Infectious Pulmonary Diseases

Objectives - Identify facts and principles about pneumonia and tuberculosis, including causes, classifications, pathogenesis, signs and symptoms, diagnostic testing, treatment, and infection control concerns.

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Pneumonia

Pneumonia is a lower respiratory tract infection that inflames the alveoli in one or both lungs. The alveoli may fill with fluid or pus.

High-yield burden and risk points from the source:

• Pneumonia is listed as the 8th leading cause of death in the U.S.
• About 5 million cases occur annually.
• About 1 million hospitalizations occur annually.
• The source lists 50,622 deaths.
• Risk groups include infants and young children, adults over 65, smokers, immunocompromised patients, and patients with recurring respiratory infections.

Pneumonia Causes

Pneumonia Classification

Classification is based on where pneumonia was acquired. This helps predict the likely cause and determine empiric antimicrobial therapy.

Pneumonia Pathogenesis

Pneumonia can develop through several routes:

• Inhalation of aerosolized particles from infectious patients, including COVID and TB.
• Aspiration from the oropharynx during sleep or with impaired gag reflex, narcotic use, alcohol intoxication, or stroke.
• Direct introduction into the lower airway, including frequent suctioning.
• Spread from adjacent organs, such as sub-diaphragmatic or liver abscesses.
• Spread through the blood, which is not common, such as right heart bacterial endocarditis or parasitic pneumonias.
• Reactivation of latent infection in immunosuppressed patients, including Pneumocystis jiroveci, M. tuberculosis, and cytomegalovirus.

Pneumonia Clinical Signs

Common clinical signs include:

• Pleuritic chest pain: sudden, intense, sharp, stabbing, or burning pain with inhaling and exhaling
• Dyspnea
• Expectoration and sputum production
• Fever and chills
• Muscle aches and stiffness
• Cough
• GI symptoms: nausea, vomiting, or diarrhea

Pneumonia Diagnosis

Diagnosis can include imaging, lab testing, and lower respiratory tract sampling.

Sputum Testing

Gram stain and culture place the sputum sample in growing media and analyze for growth. This helps determine the type of bacteria causing pneumonia.

Sensitivity testing determines whether a particular antibiotic or antifungal drug is likely to stop growth of the bacteria or fungi causing the infection.

Bronchoscopy and Mini BAL

Bronchoscopy can acquire lower respiratory tract samples when expectorated samples cannot be obtained or are nondiagnostic.

Bronchoscopy sampling methods include:

• Bronchoalveolar lavage (BAL)
• Routine brushing
• Protected specimen brushing

Mini BAL uses a telescoping catheter to sample lower respiratory tract secretions and improve accurate diagnosis of lung infection.

Pneumonia Treatment

Treatment options listed in the source include:

• Antibiotics
• Antivirals
• Antifungals
• Oxygen
• Fluids
• Airway clearance therapy

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Tuberculosis

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis. It may affect almost any tissue of the body, especially the lungs, and is characterized by tubercles.

Tuberculosis Classification

Active vs Latent TB

Tuberculosis Pathophysiology

TB is acquired by inhalation of airborne droplets containing M. tuberculosis.

Most individuals, 85-95% in the source, contain the infection and remain asymptomatic, but remain susceptible to reactivation later in life or if immunosuppressed.

The immune response produces a tubercle or caseous granuloma made of mononuclear cells and living TB, surrounded by white blood cells and fibroblasts that wall off the organism.

If the immune system cannot stop the infection:

• The organism continues to multiply.
• The center of the granuloma undergoes liquefaction called caseation.
• M. tuberculosis can escape the granuloma and infect other portions of the lungs.

Caseous necrosis is cellular death that usually occurs in the lungs. The dead lung cells develop a crumbly, dull white appearance that resembles cheese.

Tuberculosis Symptoms

Symptoms listed in the source include:

• Cough for at least 3 weeks
• Barking cough
• Hemoptysis
• Fever
• Weight loss
• Night sweats
• Fatigue
• Chest pain

Tuberculosis Diagnosis

Diagnosis can include:

• Patient clinical history and assessment
• Chest x-ray
• TB skin test using tuberculin purified protein derivative (PPD)
• Acid-fast bacilli smear or sputum cultures (AFB)
• Nucleic acid amplification test (NAAT), which detects genetic components of M. tuberculosis and is faster than AFB, less than 24 hours
• Blood tests using interferon gamma release assay (IGRA)

Sputum samples are collected in the morning on 3 consecutive days. If the patient cannot produce sputum, induced sputum or bronchoscopy may be performed.

Tuberculosis Treatment

Treatment lasts 6 to 12 months in the source.

The Bacille Calmette-Guerin (BCG) vaccination is not used in the U.S. and causes a false positive PPD.

Tuberculosis Infection Control

Hospitalized patients with suspected or confirmed TB must be placed in respiratory isolation and follow airborne precautions.

Required precautions include:

• Private room
• Negative pressure
• N95 masks for room entry
• Proper N95 fit
• Surgical mask for infected patients transported through the hospital

N95 designation means the respirator blocks at least 95% of 0.3 micron test particles if properly fitted.

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High-Yield Review