Tuberculosis

Tuberculosis Overview

Definition

  • Infectious disease caused by Mycobacterium tuberculosis.

Common Infection Site

  • Primarily affects the lungs, but can also infect other parts of the body such as the kidneys, spine, and brain.

Global Impact

  • Approximately one-third of the world's population is infected with TB, often in latent form, which can reactivate later in life.

  • TB is a major global public health issue, particularly in developing countries, and is among the top 10 causes of death worldwide.

Relation to HIV

  • TB is the leading cause of death among individuals with HIV/AIDS, with a synergistic relationship where each disease exacerbates the other.

Trends

  • In the United States, the prevalence of TB is decreasing due to effective public health interventions, such as screening and treatment programs.

Risk Factors for TB

Demographics:

  • Homeless individuals: Increased risk due to crowded living conditions and limited access to healthcare.

  • Residents of inner-city neighborhoods: Higher exposure to infection and poorer health resources.

  • Foreign-born persons: Higher rates of TB from countries with endemic levels of the disease.

Occupational Hazards:

  • Healthcare workers and individuals in close contact with TB patients are at increased risk.

  • People living or working in institutions, including prisons and shelters, are also at heightened risk.

Health Factors:

  • IV drug users: Increased susceptibility due to potential for compromised immune systems and poor health practices.

  • Immunosuppressed individuals: Including those on immunosuppressive medications or with chronic diseases, are at risk for both latent and active TB.

  • Poverty and limited access to healthcare lead to delayed diagnosis and treatment, increasing transmission risks.

Multidrug-Resistant Tuberculosis (MDR-TB)

Definition

  • Characterized by resistance to at least two first-line anti-TB drugs: Isoniazid and Rifampin.

Extensively Drug-Resistant TB (XDR-TB)

  • Defined as resistance to any fluoroquinolone and at least one injectable antibiotic, complicating treatment options and increasing mortality.

Causes of Resistance:

  • Incorrect prescribing: Inadequate dosing or inappropriate drug selection.

  • Lack of case management: Failure to properly follow up with patients on treatment.

  • Nonadherence to treatment: Patients skipping doses or stopping treatment early.

Etiology and Pathophysiology

Transmission:

  • TB spreads via airborne particles from an infected person, which can remain suspended in the air for minutes to hours.

  • Requires close, frequent, or prolonged exposure for transmission to occur; not spread through physical contact.

Infection Process:

  • Once inhaled, TB bacteria lodge in the bronchioles and alveoli, prompting local inflammatory reactions.

  • Formation of a Ghon lesion (calcified TB granuloma) containing the infection can occur, serving as a marker of latent infection.

  • It is estimated that only 5-10% of individuals infected with TB will develop clinical disease, especially if they remain immunocompetent.

Characteristics:

  • TB is aerophilic (requires oxygen), causing it to preferentially infect lung tissue, although it can disseminate through the lymphatic system to other organs.

Classification of TB

Latent TB vs. TB Disease:

  • Latent TB: TB bacteria are present but inactive; individuals are asymptomatic and cannot transmit the disease.

  • TB Disease: Bacteria are active; patients exhibit symptoms and can spread TB to others, posing serious health risks if left untreated.

Clinical Manifestations

LTBI (Latent Tuberculosis Infection):

  • Is typically asymptomatic, with no evidence of active disease.

Pulmonary TB Symptoms:

  • Initial dry cough that progresses to a productive cough over 2-3 weeks.

  • Constitutional symptoms: fatigue, malaise, anorexia, weight loss, low-grade fever, night sweats.

  • Late symptoms may include dyspnea (difficulty breathing) and hemoptysis (coughing up blood).

Symptoms in Severe Cases:

  • Coughing becomes frequent, and hemoptysis may occur in advanced stages; dyspnea is less common.

  • Immunosuppressed individuals may not exhibit classic symptoms; they may only show subtle changes, like alterations in cognitive function.

Complications of TB

Miliary TB:

  • Characterized by dissemination of large numbers of organisms via the bloodstream to distant organs; can be fatal if untreated.

  • Symptoms may include high fever, cough, lymphadenopathy, hepatomegaly, and splenomegaly.

Pleural TB:

  • Symptoms include chest pain, fever, cough, and may present with unilateral pleural effusion due to inflammatory response.

  • Can lead to empyema (accumulation of pus in the pleural space), indicating severe infection.

TB Pneumonia:

  • Develops from significant bacilli in the lungs, presenting similarly to bacterial pneumonia, complicating diagnosis.

Other Organ Impact:

  • TB can cause destruction in the spine (Pott’s disease), lead to bacterial meningitis, or cause peritonitis if gastrointestinal TB occurs.

Diagnostic Studies

Tuberculin Skin Test (TST):

  • Also known as Mantoux test, uses purified protein derivative (PPD) to assess for previous exposure to TB.

  • Results Interpretation: Induration of ≥15 mm indicates a positive test in low-risk individuals; immunocompromised patients may have differing thresholds.

False Negatives:

  • Patients may experience waning immune response, resulting in inaccurate test results; a two-step testing approach is recommended for at-risk individuals.

Interferon-γ Release Assays (IGRAs):

  • Tests that detect the T-cell response to TB antigens; include QuantiFERON-TB and T-SPOT.TB.

  • Provide quicker results but at a higher cost compared to TST.

Chest X-Ray:

  • Cannot confirm a TB diagnosis definitively and may appear normal even in active cases.

  • Indicators suggesting TB may include upper lobe infiltrates or cavitary lesions on imaging studies.

Bacteriologic Studies:

  • Essential for definitive TB diagnosis; entails taking consecutive sputum samples over three days, with culture results often taking weeks.

Interprofessional Care

  • Hospitalization is not generally required for most patients unless they exhibit severe symptoms or complications.

  • Patients remain infectious for the first 2 weeks after initiating treatment if their sputum tests positive for TB.

  • Drug therapy plays a crucial role in managing active cases; strict adherence to the treatment regimen is vital for successful outcomes.

Drug Therapy Overview

Active Disease Treatment:

  • Treatment is divided into phases:

    • Initial Phase: lasts 8 weeks, includes intensive drug therapy.

    • Continuation Phase: extends for 18 weeks, consolidating the treatment of TB.

  • Common regimens include Isoniazid, Rifampin, Pyrazinamide, and Ethambutol.

Patient Education:

  • Patients must be informed about potential side effects and the importance of reporting any adverse reactions; monitoring liver function is critical in patients receiving this therapy.

Directly Observed Therapy (DOT):

  • This strategy aims to prevent treatment noncompliance by having healthcare providers observe patients taking their medications.

Latent TB Treatment:

  • Typically treated with Isoniazid for 6-9 months, with alternative regimens available for those unable to tolerate standard therapy.

BCG Vaccine:

  • The BCG vaccine is used in select countries to protect against TB but is not routinely recommended in the U.S. due to variable effectiveness.

Nursing Implementation

Acute Care:

  • Isolation is crucial; patients should be placed in a single-occupancy room to prevent infection spread. Healthcare workers should use HEPA masks when caring for TB patients.

  • Prompt medical evaluation and initiation of appropriate drug therapy are necessary.

Preventing Spread:

  • Patient education on respiratory hygiene is vital, including thorough handwashing practices after handling tissues.

  • Patients should wear masks when outside of negative-pressure rooms to limit the risk of transmission.

Ambulatory Care:

  • Patients can be discharged even if cultures are still positive as long as they are stable; monthly follow-ups are essential to monitor treatment effectiveness.

  • Patients should be instructed on minimizing exposure to others and recognizing any symptoms of recurrence.

Health Department Notification:

  • Timely notification to public health authorities is critical for monitoring potential outbreaks and ensuring community safety.