Typical setting | Pathogen(s) | Overall prevalence range | Comments |
Community-acquired | Streptococcus pneumoniae | 10 to 20% | Common cause of community-acquired pneumonia; PPE caused by S. pneumoniae are often monomicrobial. |
Microaerophilic streptococci - S. intermedius
- S. anginosus
- S. constellatus
| 4 to 24% | Common residents of oral flora; often associated with aspiration pneumonia and polymicrobial infection. |
Anaerobes, including*: - Fusobacterium nucleatum
- Prevotella species
- Peptostreptococcus species
- Bacteroides species
| 6 to 20% | Common residents of oral flora; often associated with aspiration pneumonia and polymicrobial infection. |
Hospital-acquired | Staphylococcus aureus | 10 to 15% | Most common cause of hospital-acquired infections. Frequently monomicrobial and can be associated with necrotizing or cavitary pneumonia. |
Gram-negative anaerobes and aerobes including: - Escherichia coli
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
| 8 to 10% | Other common causes of hospital-acquired infections. May be monomicrobial or polymicrobial, with polymicrobial infection more likely if associated with aspiration pneumonia. Pseudomonas may be associated with necrotizing or cavitary pneumonia. |