Orientation notes for study. Doses and regimens vary with local guidelines (Kenya MoH, hospital protocols): always check before prescribing.
Definition
Pneumonia is infection of the lung parenchyma (alveoli and interstitium) with consolidation: the air spaces fill with inflammatory exudate. It is the commonest cause of death from infection worldwide.
Classification
- Community-acquired (CAP): acquired outside hospital or within 48 hours of admission.
- Hospital-acquired (HAP): onset 48 hours or more after admission; ventilator-associated (VAP) after 48 hours of intubation.
- Aspiration pneumonia: inhaled oropharyngeal or gastric contents (stroke, alcohol, seizures, poor swallow); anaerobes; right lower lobe commonly.
- Immunocompromised hosts (HIV, steroids, chemotherapy): unusual organisms such as Pneumocystis jirovecii (PCP), TB, fungi, CMV.
- Anatomical: lobar, bronchopneumonia (patchy, often at the bases).
Causes (organisms)
| Setting | Common organisms |
|---|---|
| CAP | Streptococcus pneumoniae (commonest), Haemophilus influenzae, Mycoplasma pneumoniae, Legionella, Chlamydophila, viruses (influenza, RSV, SARS-CoV-2) |
| Post-influenza, IV drug use | Staphylococcus aureus (cavitating) |
| Alcoholism, aspiration, diabetes | Klebsiella pneumoniae ("redcurrant jelly" sputum, upper lobe), anaerobes |
| HAP / VAP | Gram-negative bacilli (Pseudomonas, Klebsiella, E. coli), S. aureus including MRSA |
| HIV | Pneumococcus, TB, PCP (dry cough, exertional dyspnoea, very low saturation, bilateral "ground-glass" infiltrates) |
| Atypical | Mycoplasma (young, extrapulmonary features, cold agglutinins), Legionella (hyponatraemia, diarrhoea, confusion) |
Kenya: think of pneumococcus, TB and HIV-related disease in every patient. Biomass smoke and malnutrition increase risk.
Clinical features
- Symptoms: fever, rigors, cough (productive, purulent or rusty), pleuritic chest pain, dyspnoea, malaise; confusion in the elderly, who may have few chest signs.
- Signs: tachypnoea, tachycardia, fever, cyanosis; chest: reduced expansion, dull percussion, bronchial breathing, coarse crackles, increased vocal resonance over the consolidation; pleural rub.
- Atypical pneumonia: gradual onset, dry cough, headache, myalgia, signs fewer than the X-ray suggests.
Severity assessment: CURB-65
One point each for: Confusion · Urea above 7 mmol/L · Respiratory rate 30 or more · Blood pressure low (systolic below 90 or diastolic 60 or below) · age 65 or more.
| Score | Risk | Usual place of care |
|---|---|---|
| 0–1 | Low | Home or outpatient |
| 2 | Moderate | Hospital |
| 3–5 | Severe | Consider ICU |
Also consider oxygen saturation (below 92%), multilobar involvement, comorbidity and social circumstances.
Investigations
- Chest X-ray: consolidation with air bronchograms; effusion; cavitation; multilobar.
- Pulse oximetry/arterial blood gas; FBC (raised white cells), CRP, U&E, LFTs.
- Blood cultures (before antibiotics in moderate or severe cases), sputum Gram stain and culture.
- Urinary antigens (pneumococcus, Legionella) where available.
- HIV test; sputum GeneXpert/AFB for TB in anyone with prolonged cough, weight loss, HIV or failure to respond.
- CT chest if the diagnosis is uncertain or complications are suspected.
Management
- Supportive: oxygen (target SpO2 94–98%; 88–92% if at risk of CO2 retention), IV fluids, analgesia (paracetamol, for pleuritic pain), nutrition, VTE prophylaxis.
- Antibiotics early (within 4 hours in severe disease). Typical approach:
- Low severity: amoxicillin (about 5 days).
- Moderate: amoxicillin plus a macrolide (clarithromycin) or doxycycline.
- Severe: IV broad-spectrum (for example co-amoxiclav or a cephalosporin such as ceftriaxone) plus a macrolide.
- Aspiration: amoxicillin-clavulanate or ceftriaxone plus metronidazole.
- HAP/VAP: guided by local resistance and cultures.
- PCP: high-dose co-trimoxazole plus steroids if hypoxic.
- ICU: NIV or ventilation, vasopressors for septic shock.
- Review at 48 hours; if no improvement, think of empyema, resistant or unusual organism, TB, obstruction (cancer), wrong diagnosis (PE, heart failure).
Complications
- Parapneumonic effusion and empyema, lung abscess, sepsis and septic shock, respiratory failure and ARDS, pleurisy, pericarditis, lobar collapse, metastatic infection (meningitis, endocarditis, arthritis), bronchiectasis (long term).
Follow-up and prevention
- Repeat chest X-ray at about 6 weeks in smokers or people over 50, to exclude an underlying cancer.
- Stop smoking; pneumococcal and influenza vaccines (and Hib/PCV in children); treat HIV; reduce biomass smoke exposure; good hand and oral hygiene.
Exam points
- Streptococcus pneumoniae is the commonest cause. Staph aureus follows influenza. Klebsiella in alcoholics.
- CURB-65 decides where to treat.
- Failure to improve: always think TB, empyema, cancer.
Pharmacology at a glance
Tap a drug name for its full card (how it works, adverse effects, cautions, dose), then use Back to this note to return to this spot. Condition guide: pneumonia drugs.
| Drug | Class | Role here | Watch for |
|---|---|---|---|
| Amoxicillin | Penicillin | First-line for low-severity community-acquired pneumonia | Rash, diarrhoea; allergy |
| Clarithromycin | Macrolide | Atypical cover added in moderate disease | QT prolongation, many interactions |
| Azithromycin | Macrolide | Atypical cover, or if clarithromycin interacts | QT prolongation |
| Doxycycline | Tetracycline | Alternative to a macrolide | Photosensitivity, oesophagitis |
| Co-amoxiclav | Penicillin plus β-lactamase inhibitor | Moderate to severe disease | Diarrhoea, liver injury |
| Ceftriaxone | Third-generation cephalosporin | Severe pneumonia (IV) | Biliary sludge, allergy |
| Benzylpenicillin | Penicillin | IV for severe pneumococcal pneumonia | Allergy |
| Metronidazole | Nitroimidazole | Added for aspiration pneumonia | Metallic taste; no alcohol |
| Cotrimoxazole | Sulphonamide combination | High-dose for Pneumocystis pneumonia in HIV | Rash, high potassium, low blood count |
| Paracetamol | Analgesic and antipyretic | Pleuritic pain and fever | Liver injury in overdose |
| Heparin | Low-molecular-weight heparin | Prevents clots in admitted patients | Bleeding, low platelets |
Timing matters: in severe pneumonia give the first antibiotic dose within 4 hours (sooner in sepsis), and take blood cultures first if this does not delay treatment.
Practice questions
1. A 70-year-old man is confused with RR 32, BP 88/50, urea 10 mmol/L and a right lower lobe consolidation. His CURB-65 score is: A. 2 · B. 3 · C. 4 · D. 5 · E. 1 Answer: D. Confusion, urea, RR, BP and age all score.
2. A man with HIV has weeks of dry cough and breathlessness on exertion with saturation 85% and bilateral ground-glass opacities. The most likely cause is: A. Streptococcus pneumoniae · B. Pneumocystis jirovecii · C. Klebsiella · D. Legionella · E. Mycoplasma Answer: B.
3. Pneumonia failing to improve after 5 days of antibiotics with a persistent fever. The next best step is: A. Stop antibiotics · B. Repeat imaging for empyema or abscess and look for TB or malignancy · C. Reassure · D. Add steroids alone · E. Discharge Answer: B.