of a large amount of DNA into the culture medium from bacterial cells during cultivation. These results were supported by electron microscopic examination of M. leprae in infected mouse tissues, which showed that most of the replicated bacteria had degenerated and only a few cells survived. Based on these results, it was postulated that many of the replicated cells degenerate during M. leprae growth and that only a few cells remain to participate in the next growth stage. This means that, unlike other cultivable bacteria, the growth of M. leprae is not exponential and the number of cells therefore increase extremely slowly. Thus, accurate judging of the success of M. leprae cultivation requires observation of growth over a long period of time and careful measurement of the increase in number of viable cells.

QuantiFERON TB Gold: a new method for latent tuberculosis infection.

QuantiFERON-TB Gold obtained approval in 2003 by the Food and Drug Administration as a valid tool for the diagnosis of latent tuberculosis. In this report, we evaluated its potential use in the immunological diagnosis of Mycobacterium tuberculosis infections in different groups of subjects. Our data indicate that QuantiFERON-TB Gold is specific for identifying subjects who have come into contact with M. tuberculosis and its use alongside traditional diagnostic techniques may be an important instrument for controlling tuberculosis.

Anticardiolipin antibodies and dependence of a serum cofactor. A mechanism of thrombosis.

OBJECTIVE: To evaluate the dependence on the serum cofactor of anticardiolipin antibodies (aCL) in infectious and autoimmune diseases. We also studied their correlation with some clinical manifestations, specially thrombosis. METHODS: aCL were determined with a standard ELISA method, and a modified ELISA in which we substituted bovine serum albumin (BSA), gelatin and skim milk powder for fetal calf serum (FCS). Categorized variables were analyzed by means of the chi 2 test and Fisher's test. Four groups of patients were studied. Group 1. Patients with aCL and autoimmune disease (systemic lupus erythematosus [SLE] and the primary antiphospholipid syndrome [PAPS]). Group 2. Patients with aCL, no symptoms and no underlying infection or autoimmune disease. Group 3. Patients with aCL and infectious diseases (syphilis, leprosy, HIV infection and Q fever). Group 4. Control group. RESULTS: (a) 19 of 20 samples from patients in Group 1 disclosed cofactor dependence in aCL activity. (b) 17 of 19 samples from patients in Group 3 had aCL activity, that was independent of the presence of the cofactor. (c) 3 of 4 patients in Group 2 had cofactor independent aCL and one had cofactor dependent aCL activity. (d) no control group patient had aCL. (e) association of cofactor dependent aCL with the development of clinical manifestations (thrombosis) was statistically significant (p < 0.0001). (g) cofactor dependent aCL and cofactor independent aCL were, respectively, associated with autoimmune and infectious diseases (p < 0.0001). CONCLUSIONS: (a) Dependence or independence of the cofactor helps to differentiate "infectious" aCL from "autoimmune" aCL. (2) aCL related clinical manifestations (thrombosis) depends on the presence of cofactor dependent aCL and not on cofactor independent aCL.