Importance of differentiating Mycobaterium bovis in tuberculous meningitis.

The aim of the article is to describe the principal findings among patients with M.tuberculosis and M. bovis CNS infection. Mycobacterium tuberculosis is one of the most common infectious agents that cause death and neurological sequelae around the world. Most of the complications of CNS TB can be attributed to a delay in the diagnosis. Unfortunately, there are no specific diagnostic tools to support an early diagnosis. Other prognostic factors different from delay in treatment have not been identified. Clinical, radiological and laboratory characteristics were analyzed retrospectively from the medical files of all the patients admitted with the diagnoses of tuberculosis. Of 215 patients admitted with systemic tuberculosis, 64 (30%) had a neurological infection. Positive cultures were found in 54 (84%) cases, 18 (33%) in the CSF and the rest in other fluids or tissues. Adenosin deaminase (ADA) enzyme determination was more sensitive than M. tuberculosis PCR in the CSF for supporting an early diagnosis. In addition to a later clinical stage and treatment lag, positive CSF cultures (P=0.001) and the presence of M. bovis (P=0.020) were prognostic factors for a worse outcome. Neither older age, the presence of tuberculomas versus meningeal enhancement, or HIV co-infection, was associated to a worse prognosis. The isolation of M. bovis subspecies was more common that previously reported, and it was associated to the development of parenchymal lesions (P=0.032) when compared to M. tuberculosis. In this study, positive CSF cultures for M. tuberculosis and further identifying M. bovis species were additional prognostic factors for worse outcome. Positive cultures in systemic fluids other than CSF, even when the patient had no obvious systemic manifestations, and ADA determination in the CSF were noteworthy diagnostic tools for the diagnosis.

Unique gene expression profiles in infants vaccinated with different strains of Mycobacterium bovis bacille Calmette-Guerin.

Vaccination with Mycobacterium bovis bacille Calmette-Guérin (BCG) has variable efficacy in preventing tuberculosis. We hypothesized that some of this variation might be due to differences among BCG strains. To test this, neonates in Orizaba, Mexico, were vaccinated with one of three different BCG strains (BCG-Brazil [BBCG], BCG-Denmark [DBCG], or BCG-Japan [JBCG]). One year after vaccination, peripheral blood mononuclear cells (PBMC) were obtained and recall immune responses to culture filtrate proteins (CFP) of Mycobacterium tuberculosis were evaluated using quantitative real-time PCR. CFP-activated PBMC from BBCG- and DBCG-immunized children expressed high levels of cytokines characteristic of an adaptive immune response (gamma interferon, interleukin-2beta [IL-12beta], and IL-27), while those from children immunized with JBCG did not. In contrast, vaccination with JBCG resulted in significantly greater expression of cytokines characteristic of a proinflammatory immune response (IL-1alpha, IL-1beta, IL-6, and IL-24) in PBMC activated with CFP compared to PBMC from children vaccinated with BBCG or DBCG. Thus, different strains of BCG can activate different immune pathways, which may affect long-term vaccine efficacy.

Rapid detection of rifampin resistance in Mycobacterium tuberculosis isolates from India and Mexico by a molecular beacon assay.

We assessed the performance of a rapid, single-well, real-time PCR assay for the detection of rifampin-resistant Mycobacterium tuberculosis by using clinical isolates from north India and Mexico, regions with a high incidence of tuberculosis. The assay uses five differently colored molecular beacons to determine if a short region of the M. tuberculosis rpoB gene contains mutations that predict rifampin resistance in most isolates. Until now, the assay had not been sufficiently tested on samples from countries with a high incidence of tuberculosis. In the present study, the assay detected mutations in 16 out of 16 rifampin-resistant isolates from north India (100%) and in 55 of 64 rifampin-resistant isolates from Mexico (86%) compared to results with standard susceptibility testing. The assay did not detect mutations (a finding predictive of rifampin susceptibility) in 37 out of 37 rifampin-susceptible isolates from India (100%) and 125 out of 126 rifampin-susceptible isolates from Mexico (99%). DNA sequencing revealed that none of the nine rifampin-resistant isolates from Mexico, which were misidentified as rifampin susceptible by the molecular beacon assay, contained a mutation in the region targeted by the molecular beacons. The one rifampin-susceptible isolate from Mexico that appeared to be rifampin resistant by the molecular beacon assay contained an S531W mutation, which is usually associated with rifampin resistance. Of the rifampin-resistant isolates that were correctly identified in the molecular beacon assay, one contained a novel L530A mutation and another contained a novel deletion between codons 511 and 514. Overall, the molecular beacon assay appears to have sufficient sensitivity (89%) and specificity (99%) for use in countries with a high prevalence of tuberculosis.