The microbiology, epidemiology and investigation of community-acquired pneumonia (CAP)7 9
| Pathogen | Proportion of CAP cases (%) | Mode of lung invasion | Typical features | Epidemiological patterns | Microbiological investigations* |
|---|---|---|---|---|---|
| Streptococcus pneumoniae | 20–75 | A | Acute onset High fevers Pleuritic chest pain | Common during winter Men's shelters and prisons | Urine antigen test |
| Haemophilus influenzae | 3–10 | A | |||
| Moraxella catarrhalis | 3–5 | A | |||
| Mycoplasma pneumoniae | 1–18 | I | Epidemics spanning three winters every 4 years | Sputum PCR Throat swab PCR Complement fixation test | |
| Staphylococcus aureus | 1–5 | A | Preceded by viral infection (co-incident influenza virus infection in 39% of cases) | Most common during the winter | |
| Chlamydophilia pneumoniae | 4–6 | I | Prodrome of several days | Epidemics in the community and closed communities | Sputum antigen and/or PCR detection Complement fixation test |
| Coxiella burnetii | 2 | E | High fevers Dry cough | Cases commonly during April–June Epidemics related to animal sources | Serology |
| Legionella pneumophilia | 2–8 | E | Multisystem pathology (GI, neurological symptoms); biochemical abnormalities | Most common between June and October (peaks in August and September); 50% of cases related to travel, 93% of these to travel aboard (countries bordering the Mediterranean sea) | Urine antigen test Serology |
| Influenza A | 2–16 | I | Rhinitis and wheeze | Annual epidemics of varying magnitude during the winter | Nose and throat swab PCR |
*Pathogen-specific and in addition to blood, sputum and pleural fluid Gram stain, culture and sensitivities.
A, aspiration of oral and/or nasopharyngeal commensal; E, environmental source;9 ,12 GI, gastrointestinal; I, inhalation of infected droplets; PCR, polymerase chain reaction.