Describe the progression of infection in latent vs. active tuberculosis along with diagnostic criteria and treatment options

Question

What will be an ideal response?

Answer 1

Tuberculosis (TB) is a highly communicable bacterial disease spread by respiratory droplets. Despite a high global incidence and easy transmission, the vast majority of TB cases remain latent. In latent TB, inhaled bacteria are engulfed by phagocytes in the lungs. Some bacterial cells can survive inside the macrophage; however, these infected macrophages are detected by the immune system a walled off within a fibrous granuloma. Approximately 90% of such cases will remain latent for the rest of the patient's lifetime. The remaining cases will progress to active TB at some point in the future. Active TB develops when the center of the granuloma liquifies and breaks down, allowing bacteria to spread to other parts of the lung or other organs, and be transmitted to others. The most common screening test for TB is the tuberculin skin test; however, it can only show past exposure through infection or vaccination and cannot distinguish between active and latent TB. Interferon gamma assays and Xpert MTB/RIF likewise cannot differentiate active and latent TB. Culturing and microscopy of the acid-fast bacterium can detect active TB but not latent. A chest X-ray can be used on a patient who tests positive through a screening method and may detect lung damage due to active TB. Latent TB is treated with rifampin and/or isoniazid for 4 — 9 months. Active TB requires treatment with multiple antibiotics from 6 months to two years depending on the antibiotic-resistance profile of the strain involved.