Exploring tuberculosis by molecular tests on DNA isolated from smear microscopy slides.

Tuberculosis (TB) is an infectious disease of global public health importance caused by Mycobacterium tuberculosis complex. The disease has worsened with the emergence of multidrug-resistant (MDR)-TB strains. The timely diagnosis and treatment of TB remains a key public health priority, and laboratories have a critical role in the rapid and accurate detection of TB and drug resistance. Molecular assays based on nucleic acid amplification techniques have been developed for the rapid, sensitive, and specific diagnosis of TB, with the ability to determine the drug sensitivity status. These molecular techniques are now available or are being implemented in developing countries. However, traditional microscopy and culture methods cannot yet be replaced; the molecular assays can be applied in parallel with these tests for the diagnosis of TB or for drug susceptibility testing. Performing such molecular tests is often restricted by constraints with regard to sputum sample storage and safe transportation from remote health centres to central laboratories. Since smear slides are performed routinely for the diagnosis of TB in most TB diagnostic laboratories, they are readily available and could be the ideal tool to transport sputum for further molecular tests. The aim of this review was to provide a comprehensive survey on the use of smear slides for both TB diagnosis and the molecular test approach. Based on the literature, stained smear microscopy slides can be a safe system for the transportation of sputum specimens from remote health centres to reference TB laboratories for further molecular TB or MDR-TB detection, and could help in the rapid diagnosis and therefore timely management of TB patients.

Expression of TNF-alpha-dependent apoptosis-related genes in the peripheral blood of Malagasy subjects with tuberculosis.

The majority of Mycobacterium tuberculosis (Mtb) infections remain asymptomatic with only up to 10% progressing to clinical tuberculosis. However, the constituents of the effective "protective immunity" against tuberculosis responsible for containing most infections remain unknown. Evaluating gene transcriptional profiles in tuberculosis clinical cohorts is one approach to understanding the spectrum of tuberculosis progression. It is clear that apoptosis plays a role in the control of tuberculosis but the utility of apoptosis-related genes as surrogate markers of protection against tuberculosis has not been well investigated. To characterize potential surrogate markers that could discriminate different phases of the clinical tuberculosis spectrum, we investigated gene expression of several TNF-alpha dependent apoptotic genes (TNFR1, TNFR2, FLICE, FLIPs) by real-time RT-PCR of peripheral blood cells from cohorts of individuals with active tuberculosis or potential exposure to tuberculosis. Newly diagnosed tuberculosis patients (n = 23), their close household contacts (n = 80), and community controls (n = 46) were tested at intervals over a period of up to two years. Latent infection or previous Mtb contact was assessed by ELISPOT and TST and complete blood counts were performed during the follow up. Results showed significant upregulation of FLIPs expression by infected individuals regardless of clinical status at entry to the study. A higher percentage of lymphocytes was found in the infected household contacts that remained healthy. In contrast, in individuals with active TB, a significant upregulation of TNFR2 expression, a significantly higher percentage of monocytes and a significantly decreased lymphocyte count were seen, compared to subjects that remained healthy. Moreover, the household contacts who subsequently developed signs of TB also had a significantly high number of monocytes. These data suggest tuberculosis may be associated with decreased T-cell survival (perhaps due to apoptosis) while inhibition of apoptosis in monocytes could lead to a relative increase in these cells: a situation predicted to favour Mtb.

RFLP clusters of Mycobacterium tuberculosis strains from the Indian Ocean Region: local and South Asian characteristics.

This is the first study describing the genetic polymorphism of Mycobacterium tuberculosis strains in the Indian Ocean Region. Using IS6110 RFLP analysis, 475 M. tuberculosis isolates from Madagascar, Comoros, Mauritius, Mozambique and La Reunion were compared. Of the 332 IS6110 profiles found, 43 were shared by clusters containing 2-65 strains. Six clusters were common to at least two countries. Of 52 families of strains with similar IS6110 profiles, 10 were common to at least two countries. Interestingly, another characteristic was the frequency (16.8%) of IS6110 single-copy strains. These strains could be distinguished using the DR marker. This preliminary evaluation suggests genetic similarity between the strains of the Indian Ocean Region. However, additional markers would be useful for epidemiological studies and to assess the ancient transmission of strains between countries of this region.

RFLP clusters of Mycobacterium tuberculosis strains from the Indian Ocean Region: local and South Asian characteristics

This is the first study describing the genetic polymorphism of Mycobacterium tuberculosis strains in the Indian Ocean Region. Using IS6110 RFLP analysis, 475 M. tuberculosis isolates from Madagascar, Comoros, Mauritius, Mozambique and La Reunion were compared. Of the 332 IS6110 profiles found, 43 were shared by clusters containing 2-65 strains. Six clusters were common to at least two countries. Of 52 families of strains with similar IS6110 profiles, 10 were common to at least two countries. Interestingly, another characteristic was the frequency (16.8 percent) of IS6110 single-copy strains. These strains could be distinguished using the DR marker. This preliminary evaluation suggests genetic similarity between the strains of the Indian Ocean Region. However, additional markers would be useful for epidemiological studies and to assess the ancient transmission of strains between countries of this region.

African 1, an epidemiologically important clonal complex of Mycobacterium bovis dominant in Mali, Nigeria, Cameroon, and Chad.

We have identified a clonal complex of Mycobacterium bovis present at high frequency in cattle in population samples from several sub-Saharan west-central African countries. This closely related group of bacteria is defined by a specific chromosomal deletion (RDAf1) and can be identified by the absence of spacer 30 in the standard spoligotype typing scheme. We have named this group of strains the African 1 (Af1) clonal complex and have defined the spoligotype signature of this clonal complex as being the same as the M. bovis BCG vaccine strain but with the deletion of spacer 30. Strains of the Af1 clonal complex were found at high frequency in population samples of M. bovis from cattle in Mali, Cameroon, Nigeria, and Chad, and using a combination of variable-number tandem repeat typing and spoligotyping, we show that the population of M. bovis in each of these countries is distinct, suggesting that the recent mixing of strains between countries is not common in this area of Africa. Strains with the Af1-specific deletion (RDAf1) were not identified in M. bovis isolates from Algeria, Burundi, Ethiopia, Madagascar, Mozambique, South Africa, Tanzania, and Uganda. Furthermore, the spoligotype signature of the Af1 clonal complex has not been identified in population samples of bovine tuberculosis from Europe, Iran, and South America. These observations suggest that the Af1 clonal complex is geographically localized, albeit to several African countries, and we suggest that the dominance of the clonal complex in this region is the result of an original introduction into cows naïve to bovine tuberculosis.