Respiratory Pathology Lecture 2 Flashcards
What is required for infection of the lungs?
- Defect in host defenses and/or pre-existing acute or chronic lung disease
- Markedly virulent organism
- Overwhelming infections
Predisposing factors to pneumonia (11)
- Extremes of age
- Altered consciousness: poor cough/expectoration and increased aspiration risk
- Cigarette smoking
- COPD
- Pulmonary Edema
- Malnutrition
- Immunosuppression
- Cystic fibrosis
- Immotile cilia
- Bronchial obstruction
- Viral URI w/secondary bacterial pneumonia
Clinical classification of pneumonia (4)
- Community acquired
- Hospital/healthcare facility acquired
- Immunocompromised
- Immunocompromised w/chronic pneumonia
Is “atypical” pneumonia milder or more severe than common bacterial pneumonia? How do you differentiate?
Atypical milder. Can’t differentiate clinically due to symptom overlap
What % of patients w/pneumonia may be afebrile?
20% esp. elderly
When and in who does leukopenia w/pneumonia usually occur?
Overwhelming infection. Esp. in infants and elderly.
How often is pneumonia etiology discovered w/max. lab effort?
Only 50-60% of patients
How often is causative bug of pneumonia identified in everyday clinical practice?
10-20%
How are most hospitalized pneumonia patients treated?
Empirically w/o bug I.D
How effective are empiric antibiotics in community acquired pneumonia?
> 95% of patients.
Microbiological means of dx of pneumonia (7)
- SPUTUM (stains, culture, PCR)
- Culture of aspirated pleural/empyema fluid or lung abscess
- Urinary antigen testing (pneumococcus, legionellaa)
- Lung biopsy (for culture and histology)
- Serology.
- Blood culture
- Procalcitonin (emerging test)
Is the organism identified from sputum or other respiratory secretions always causative of the patients pneumonia?
Not always. May just be a respiratory tract colonizer.
Which bugs if identified in lungs are always regarded as causative? Why is it important to identify these?
- Legionella
- Influenza
- M. tuberculosis
- C. psittasi
- Agents of bioterrorism
- Hanta virus, francisella tularensis, coxiella burnetii
- Fungal organisms (histoplasma, blastomyces, coccidioides)
These require different Rx than usual empiric antibiotics!
Most common bugs in community acquired pneumonia?
S. pneumoniae, mycoplasma pneumoniae, chlamydophilia pneumoniae, legionella, respiratory viruses
Most common overall causes of pneumonia?
Bacteria. Pneumococcus most common overall.
Patients w/prior flu, antibiotic rx, chronic pulmonary disease are at greater risk for pneumonia from what bugs?
S. aureus, enterobacteriaceae, pseudomonas
Most common bugs in ind. w/severe pneumonia w/ICU admit
S. pneumoniae, enteric gram - bacilli, S. aureus, legionella, H. influenzae, respiratory viruses, pneumocysitis jirovecii, mixed infections (immunosuppressed)
What is the most common cause of viral pneumonia in adults?
Influenza (A, B, avian)
How is viral pneumonia best diagnosed?
PCR
What are additional types of community-acquired pneumonias depending on endemic risk?
TB (esp. immigrant pop.
Fungal disease
S. pneumoniae info
- -colonizes up to 20% of adults
- -Most common cause of bacterial pneumonia
- -More definitive dx if bug grown in blood, pleural fluid culture or if + urine antigen test
- -Usually produce lobar pneumonia
- -Vaccine available against common serotypes for high risk ind.
H. influenzae info
- -Frequent pharyngeal colonizer
- -Pneumonia in adults and children
- -S/P type B vaccine (for encapsulated)
- -Most common type of bacterial pneumonia in COPD patients
Mycoplasma pneumoniae info
- -No cell wall
- -Up to 15% of community acquired pneumonia
- -Can have URI sx
- -Only serology to diagnose
Chlamydophilia pneumoniae info
- -Intracellular bacterium
- -5-10% community acquired pneumonia
- -Can have URI sx
- -Only serological dx
Legionella pneumophilia
- -2-9% community acquired pneumonia
- -Can have URI sx
- -Infection from aerosolized water droplets from water reservoirs
- -Often epidemic outbreaks
- -Favors patients w/predisposing chronic disease
- -Fatality up to 50%
- -Urinary antigen test/growth on diagnostic media
- -Associated with HYPONATREMIA
Gram - bacilli info
- -Common cause of hospital-acquired pneumonia
- -Typically severe and often require ICU care
- -Highest risk: mechanically ventilated patients
- -Klebsiella, pseudomonas aeruginosa, moraxella catarrhalis, other. misc. bugs (E. coli, enterobacter, acinetobacter)
Patients at highest risk for Klebsiella infection
COPD, diabetes, EtOH abuse, homeless
Patients at highest risk for psudomonas aeruginosa infection
CF, COPD, IPF, immunocompromised patients
Patients at highest risk for moraxella catarrhalis infection?
COPD, immunocompromised
Group A streptococcus info
–Can cause pneumonia w/early empyema formation in young/immunocompetent patients
Anaerobic bacteria info
–Typically associated w/aspiration of gastric contents
Aspiration pneumonia
Usually mixed anaerobic/aerobic infection combined w/chemical injury (frequent abscess formation)
Influenza info regarding pneumonia
- -Typically outbreaks of disease
- -Predominantly cause URI w/secondary risk of complicating bacterial pneumonia (esp. staph aureus).
- -Rapid PCR dx. can be important for guiding dx and rx
Varicella pneumonia
–Most common complication of varicella infection in healthy adults (10-30% mortality)
Hanta virus
Infected mice in SW USA
Flu-like sx, non-cardiogenic pulmonary edema
Fungal pneumonia in immunocompetent hosts (names of 3)
Histoplasmosis, blastomycosis, coccidiodomycosis
How does fungal pneumonia occur?
Inhalation of spores –> pulmonary infection +/- systemic spread
When is fungal pneumonia usually diagnosed?
–After failure of empiric antibacterial Rx for dx of common community acquired pneumonia
What does CT/CXR usually show w/fungal pneumonia?
May show ordinary pulmonary infiltrate or resemble a mass/tumor
Pathology of fungal pneumonia?
Necrotizing granulomas that can mimic TB and Wegener’s granulomatosis
Histoplasmosis info
- -OH/MS river valley regions
- -Bat/bird droppings
- -Cave explorers high risk
- -Flu-like sx w/pulmonary complaints
Histoplasmosis CXR and dx
- -CXR: can mimic sarcoidosis, TB, malignancy, associated w/mediastinal/hilar adenopathy
- -Respiratory secretions and tissue biopsy (culture, fungal stains, urine antigen testing, serology)
North American Blastomycosis info
- -Central/SE USA and Great Lakes region
- -Moist soil w/decaying vegetation
- -Direct or indirect spore inhalation
- -Nonspecific pulmonary sx (Cough, fever, sputum production)
- -Bloodstream dissemination (esp. to skin, bones/joints, GU)
Blastomycosis dx
Respiratory secretions (sputum and bronchial wash) and tissue bx for culture, fungal stains, emerging PCR methods
Coccidiomycosis info
SW USA/semi-desert to desert climates “Valley fever”
- -Ordinary community acquired pneumonia or flu-like sx
- -possible skin, bones/joints, CNS dissemination (like blasto)
Coccidiomycosis Dx and Rx
- -Dx: respiratory secretions, tissue bx for culture, fungal stains, serology, emerging PCR
- -Treat active pulmonary disease with antifungal drugs (usually -azoles, occasionally amphotericin B)
Pneumonia in immunocompromised individuals (common bugs)
- -Increased risk for all common causes of pneumonia
- -Nocardiosis
- -Pneumoncystis jirovecii
- -Cytomegalovirus
- -Herpes virus/varicella zoster
- -Atypical mycobacteria
- -Invasive fungal disease
- -Parasites
Key points about pneumonia in immunocompromised patients
- -Multiple different causative organisms possible
- -High index of suspicion if patient manifesting new pulmonary/febrile symptoms
- -Early imaging studies
- -Aggressive specific pathogen diagnosis needed
Pulmonary edema
Movement of fluid into alveolar spaces
Causes of pulmonary edema
- Hemodynamically increased alveolar capillary pressure (L HF = cardiogenic pulmonary edema)
- Alveolar microvascular injury (ARDS = non-cardiogenic pulmonary edema, high alt. or neurogenic pulmonary edema)
- Pulmonary edema w/mixed cardiogenic/ARDS features.
Cardiogenic pulmonary edema
- -Increased alveolar capillary pressure due to increased pulmonary venous pressure–> causes increased pulmonary interstitial fluid formation and then alveolar flooding
- -Most cases from LV failure
- -Some from vol. overload (IV or blood admin exceeding CV capacity)
Causes of LV failure
–Systolic or diastolic due to coronary disease, chronic HTN, cardiomyopathy, aortic valve disease, new-onset arrhythmias
Clinical presentation of cardiogenic pulmonary edema
- Acute dyspnea w/anxiety, diaphoresis, hypoxia
OR - More gradual onset of dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea with cough +/- frothy pink sputum
–If associated w/chest pain, think MI or aortic dissection
Cardiogenic pulmonary edema physical exam findings
Tachypnea, tachycardia, HTN or hypotension, cool extremities, rales +/- rhonchi/wheezes (1st in lung bases), cardiac murmurs (S3, valve-related), JVD
CXR findings w/cardiogenic pulmonary edema
Bilateral basilar interstitial/alveolar infiltrates +/- cardiomegaly
–Can be delayed up to 12 hrs in acute cases
BNP findings in cardiogenic pulmonary edema
> 400 high positive predictive value for CHF. (Less than 100 is a high negative predictive value)
Echocardiography
Good bedside assessment for evaluating LV systolic/diastolic function, cardiac pressures, valvular disease, pericardial effusion/tamponade
ARDS
Syndrome of acute respiratory distress
–Characterized by dyspnea, hypoxemia, diffuse pulmonary infiltrates on CXR
Pathology of ARDS
Diffuse alveolar damage w/alveolar hyaline membranes evolving to granulation tissue/organizing phase: either resolution or pulmonary fibrosis/death will occur
What is ARDS secondary to what type of previous insults within previous 2-3 days
Sepsis, trauma, pulmonary infection, gastric aspiration, inhaled irritants, transfusion, drug overdose, near drowning
