From the Guidelines
Community-acquired cavitary pneumonia is most commonly caused by bacterial pathogens, including Streptococcus pneumoniae, Staphylococcus aureus, and Gram-negative pathogens such as Pseudomonas aeruginosa and Enterobacteriaceae. The microbial etiology of community-acquired pneumonia (CAP) is changing, particularly with the widespread introduction of the pneumococcal conjugate vaccine, and there is increased recognition of the role of viral pathogens 1. According to the American Thoracic Society and Infectious Diseases Society of America guidelines, the major treatable bacterial causes of CAP include Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Staphylococcus aureus, Legionella species, Chlamydia pneumoniae, and Moraxella catarrhalis 1.
Key Pathogens
- Streptococcus pneumoniae is the most common bacterial pathogen responsible for CAP, regardless of patient age and comorbidities 1
- Staphylococcus aureus, particularly MRSA, is a significant cause of community-acquired cavitary pneumonia
- Gram-negative pathogens, such as Pseudomonas aeruginosa and Enterobacteriaceae, are increasingly recognized as etiologic agents of CAP 1
- Other causes include Mycobacterium tuberculosis, fungal pathogens like Aspergillus species, and less common causes like Nocardia species and non-tuberculous mycobacteria
Diagnostic Workup
- Sputum cultures and blood cultures should be performed to identify the specific pathogen
- Bronchoscopy with bronchoalveolar lavage may be necessary in some cases to identify the pathogen
- Rapid diagnostics and molecular testing have improved the identification of co-existent pathogens 1
Treatment
- Empiric antibiotic therapy should typically cover MRSA, Pseudomonas, and anaerobes
- Vancomycin or linezolid can be used to cover MRSA, while piperacillin-tazobactam, cefepime, or a carbapenem can be used to cover Pseudomonas 1
- Metronidazole can be used to cover anaerobes if not already covered by other antibiotics
From the Research
Pathogens Causing Community-Acquired Cavitary Pneumonia
- Streptococcus pneumoniae is a common cause of community-acquired pneumonia (CAP) 2
- Haemophilus species, Legionella pneumophila, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli are also implicated in CAP 3
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of severe CAP, particularly in cases with cavitary consolidation, bilateral infiltrates, pleural effusion, and hemoptysis 4, 5
- Panton-Valentine leukocidin (PVL) producing MRSA is associated with necrotizing pneumonia and worse outcomes 4, 5
- Other pathogens, such as Mycoplasma pneumoniae and Chlamydophila pneumoniae, can also cause CAP 6
Characteristics of Community-Acquired Cavitary Pneumonia
- Can present with severe symptoms, including dyspnea, hemoptysis, and septic shock 4, 5
- Often requires hospitalization and aggressive treatment with intravenous antibiotics 4, 5
- Diagnosis can be challenging, with 30-65% of cases not having a pathogen isolated 2
- Molecular techniques, such as polymerase chain reaction, can improve diagnostic yield 2, 5