Disorders of the Lower Respiratory System: Tuberculosis

Core Concepts

The organism, latency, and reactivation

Mycobacterium tuberculosis grows slowly — so slowly that symptoms develop over weeks to months and treatment must continue for a long time. Its waxy cell wall makes it hardy and hard to destroy. Inhaled droplet nuclei reach the alveoli, where immune cells engulf the bacteria; in most people the immune response contains the infection, surrounding the bacteria with a wall of cells called a granuloma, where they can survive dormant for years or decades.

• Latent TB infection (LTBI): bacteria present but contained. No symptoms, normal chest findings, not contagious. Detected by a positive TB test in the absence of symptoms and active disease.
• Active TB disease: bacteria multiplying, causing tissue damage and symptoms. Commonly taught symptoms include a cough lasting weeks, sometimes with blood-streaked sputum (hemoptysis), night sweats, fever, weight loss, and fatigue. The person can spread the disease, primarily to close contacts.

The transition from latent to active is called reactivation, and it happens when immune defenses falter — classic triggers include HIV infection, immunosuppressive treatment, malnutrition, and other serious illness. Anyone can progress, which is why latent infection is treated, not merely observed.

Who is at risk

Risk falls into two buckets: exposure and progression. Exposure risk rises with close contact with someone with active disease, living or working in crowded settings (homeless shelters, prisons, long-term care), travel or residence in high-burden regions, and health care work itself. Progression from latent to active is driven by immune compromise (HIV, immunosuppressants), recent infection, and conditions such as diabetes or kidney failure. The nurse's history-taking — exposure, symptoms, immune status — feeds directly into testing decisions.

Testing: infection vs. active disease

Two common test approaches detect infection: the tuberculin skin test (TST/PPD) and the interferon-gamma release assay (IGRA), a blood test. A positive result means the person has been infected with the TB bacterium at some point — it does not mean they have active disease and does not by itself mean they are contagious. To diagnose active disease, clinicians combine symptoms, chest imaging, and laboratory tests of sputum (smear, culture, and molecular tests that detect the bacterium's genetic material). The nurse's role: prepare the person for testing, explain what results mean, and — critically — ensure that a positive test in a symptomatic person leads to evaluation for active disease rather than being treated as the final answer.

Treatment concepts: multidrug, long, and supervised

Active TB is treated with a combination of medications taken for many months; latent infection is also treated (with a shorter regimen) to prevent future reactivation. Regimen details change with guidelines, resistance patterns, and the individual case, so this topic deliberately names no drugs or durations. The concepts to internalize: (1) multiple drugs are needed, (2) the course is long, (3) adherence is everything, because stopping early selects for resistant bacteria, and (4) directly observed therapy (DOT) — watching the person take each dose — is a proven adherence strategy delivered by nurses and public health workers. Drug-resistant TB (including multidrug-resistant TB, MDR-TB) is a growing problem born largely from incomplete treatment.

Infection control and the nursing role

• Identify early: anyone with a persistent cough plus risk factors or classic symptoms is a candidate for prompt evaluation and isolation while the workup is underway.
• Isolate correctly: suspected or confirmed active TB of the lungs → airborne precautions: private negative-pressure room (if available), N95 or higher-level respirator for staff, restricted patient movement, per institutional policy.
• Teach the person and family: cough etiquette, why treatment must be completed, and how TB spreads (airborne, not by touch).
• Support adherence: DOT, reminders, addressing barriers (transportation, cost, side effects), and clear communication about follow-up testing; coordinate with public health for contact investigation.
• Person-first care: say "a person with TB," protect confidentiality, and counter stigma — TB carries social judgment that makes people hide symptoms and skip treatment.

Common Confusions