Week 3: Infections of the Lung

Question 1

Pneumonia vs pneumonitis

Answer 1

• pneumonia: exudative solidification (consolidation) of the lung parenchyma, generally as result of infectious agent.
• pneumonitis: term often used by some synonymously with pneumonia. Many non-infectious etiologies that result in pneumonitis such as radiation or hypersensitivity.

Question 2

List pulmonary defense mechanisms and some processes which may alter or destroy their activity

Answer 2

1. cough reflex
   - coma, depressed mental state, anesthesia, medications/drugs, neuromusclar disorders, surgery (thoracic/abdominal), epiglottic competency, tumors, intubation, trach
2. Muco-ciliary apparatus
   - cigarette smoke, noxious gases, viral infections, dehydration, mechanical obstruction, structural derangement, CF
3. Alveolar macrophages
   - O2 intox, EtOH, smoke, anoxia, drugs
4. cellular and humoral immunity
   - chemotherapy, malignancies, drugs and chemicals, general state of health, AIDS, immunosuppressive therapy
5. Misc factors: pulm edema, congestion, ischemia, infarc, coexistent disease, e.g. bacterial endocarditis

Question 3

Community-Acquired Acute Pneumonia.

Answer 3

• organisms: S. pneumoniae, H influenzae, M catarrhalis, S aureus, K pneumoniae, P aeruginosa, L pneumophila
• Congested vasculature followed by exudation of plasma, inflammatory cells, PMNs into alveolar lumen
• 2 patterns: Bronchopneumonia (mutli-focal) or Lobar

Question 4

4 stages of community acquired acute pneumonia

Answer 4

1. congestion
2. Red hepatization: congested vessels and inflammatory process
3. Gray hepatization: necrotic exudate and loss of congestion, white to gray purulent material.
   - CXR: consolidation
   - sputum microscopic: necrotic cellular debris, no organisms
   - organziation of exudate: fibrous plugs
4. resolution: if organization is quick, alveolar walls won’t have irreparable damage
   - resorption, phagocyctosis, expectoration of debris, leaving behind normal lung

Question 5

Community Acquired atypical pneumonia

Answer 5

• common in children and young adults
• organism: mycoplasma pneumonia. Then Chlamydia pneumonia, Q fever
• predominantly interstitial with widened septa and scattered mononuclear cells
• clinical: less sputum, no cough
• damaged URT epithelium inhibits mucociliary clearance and can lead to superimposed bacterial infections

Question 6

Hospital Acquired pneumonia

Answer 6

• predisposed because of mechanical ventilation, intravascular catheters, underlying disease, immunosuppression, prolonged antibiotic therapy
• organisms: E.coli, P. aeruginosa, S. aureus

Question 7

Aspiration pneumonia

Answer 7

• debilitated or unconscious individuals
• gastric/oral contents source of aspirate, may cause inflammatory run
• polymicrobial infection
• complication: formation of lung abscess

Question 8

local spread or dissemination of lung abscess can lead to:

Answer 8

• fibrinous pleuritis, empyema, mediastinitis, purulent pericarditis, infective endocarditis, otitis media, purulent meningitis, septic arthritis, renal infection, septi emboli
• Acute necrotizing pneumonia

Question 9

Chronic pneumonia

Answer 9

• usually localized, +/- lymph node involvement
• chronic granulomatous inflammation
• etiology: bacterial (mycobacterium tubuerculosis) or fungal (histoplasmosis, blastocycosis, coccidiomycosis)
• TB vs. Sarcoid: sarcoid is non necrotizing, clusters around vasculature and airways

Question 10

Initial infection by TB

Answer 10

• short acute inflammatory run
• usually asymptomatic involvement of small focus
• some bacterial drainage to regional lymph nodes
• strong T cell response, rapid
• caseating granulomatous reaction: “Ghon Focus)
• pulmonary lymph nodes: Ghon complex
• may become progressive, spread anywhere by blood
• military TB: millet seed pattern
• asymptomatic, at risk for reactivation forever
• primary site and regional nodes undergo calcification

Question 11

Fungal infections of lung-chronic TB

Answer 11

1. histoplasmosis
   - yeast at body temp, intracellular, GMS stain?
2. blastomycosis: PMNs/ granulomas
   - broad based budding
3. Coccidiomycosis
   - spherule filled with endospores

Question 12

Pneumonia in immunocompromised host and HIV

Answer 12

• Aspergillosis: can be septal hyphi, ball

- Pneumocytis jiroveci (PCP pneumonia): cysts look like crushed ping pong balls on silver stain

Question 13

Parasitic lung infections

Answer 13

• strongyloidiasis: HIV patients, round worm,
• dirofilariasis: Dog heart worm
• schistosomiasis: fluke
• echinococcosis: extension from liver infection, uncommon
• paragonimiasis: large eggs, flukes