Pulmonology-Pulmonary Infections

Question 0

Clinical features pneumonia

Answer 0

fever and chills: organisms leak out into blood
cough with yellow-green (pus) or rusty sputum (blood)
tachypnea with pleuritic chest pain: when breathe in, stretch pleura –> pain (pleura is innervated, sensitize pleura via bradykinin and prostaglandin E2)
decreased breath sounds with dullness to percussion (replace air with consolidation due to exudate from inflammatory response)
elevated WBC count (infection)

Question 1

Pneumonia

Answer 1

Infection of lung parenchyma
Normal defenses impaired:
cough reflex, mucociliary escalator (viral pneumonia damages epithelial cells can get superimposed bacterial infection), mucous plugging of airway (infection behind the block)

Question 2

Pneumonia on CXR

Answer 2

Lobar: entire lobe with consolidation (airsacs filled with neutrophils + exudate of pneumonia )
–> bacterial
Bronchopneumonia: patchy manner in small airways (scattered patchy consolidation centered around bronchioles);
often multifocal and bilateral
–> bacterial
Interstitial pneumonia: increased lung markings
–> “atypical” (usually virus)

Question 3

Causes of Lobar pneumonia

Answer 3

Lobar:

1. Streptococcus pneumoniae (95%): most common cause CAP; usually middle aged adults and elderly
2. Klebsiella pneumoniae (5%): enteric flora that is aspirated
   - -> see in patients at increased risk for aspiration (malnourished and debilitated): elderly in nursing homes, alcoholics, diabetics

thick mucoid capsule –> gelatinous sputum (currant jelly sputum); part of what they cough up is thick mucoid capsule

often complicated by abscess

Question 4

Type II Pneumocyte

Answer 4

Stem cell of lung that helps regenerate lining of alveolar air sacs

Question 5

Causes of Bronchopneumonia

Answer 5

1. S.aureus: most common cause of secondary pneumonia (bacterial pneumonia superimposed on viral upper respiratory tract infection, which knocks out mucociliary escalator); often complicated by abscess or empyema (pus in pleural space)
2. Haemophilus influenzae: common cause of secondary pneumonia and pneumonia superimposed on COPD (leads to exacerbation of COPD)
3. Pseudomonas aeruginosa: pneumonia in cystic fibrosis
4. Moraxella catarrhalis: CAP and pneumonia superimposed on COPD (–> COPD exacerbation)
5. Legionella pneumophila: CAP, pneumonia superimposed on COPD, or pneumonia in immunocompromised states
   - -> transmitted from water source

intracellular organism best visualized by silver stain

Question 6

Interstitial (atypical) pneumonia

Answer 6

Diffuse interstitial infiltrates within lung (interstitium = connective tissue of alveolar airsacs)

inflammation not in alveoli/alveolar walls but alveolar walls/interstitium

“Atypical”
signs and symptoms: relatively mild upper respiratory symptoms (minimal sputum, cough, and low fever)

Question 7

Causes of Interstitial (Atypical) Pneumonia

Answer 7

1. Mycoplasma pneumoniae= most common cause atypical pneumonia
   young adults! (military recruits, college kids in dorms)
   complications: autoimmune hemolytic anemia (IgM against I antigen on RBCs –> cold hemolytic anemia), erythema multiforme
   *not visible on gram stain bc lacks cell wall)
2. Chlamydia pneumoniae: 2nd most common cause of atypical pneumonia in young adults
3. Respiratory syncytial virus (RSV): most common cause of atypical pneumonia in infants
4. Cytomegalovirus (CMV): atypical pneumonia with post transplant immunosuppressive therapy
5. Influenza virus: atypical pneumonia in elderly, immunocompromised, and those with preexisting lung disease;
   also increases risk for superimposed S.aureus* or H.influenzae bacterial pneumonia
   –> ppl don’t usually die of influenza but influenza virus weakens immune defenses –> susceptible to bacterial pneumonia (which then kills patient)
6. Coxiella burnetii: atypical pneumonia with high fever (Q fever); seen in farmers and veterinarians (coxiella spores)
   - -> rickettsial organism, but different from other rickettsiae bc:
7. causes pneumonia
8. does not require arthropod vector for transmission (heat resistant endospore)
9. does not produce skin rash

Question 8

Aspiration pneumonia

Answer 8

patients at risk for aspiration (alcoholics, comatose)

Pathogens (anaerobic bacteria from oropharynx):

1. Bacteroides
2. Fusobacterium
3. Peptococcus

Classically results in right lower lobe abscess
(anatomically right brainstem bronchus branches at less acute angle than left bronchus, much easier to go down right than left –> right lower lobe abscess)

Question 9

Primary Tuberculosis

Answer 9

inhalation of aerosolized mycobacterium tuberculosis

primary TB: focal caseating necrosis in lower lobe of lung + hilar lymph nodes
foci undergo fibrosis and calcification –> Ghon complex = nodule

Ghon complex classically subpleural

Primary TB generally asymptomatic but –> positive PPD

Question 10

Reactivation of TB (secondary TB)

Answer 10

AIDS, aging
Apex of lung where oxygen tension highest

foci of caseous necrosis
may develop miliary pulmonary TB (tiny regions of TB scattered throughout lung)
may develop tuberculous bronchopneumonia

Symptoms: fever, night sweats, cough with hemoptysis, weight loss
bx reveals caseating granulomas (ddx: TB and fungi; red acid-fast bacillus stain)

Question 11

Systemic spread of TB

Answer 11

any tissue can be involved
Meningitis: base of the brain! –> meningitis
Cervical lymph nodes
Kidney* most common organ involved –> sterile pyuria!
Lumbar vertebrae (Pott disease)