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Tuberculosis pulmonar II: Fisiopatología
La tuberculosis, o TB, es una enfermedad infecciosa bacteriana causada por Mycobacterium tuberculosis. Si bien su impacto principal es en los pulmones…
La fisiopatología de la tuberculosis comienza cuando un huésped susceptible inhala gotitas en aerosol que contienen Mycobacterium tuberculosis.
Las gotitas llegan a los alvéolos de los pulmones, donde las bacterias se multiplican y se encuentran con macrófagos alveolares, que los engullen.
Sin embargo, en lugar de destruir las bacterias, los macrófagos les permiten sobrevivir y replicarse en su interior.
Después de 2 a 6 semanas, el cuerpo inicia una respuesta inmunitaria mediada por células, formando una estructura especializada llamada granuloma para contener la propagación bacteriana.
El granuloma está formado por células inmunitarias, células bacterianas vivas y muertas, células T y macrófagos.
Las bacterias pueden permanecer latentes dentro del granuloma, sin causar síntomas y sin ser contagiosas. Esta etapa se conoce como infección tuberculosa latente.
Si el sistema inmunitario está comprometido, la tuberculosis latente puede progresar a enfermedad tuberculosa activa a través del proceso de caseificación, en el que el centro de un granuloma se necrotiza, formando una sustancia parecida al queso llamada caseum.
Este material caseoso luego se erosiona en un bronquio, creando una cavidad que facilita la rápida proliferación bacteriana y la posible propagación de la infección a través de la sangre o la linfa
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Q1: How does Mycobacterium tuberculosis survive inside alveolar macrophages?
When susceptible hosts inhale aerosolized droplets containing Mycobacterium tuberculosis, the bacteria reach the lungs' alveoli where alveolar macrophages engulf them. However, instead of destroying the bacteria, the macrophages allow them to survive and replicate within. This intracellular survival mechanism enables the infection to establish and persist in the host.
Q2: What is a granuloma and why does the body form one?
A granuloma is a specialized immune structure that forms 2-6 weeks after infection when the body initiates a cell-mediated immune response. It comprises immune cells, live and dead bacterial cells, T-cells, and macrophages clustered together. The granuloma's primary function is to contain and prevent the spread of Mycobacterium tuberculosis throughout the body.
Q3: What is the difference between latent and active tuberculosis infection?
In latent tuberculosis infection, bacteria remain dormant within the granuloma, causing no symptoms and being non-contagious. Active tuberculosis disease develops when the immune system is compromised, allowing bacteria to multiply and spread, causing tissue damage and symptoms. About 5-10% of individuals with latent TB infection progress to active disease, particularly if their immune system becomes weakened.
Q4: How does caseation lead to cavity formation in tuberculosis?
Caseation occurs when the center of a granuloma becomes necrotized, forming a cheese-like substance called caseum. If this caseous material erodes into a bronchus, it creates a cavity that facilitates rapid bacterial proliferation. This cavitation process worsens symptoms and increases the potential for bacterial spread through blood or lymph.
Q5: How is tuberculosis transmitted from one person to another?
Tuberculosis transmission begins when a person inhales droplet nuclei containing Mycobacterium tuberculosis. These droplets are typically released into the air when an individual with pulmonary or laryngeal TB coughs, sneezes, or speaks. The inhaled bacteria then reach the alveoli in the lungs, where the infection cycle begins.
Q6: What role does the cell-mediated immune response play in tuberculosis infection?
Approximately 2-6 weeks post-infection, the body mounts a cell-mediated immune response where T cells recognize mycobacterial antigens presented by infected macrophages. This triggers cytokine release, activating other immune cells and processes that lead to granuloma formation. This immune response aims to contain bacterial spread and is essential for controlling the infection.
Q7: Can tuberculosis spread to organs outside the lungs?
Yes, from the lungs, Mycobacterium tuberculosis can spread through the bloodstream, causing miliary TB, or through the lymphatic system to other organs, resulting in extrapulmonary tuberculosis. This dissemination occurs when bacteria escape the primary infection site and establish secondary infections in various body systems, complicating the disease presentation and nursing management and prevention strategies.