What is the first phase of primary TB infection?

What is the first phase of primary TB infection?

• A. Latent TB Infection (LTBI) / Formation of Ghon Complex
• B. Initial Infection Phase
• C. Progressive TB Phase
• D. Secondary Reactivation Phase

Answer: (B)

The first phase of primary TB infection is the initial infection phase. After exposure, Mycobacterium tuberculosis is inhaled into the airways and taken up by alveolar macrophages. The bacilli begin to replicate within these immune cells, producing a local lesion called the Ghon focus in the lung. The bacteria then drain to regional hilar lymph nodes, leading to involvement of those nodes and forming what clinicians call a Ghon complex (the Ghon focus plus hilar lymph node). This combination represents the earliest stage of infection in primary TB. If the immune system walls off the infection, the bacteria can stay dormant, leading to latent TB infection rather than active disease. If containment fails, the disease can progress or reactivate later. So the initial infection phase best fits the very earliest events after exposure, before latency or reactivation.

The first phase of primary TB infection is the initial infection phase. After exposure, Mycobacterium tuberculosis is inhaled into the airways and taken up by alveolar macrophages. The bacilli begin to replicate within these immune cells, producing a local lesion called the Ghon focus in the lung. The bacteria then drain to regional hilar lymph nodes, leading to involvement of those nodes and forming what clinicians call a Ghon complex (the Ghon focus plus hilar lymph node). This combination represents the earliest stage of infection in primary TB.

If the immune system walls off the infection, the bacteria can stay dormant, leading to latent TB infection rather than active disease. If containment fails, the disease can progress or reactivate later. So the initial infection phase best fits the very earliest events after exposure, before latency or reactivation.