Pneumonia: community-acquired
Community acquired pneumonia (CAP) may be caused by the following infectious agents:
Characteristic features of pneumococcal pneumonia:
Assessment
Severity may be stratified using the CRB-65 or CURB-65 scores (the latter requires a blood urea result).
CURB-65 score is calculated by giving 1 point for each of the following prognostic features:
Patients are stratified for risk of death as follows:
Management
For low and moderate severity pneumonia's it may be safe to discharge the patient with appropriate treatment but clinical judgement is required. Patients with severe pneumonia should be admitted.
In addition to antibiotic therapy the clinician will need to determine which patients require supplemental oxygen, fluid resuscitation and higher levels of cardiorespiratory support.
NICE have set out guidance on appropriate antibiotic therapy as shown in the table below:
- Streptococcus pneumoniae (accounts for around 80% of cases)
- Haemophilus influenzae
- Staphylococcus aureus: commonly after the 'flu
- Atypical pneumonias (e.g. Due to Mycoplasma pneumoniae)
- Viruses
- Klebsiella pneumoniae is rare and classically seen in alcoholics
Streptococcus pneumoniae (pneumococcus) is the most common cause of community-acquired pneumonia
Characteristic features of pneumococcal pneumonia:
- rapid onset
- high fever
- pleuritic chest pain
- herpes labialis
- lobar pneumonia is common
- Rust coloured sputum is sometimes seen due to haemorrhage into the alveoli
Assessment
Severity may be stratified using the CRB-65 or CURB-65 scores (the latter requires a blood urea result).
CURB-65 score is calculated by giving 1 point for each of the following prognostic features:
- Confusion (abbreviated Mental Test score ≤ 8 or less, or new disorientation)
- Urea > 7 mmol/L
- Respiratory rate ≥ 30 breaths per minute
- Low blood pressure (diastolic ≤ 60 mmHg or systolic <90 mmHg)
- Age 65 years or more.
Patients are stratified for risk of death as follows:
- 0 or 1: low risk (less than 3% mortality risk)
- 2: intermediate risk (3‑15% mortality risk)
- 3 to 5: high risk (more than 15% mortality risk)
Management
For low and moderate severity pneumonia's it may be safe to discharge the patient with appropriate treatment but clinical judgement is required. Patients with severe pneumonia should be admitted.
In addition to antibiotic therapy the clinician will need to determine which patients require supplemental oxygen, fluid resuscitation and higher levels of cardiorespiratory support.
NICE have set out guidance on appropriate antibiotic therapy as shown in the table below:
| Severity | Antibiotic(s) | Dosage | Course Length | Notes |
|---|---|---|---|---|
| Low severity (CRB-65 0 or CURB-65 0-1) | Amoxicillin | 500 mg three times daily (higher doses possible per BNF) | 5 days | First-choice oral antibiotic |
| Low severity | Doxycycline (alternative) | 200 mg first day, then 100 mg once daily | 5 days | For penicillin allergy or atypical pathogens suspected |
| Low severity | Clarithromycin (alternative) | 500 mg twice daily | 5 days | For penicillin allergy or atypical pathogens suspected |
| Low severity (pregnancy) | Erythromycin | 500 mg four times daily | 5 days | Alternative in pregnancy |
| Moderate severity (CRB-65 1 or CURB-65 2) | Amoxicillin +/- clarithromycin or erythromycin | Amoxicillin 500 mg three times daily. If atypicals suspected add clarithromycin 500 mg twice daily or erythromycin 500 mg four times daily | 5 days | Add macrolide if atypical suspected |
| Moderate severity (penicillin allergy) | Doxycycline or clarithromycin | Doxycycline 200 mg day 1 then 100 mg daily or clarithromycin 500 mg twice daily | 5 days | Guided by microbiology |
| High severity (CRB-65 3-4 or CURB-65 3-5) | Co-amoxiclav +/- clarithromycin or erythromycin | Co-amoxiclav 500/125 mg three times daily orally or 1.2 g three times daily IV. If atypicals suspected add clarithromycin 500 mg twice daily or erythromycin 500 mg four times daily | 5 days | IV or oral as appropriate, add macrolide for atypicals |
| High severity (penicillin allergy) | Levofloxacin | 500 mg twice daily orally or IV | 5 days | Consult microbiology if fluoroquinolone use uncertain |