In spite of being one of our most prominent bacterial pathogens, the presence of small regulatory RNAs (sRNAs) has not previously been investigated in Mycobacterium tuberculosis. Post-transcriptional regulation of gene expression by sRNA molecules has been demonstrated in a wide range of pathogenic bacteria and has been shown to play a significant role in the control of virulence. By screening cDNA libraries prepared from low-molecular weight RNA from M. tuberculosis we have identified nine putative sRNA molecules, including cis-encoded antisense transcripts from within open reading frames and trans-encoded transcripts from intergenic regions. sRNAs displayed differential expression between exponential and stationary phase, and during a variety of stress conditions. Two of the cis-encoded sRNAs were associated with genes encoding enzymes involved in lipid metabolism, desA1 and pks12. These sRNAs showed complementarity to multiple M. tuberculosis genes, suggesting the potential to act as both cis-encoded and trans-encoded sRNAs. Overexpression of selected trans-encoded sRNAs had profound impact on growth of M. tuberculosis and M. smegmatis. This is the first experimental evidence of sRNAs in M. tuberculosis and it will be important to consider the potential influence of sRNA regulation when studying the transcriptome and the proteome of M. tuberculosis during infection.

Tuberculosis is recognized as the world's leading bacterial cause of death. Yet 95% of infection is believed to exist in an asymptomatic 'latent' form that is defined not by the identification of bacteria, but by the host immune response in the form of reactivity to tuberculosis proteins in the tuberculin skin test. It seems likely that clinically defined latent tuberculosis actually represents a spectrum that runs from elimination of live bacilli to subclinical disease: hence, it might be unhelpful to use a single term to describe all these conditions. To support this view, here we focus on recent increased understanding of the heterogeneity in both bacillary physiology and host immune response that potentially illuminates new therapeutic and diagnostic approaches to this condition.

BACKGROUND: Mycobacterium tuberculosis (MTB) is one of the leading causes of morbidity and mortality worldwide and infects approximately (1/3) of the human population, but only 10% of all infected individuals will ever develop the disease and half of these may result in a rapid progression to disease during the first 2 years after being infected. On the other hand, some phenotypic differences among mycobacterial strains contribute to variations in the outcome of the infection, e.g., the hypervirulent phenotype described in the Beijing family has been associated with the production of a phenolic glycolipid, which reduces the production of Th1 cytokines in the experimental model and requires the activity of a polyketide synthase enzyme encoded by the pks15/1 gene. METHODS: We analyzed clinical isolates characterized by recent transmission and rapid progression to disease to identify factors that may influence such behavior from a rural and semi-urban community in eastern Mexico. RESULTS: Using various typing tools, we were able to identify intrafamilial clusters which belonged to the East Asian lineage of MTB isolates (Beijing family) and another that belonged to the Indo-Oceanic lineage (Manila family). All isolates within these two clusters showed an intact pks15/1 gene sequence. Additionally, we identified three more family clusters that belonged to the Euro-American lineage and showed the typical 7-bp deletion of the pks15/1 gene. This 7-bp deletion was also found in the remaining 23 cases from non-family clusters. CONCLUSIONS: This is the first report of cases caused by strains with an intact pks15/1 gene in Mexico. Interestingly, we identified the three main mycobacterial lineages described so far: East-Asian, Indo-Oceanic, and Euro-American in a human population with almost no present-day migration.

The regulation of heat shock protein (HSP) expression is critically important to pathogens such as Mycobacterium tuberculosis and dysregulation of the heat shock response results in increased immune recognition of the bacterium and reduced survival during chronic infection. In this study we use a whole genome spotted microarray to characterize the heat shock response of M. tuberculosis. We also begin a dissection of this important stress response by generating deletion mutants that lack specific transcriptional regulators and examining their transcriptional profiles under different stresses. Understanding the stimuli and mechanisms that govern heat shock in mycobacteria will allow us to relate observed in vivo expression patterns of HSPs to particular stresses and physiological conditions. The mechanisms controlling HSP expression also make attractive drug targets as part of a strategy designed to enhance immune recognition of the bacterium.

Evaluation reports increasingly document the degree of program implementation, particularly the extent to which programs adhere to prescribed steps and procedures. Many reports are cursory, however, and few, if any, fully portray the long and winding path taken when developing evaluation instruments, particularly observation instruments. In this article, we describe the development of an observational method for evaluating the degree to which K-12 inquiry science programs are implemented, including the many steps and decisions that occurred during the development, and present evidence for the reliability and validity of the data that we collected with the instrument. The article introduces a method for measuring the adherence of inquiry science implementation and gives evaluators a full picture of what they might expect when developing observation instruments for assessing the degree of program implementation.

BACKGROUND: Inadequate understanding of the transmission of Mycobacterium leprae makes it difficult to predict the impact of leprosy control interventions. Genotypic tests that allow tracking of individual bacterial strains would strengthen epidemiological studies and contribute to our understanding of the disease. METHODOLOGY/PRINCIPAL FINDINGS: Genotyping assays based on variation in the copy number of short tandem repeat sequences were applied to biopsies collected in population-based epidemiological studies of leprosy in northern Malawi, and from members of multi-case households in Hyderabad, India. In the Malawi series, considerable genotypic variability was observed between patients, and also within patients, when isolates were collected at different times or from different tissues. Less within-patient variability was observed when isolates were collected from similar tissues at the same time. Less genotypic variability was noted amongst the closely related Indian patients than in the Malawi series. CONCLUSIONS/SIGNIFICANCE: Lineages of M. leprae undergo changes in their pattern of short tandem repeat sequences over time. Genetic divergence is particularly likely between bacilli inhabiting different (e.g., skin and nerve) tissues. Such variability makes short tandem repeat sequences unsuitable as a general tool for population-based strain typing of M. leprae, or for distinguishing relapse from reinfection. Careful use of these markers may provide insights into the development of disease within individuals and for tracking of short transmission chains.

Tuberculosis (TB) is a major threat to global health, recently exacerbated by the emergence of highly drug-resistant forms of the disease-causing pathogen and synergy with HIV/AIDS. In 2006, the Stop TB Partnership published "The global plan to stop TB: 2006-2015," which set out a vision of halving the prevalence of and mortality caused by the disease by 2015, followed by eliminating the disease as a public health problem by 2050. This vision depends on the development of improved diagnostics, simpler treatment, and more effective vaccination. Recently, active translational research pipelines directed toward each of these goals have been established, but improved understanding of the fundamental biology of this complex disease will prove to be the key to radical advances in TB control.

Asian immigrants to the United Kingdom demonstrate much higher tuberculosis rates than the indigenous population. This is postulated to be because of their low vitamin D levels, consequent upon a combination of diet and their reduced ultraviolet (UV) exposure in the United Kingdom, because vitamin D enhances antimycobacterial activity in in vitro systems. The aim of this study was to examine the relationship between UVB exposure, vitamin D levels and tuberculo-immunity in Asian immigrants in the United Kingdom. Suberythemal UVB treatments were given to eight subjects on 3 consecutive days, using broadband UVB fluorescent lamps. Blood was sampled for 25-hydroxyvitamin D (25-OH D) and whole blood functional assays were performed for antimycobacterial immunity. The mean 25-OH D level increased from a baseline of 11.23 ng/ml (95% CI 6.7-20.39) to 20.39 ng/ml (95% CI 16.6-20) following UVB treatment, P<0.01. However, no significant change in antimycobacterial immunity occurred following UVB exposure. This pilot study in Asian subjects with good baseline tuberculo-immunity has not supported a role for UVB-induced 25-OH D in the immune response to Mycobacterium tuberculosis.

In 2002, the prevalence of bovine tuberculosis (tb) among 500 cattle on Holeta Farm, near Addis Ababa, Ethiopia, was 48 per cent, and the farm was divided into positive and negative herds. After three consecutive rounds of skin testing and segregation of skin test-positive and -negative animals, the prevalence of bovine tb was reduced from 14 per cent to 1 per cent in the negative herd in a year. Spoligotyping of 41 isolates from 17 cows gave an identical and unique spoligotype pattern, which can be represented as the binary number 1100000101111110111111100010000000000100000, where 1 indicates the presence of a spacer and 0 represents a loss. This spoligotype pattern had not previously been reported on the Mycobacterium bovis spoligotype database, and it was therefore designated sb1176, Ethiopian M bovis strain 1 (embs1). The variable number tandem repeat (vntr) profile of the strain was 5254(*)33.1, which differed from the vntr profile of strains reported in Great Britain.

A mutant of Mycobacterium tuberculosis (Delta19) lacking the 19-kDa lipoprotein grows well in culture in vitro but was shown here to be essentially incapable of any significant replication in mice, even in mice lacking the gamma interferon gene. Despite this, mice inoculated with Delta19 were equally protected against an aerosol delivered challenge with M. tuberculosis compared to the conventional BCG vaccine. Cellular responses, including the generation of activated CD4 and CD8 cells secreting gamma interferon, were produced in similar numbers, and lung cells, particularly dendritic macrophages, exhibited high levels of Class-II MHC expression. These data show that despite being highly attenuated, the Delta19 mutant strongly retained vaccinogenic properties.