Инфекционные заболевания: профилактика и контроль

Infection Congress 2018: Tuberculosis risk is spread within the hallmarks of the disease

Zlatko Dembic

Statement of the Problem: Heritable susceptibility to tuberculosis (TB) is complex and polygenic in nature. Only five to ten percent of humans that come in contact with the bacterium Mycobacterium tuberculosis (Mt) will manifest the disease, provided no acquired- or congenital immunodeficiency were present. We still lack a viable explanation for the observed epidemiologic fact. Method: Activation of macrophages via proinflammatory cytokines IFN-v and interleukin (IL)-17 can kill intracellular bacteria such as Mt. Instead, macrophages stimulated by the Toll-like receptor (TLR)-10 agonists show an anti-inflammatory effect. The TLR-10 acts by inhibiting the TLR-2 signaling from the cell membrane. The TLR-2 is the Mt-binding protein by which activated macrophages can internalize (and kill) Mt. Inactivation of the TLR-2 protein might convey a risk for developing the disease. This was supported by our finding that TLR2 gene polymorphisms, which either inactivate the TLR2 gene product or have a dominant negative role in TLR-2-signaling, associated with elevated risk for tuberculosis in the Croatian Caucasian population. Findings: The genome-wide study found that three single nucleotide polymorphisms (SNPs) within the HLA class II loci were significantly associated with TB; suggesting that adaptive immunity is of paramount importance for defense against TB. In our studied population, SNP in the TLR10 gene was associated with risk for TB, analyzed by the dominant model of inheritance. However, this was contrasted by the fact that SNPs in the IL17A&F genes were not. Conclusion & Significance: Studying genetic risk by association analyses or genome-wide screening led us to propose that clinical manifestation of TB is a state above certain risk-threshold. Threshold is reached by accumulation of seemingly minor susceptibilities divided between the hallmarks of the disease. The model suggests that every human population has its own mosaic of genetic risks for TB.


Notwithstanding giving compelling treatment and decreasing mortality, an essential point of tuberculosis (TB) control programs in nations of high TB rate is to lessen the transmission from irresistible TB cases. The advancement of TB in an uncovered individual is a two-phase process following disease. In most contaminated people, disease is contained by the safe framework, and microscopic organisms become walled off in caseous granulomas or tubercles. In about 5% of contaminated cases, fast movement to tuberculosis will happen inside the initial two years after disease. About 10% of individuals with the inactive contamination will reactivate, half inside the main year, the rest of their lifetime for the most part by reactivation of the lethargic tubercle bacilli obtained from essential disease or less much of the time by reinfection. Generally, around 10–15% of those contaminated proceed to build up the dynamic sickness at some stage sometime down the road, however the danger of movement is a lot higher at about 10% every year in HIV-positive and other immunocompromised people.

The danger of movement to contamination and illness is two unique viewpoints and legitimate comprehension of these variables is basic for arranging TB control procedures. The danger of disease following TB presentation is principally represented by exogenous factors and is dictated by a natural blend of the irresistibleness of the source case, nearness to contact, and social and conduct hazard factors including smoking, liquor, and indoor air contamination. In settings with expanded odds of social blending (along with congestion) transmission will be high. Thus, conditions that draw out the length of introduction to an irresistible patient incorporate wellbeing framework related figure, for example, postpone finding. Components that expand the movements of contamination to ailment are fundamentally endogenous (have related). Conditions that adjust the safe reaction increment the danger of movement to sickness with HIV coinfection, the most significant of these. Nonetheless, the populace level effect of this hazard factor could change contingent upon the neighborhood commonness of HIV. Diabetes, liquor, ailing health, tobacco smoke, and indoor air contamination are factors that sway a bigger area of the populace and quicken movement to TB malady. This paper means to sum up the hazard factors which add to TB contamination and illness at both individual and populace level.

Screening for TB (to analyze dormant TB contamination) and prophylactic treatment remain the most significant apparatuses to decrease the danger of movement to TB illness among high-chance people (close contacts, HIV tainted people, human services laborers, and so on.) and be considered in endemic nations to lessen the movement from contamination to sickness. Screening for idle TB likewise warrants exceptionally delicate and explicit instruments. The current exhibit (the recently accessible IGRAs) of analytic tests that distinguish idle TB disease are exceptionally explicit yet have diminished affectability. Their failure to separate inactive contamination from sickness and high operational costs makes them not exactly the perfect apparatus for use in the creating scene, where the majority of the TB disease and infection happens.

HIV coinfection is the most significant and intense hazard factor for TB contamination and infection. Intercessions, for example, early HIV directing and screening for TB patients and early determination and commencement of antiretroviral treatment (ART) to coinfected people have all been demonstrated to be viable in forestalling TB ailment.

In endemic nations, conclusion and treatment (through DOTS) of smear-positive cases remain the way to TB control by decreasing transmission from irresistible cases. Notwithstanding detached case-discovering rehearses, early determination of smear-positive cases can be improved through untargeted case-discovering techniques in endemic nations. Wellbeing framework issues hampering this incorporate a noteworthy rate (45% in nations like India) of TB patients getting to medicinal services through the private division. Such patients are unaccounted for, and along with the postponement in finding, they may go about as a consistent store for TB disease. Endeavors to incorporate private players (private experts, retail drug stores, and research centers) in TB control exercises are accordingly fundamental to shorten the pandemic.

The developing populace (particularly in nations like China and India) is probably going to expand the quantity of TB cases later on. Smoking rates are high among men in these endemic nations, and, along with increasing paces of diabetes, the danger of movement to TB malady will likewise increment. Intercessions, for example, smoking discontinuance and early screening for TB can be supported, however the effect of these mediations in diminishing TB chance stays immaterial at populace level.