Colony Morphology & ID
Community-acquired pneumonia (CAP), healthcare-associated pneumonia (HCAP), and infections in cystic fibrosis (CF) patients are distinct clinical entities with unique diagnostic and therapeutic considerations. Understanding these differences is crucial for effective patient management
Community-Acquired Pneumonia (CAP)
- Definition: Pneumonia acquired outside of a healthcare setting
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Common Pathogens
- Streptococcus pneumoniae: Most common cause
- Haemophilus influenzae
- Moraxella catarrhalis
- Legionella pneumophila: Less common but important
- Staphylococcus aureus: Less common
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Diagnostic Approach
- Sputum: Sputum collection
- Gram Stain: Quality is assessed. Provides initial diagnostic information
- Culture: On BAP and CHOC. Culture allows the identification of the organisms
- Special Tests: Legionella
- Other Tests: Blood cultures
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Key Considerations
- Patient age, underlying medical conditions
- Severity of illness
- Presence of complications
Healthcare-Associated Pneumonia (HCAP)
- Definition: Pneumonia that develops in a patient with specific healthcare exposures, or with certain risk factors
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Pathogens
- High Risk of MDROs: Multidrug-resistant organisms (MDROs) are more common
- Acinetobacter baumannii complex
- Enterobacteriaceae (e.g., Klebsiella pneumoniae)
- Pseudomonas aeruginosa
- Stenotrophomonas maltophilia
- Staphylococcus aureus
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Diagnostic Approach
- Specimen Sources: Sputum, ETA, BAL
- Quantitative cultures may be used
- Culture and Gram stain on different types of media: including BAP, CHOC, and selective media
- Antimicrobial Susceptibility Testing: Essential to guide treatment
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Key Considerations
- Risk factors
- Presence of MDROs
- Prompt antibiotic therapy
Cystic Fibrosis (CF)
- Chronic, Polymicrobial Infections: Chronic infections
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Pathogens
- Pseudomonas aeruginosa: The most common, chronic
- Staphylococcus aureus: Early colonizer
- Haemophilus influenzae
- Burkholderia cepacia complex (Bcc): Serious, transmissible
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Diagnostic Approach
- Specimen Sources: Sputum, BAL
- Sputum Quality: This should be assessed
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Culture
- BAP and CHOC
- Selective media for Bcc
- Incubation times
- Antimicrobial Susceptibility Testing
- Identification: Species identification for Bcc
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Key Considerations
- Chronic infections
- Polymicrobial
- Antibiotic resistance
- Airway clearance
Key Differentiators
| Feature | CAP | HCAP | Cystic Fibrosis (CF) |
|---|---|---|---|
| Setting | Community | Healthcare | Chronic disease with respiratory involvement |
| Common Pathogens | S. pneumoniae, H. influenzae | MDROs: Acinetobacter, Enterobacteriaceae, Pseudomonas, S. aureus | Pseudomonas aeruginosa, S. aureus, Haemophilus influenzae, Burkholderia cepacia complex |
| Antibiotic Resistance | Less common | More common | Common, especially Pseudomonas |
| Specimen Source | Sputum | Sputum, ETA, BAL | Sputum, BAL |
| Reporting | Gram stain, culture, ID | Gram stain, culture, quantitative/semi-quantitative, ID, AST | Gram stain, culture, ID, AST |
| Additional factors | Patient’s health and clinical status | Healthcare risk, patient history | CF-specific issues and patient history |