Pulmonary Infections - Pathoma Flashcards
What is the definition of pneumonia?
Infection of the lung parenchyma
When does pneumonia occur?
The normal defenses are impaired (e.g. cough reflex, damage to the mucociliary elevator)
What are the clinical features of pneumonia?
- Fever & chills
- Cough with yellow-green (pus) or rusty sputum (blood)
- Tachypnea with pleuritic chest pain (bradykinin and PGE2)
- Decreased breath sounds with dullness to percussion
- Elevated WBC count
What diagnostic tests help diagnose pneumonia?
- chest x-ray
- sputum gram stain and culture
- blood culture
What are the three patterns classically seen on chest x-ray in pneumonia?
1) Lobar pneumonia
2) Bronchopneumonia
3) Interstitial pneumonia (atypical pneumonia)
What is lobar pneumonia?
- Consolidation of entire lobe
- Usually bacterial
- Most common causes are: S pneumoniae (95%) and Klebsiella pneumoniae
What pathogen causes the majority of cases of community acquired pneumonia usually seen in middle-age and elderly adults?
Streptococcus pneumoniae
What organism affects malnourished and debilitated individuals, especially elderly nursing homes, alcoholics, diabetics, and people at increased risk for aspiration?
Klebsiella pneumoniae
What pneumonia-causing pathogen has a thick mucoid capsule that results in gelatinous sputum (currant jelly) and is often complicated by abscess?
Klebsiella pneumoniae
What are the four classic phases of lobar pneumonia?
- Congestion
- Red hepatization (exudate in the lungs containing PMNs & blood)
- Gray hepatization
- Resolution (regenerate tissue by type II pneumocyte)
What is bronchopneumonia?
Scattered, patchy consolidation centered around bronchioles; often multifocal and bilateral
What organism is the most common cause of secondary pneumonia (bacterial pneumonia superimposed on a viral upper respiratory tract infection)?
Staphylococcus aureus
often complicated by abscess or empyema
What is empyema
Pus in the pleural space
What organism is a common cause of secondary pneumonia and pneumonia superimposed on COPD (leads to exacerbation of COPD)?
Haemophilus influenzae
What pathogen commonly causes pneumonia in cystic fibrosis patients?
Pseudomonas aeruginosa
What organism is a common cause of community-acquired pneumonia and pneumonia superimposed on COPD (leads to exacerbation of COPD)?
Moraxella catarrhalis
What organism is a common cause of community-acquired pneumonia, pneumonia superimposed on COPD, or pneumonia in immunocompromised states, and is transmitted from water sources?
Legionella pneumophila (intracellular organsims that is best visualized by silver stain)
What is interstitial (atypical) pneumonia? How does it present?
- Diffuse interstitial infiltrates
- Presents with relatively mild upper respiratory symptoms (minimal cough, minimal sputum, and low fever)
What pathogen is the most common cause of atypical pneumonia, usually affects young adults (classically military recruits or college students living in a dormitory)?
Mycoplasma pneumoniae
What pathogen is not visible on gram stain due to lack of cell wall and often causes complications including autoimmune hemolytic anemia (Igm against I antigen on RBCs causing cold hemolytic anemia) and erythema multiforme?
Mycoplasma pneumoniae
What pathogen is the second most common cause of atypical pneumonia in young adults?
Chlamydia pneumoniae
What pathogen is the most common cause of atypical pneumonia in infants?
Respiratory Syncitial Virus
What pathogen causes atypical pneumonia in patients with post-transplant immunosuppressive therapy?
Cytomegalovirus (CMV)
What pathogen causes atypical pneumonia in the elderly, immunocompromised, and those with preexisting lung disease?
Influenza virus
also increases the risk for superimposed S. aureus or H. influenzae bacterial pneumonia
What pathogen causes atypical pneumonia with HIGH fever (Q fever) that is seen in farmers and veterinarians?
Coxiella burneti
Coxiella spores are deposited on cattle by ticks or are present in cattle placentas.
How is Coxiella different from Rickettsia?
Coxiella is a rickettsial organism, but it is distinct from most rickettsiae because it:
1) causes pneumonia
2) does not require arthropod vector for transmission (survives as highly heat-resistant endospores)
3) does not produce a skin rash
What type of patients get aspiration pneumonia?
Alcoholics, comatose patients
What type of bateria causes aspiration pneumonia?
Anaerobic bacteria in the oropharynx
e.g. Bacteroides, Fusobacterium, and Peptococcus
What does aspiration pneumonia classically result in?
right lower lobe abscess
What occurs pathologically after initial exposure of aerosolized Mycobacterium tuberculosis?
- Focal caseating necrosis in the lower lobe of lung and hilar lymph nodes
- Foci undergo fibrosis and calcification forming Ghon complex (subpleural fibrosed/calcified lung nodule)
What are the symptoms of Primary TB?
Primary TB is generally asymptomatic!
-but will still lead to postive PPD test
What occurs pathologically in Secondary TB?
Reactivation of TB:
- forms cavitary foci of caseous necrosis at apex of lung
- may also lead to miliary pulmonary TB or tuberculous bronchopneumonia
What are the clinical features of TB?
- Fevers and night sweats
- Cough and hemoptysis
- Weight loss
What does biopsy reveal in TB?
-Caseating granulomas
Where does TB have the potential to spread to?
- Can involve any tissue!
- Meninges (meningitis at base of brain)
- Cervical lymph nodes
- Kidney (sterile pyuria)
- Lumbar vertebrae (Pott disease)
