Growth on blood agar discriminates Mycobacterium avium and Mycobacterium intracellulare

Mycobacterium intracellulare and Mycobacterium avium (MAC) require specialized culture and identification procedures. To simplify the diagnosis, we inoculated reference strains, and 85 M. avium and 12 M. intracellulare clinical isolates, on egg-based and sheep blood agar. After 5 days of culture, there were significantly more colonies on sheep blood than on egg-based agar for M. avium (ratio: 250.5 ± 209) but not for M. intracellulare (ratio: 0.44 ±0.11). Using a ratio ≥20, the sensitivity of the identification of an MAC isolate as M. avium was 97.65%, the specificity was 100%, and the positive predictive value was 100%. Differential growth on egg-based and blood agar is an aid to the identification of MAC isolates

Sterilizing Activity of Second-Line Regimens Containing TMC207 in a Murine Model of Tuberculosis

The sterilizing activity of the regimen used to treat multidrug resistant tuberculosis (MDR TB) has not been studied in a mouse model. (TB) strain H37Rv, treated with second-line drug combinations with or without the diarylquinoline TMC207, and then followed without treatment for 3 more months to determine relapse rates (modified Cornell model).Bactericidal efficacy was assessed by quantitative lung colony-forming unit (CFU) counts. Sterilizing efficacy was assessed by measuring bacteriological relapse rates 3 months after the end of treatment.The relapse rate observed after 12 months treatment with the WHO recommended MDR TB regimen (amikacin, ethionamide, pyrazinamide and moxifloxacin) was equivalent to the relapse rate observed after 6 months treatment with the recommended drug susceptible TB regimen (rifampin, isoniazid and pyrazinamide). When TMC207 was added to this MDR TB regimen, the treatment duration needed to reach the same relapse rate dropped to 6 months. A similar relapse rate was also obtained with a 6-month completely oral regimen including TMC207, moxifloxacin and pyrazinamide but excluding both amikacin and ethionamide.In this murine model the duration of the WHO MDR TB treatment could be reduced to 12 months instead of the recommended 18–24 months. The inclusion of TMC207 in the WHO MDR TB treatment regimen has the potential to further shorten the treatment duration and at the same time to simplify treatment by eliminating the need to include an injectable aminoglycoside

T-cell and serological responses to Erp, an exported Mycobacterium tuberculosis protein, in tuberculosis patients and healthy individuals

<p>Abstract</p> <p>Background</p> <p>The identification of antigens able to differentiate tuberculosis (TB) disease from TB infection would be valuable. Cellular and humoral immune responses to Erp (Exported repetitive protein) – a recently identified <it>M. tuberculosis </it>protein – have not yet been investigated in humans and may contribute to this aim.</p> <p>Methods</p> <p>We analyzed the cellular and humoral immune responses to Erp, ESAT-6, Ag85B and PPD in TB patients, in BCG⁺individuals without infection, BCG⁺individuals with latent TB infection (LTBI) and BCG^-controls. We used lymphoproliferation, ELISpot IFN-γ, cytokine production assays and detection of specific human antibodies against recombinant <it>M. tuberculosis </it>proteins.</p> <p>Results</p> <p>We included 22 TB patients, 9 BCG⁺individuals without TB infection, 7 LTBI and 7 BCG^-controls. Erp-specific T cell counts were higher in LTBI than in the other groups. Erp-specific T cell counts were higher in LTBI subjects than TB patients (median positive frequency of 211 SFC/10⁶PBMC (range 118–2000) for LTBI subjects compared to 80 SFC/10⁶PBMC (range 50–191), p = 0.019); responses to PPD and ESAT-6 antigens did not differ between these groups. IFN-γ secretion after Erp stimulation differed between TB patients and LTBI subjects (p = 0.02). Moreover, LTBI subjects but not TB patients or healthy subjects produced IgG3 against Erp.</p> <p>Conclusion</p> <p>The frequencies of IFN-γ-producing specific T cells, the IFN-γ secretion and the production of IgG3 after Erp stimulation are higher in LTBI subjects than in TB patients, whereas PPD and ESAT-6 are not.</p

Antagonism between isoniazid and the combination pyrazinamide-rifampin against tuberculosis infection in mice.

Mice that had been inoculated intravenously with 6.30 log10 Mycobacterium tuberculosis H37Rv 14 days earlier were administered one of three combinations of drugs, i.e., isoniazid (INH)-rifampin (RMP)-pyrazinamide (PZA), INH-RMP, and RMP-PZA, during an initial 2-month period to mimic the initial phase of chemotherapy for human tuberculosis and during a later 4-month period to mimic the continuation phase of chemotherapy. At the end of the initial phase, all three combined regimens were found to have been highly effective in terms of the number of CFUs in the spleens of infected mice. The bactericidal activities of INH-RMP-PZA and INH-RMP were similar, whereas that of RMP-PZA was significantly greater. The spleens of all of the mice that had been treated initially with INH-RMP-PZA were culture negative by the end of 6 months of treatment, regardless of the regimen employed during the continuation phase. However, after an additional period of 6 months without treatment, the proportion of spleen culture positivity, or relapse rate, was significantly smaller in the subgroup treated with RMP-PZA during the continuation phase than in the subgroups treated with INH-RMP-PZA or INH-RMP; the relapse rate did not differ significantly between the latter two subgroups. These results suggest that antagonism occurs between INH and the combination RMP-PZA during both the initial and continuation phases of chemotherapy, compromising the benefit conferred by the addition of PZA to the combined regimen.The preliminary pharmacokinetic analysis suggested that the pharmacological interaction between INH and RMP was very likely to be involved in the mechanism of antagonism, as concomitant treatment with INH had significantly reduced the peak serum level and the area under the serum concentration-time curve of RMP in mice