Pneumonia is an acute infection of the pulmonary parenchyma , leading to inflammation and consolidation of the alveoli. The most common causative agent is Streptococcus pneumoniae , though other bacteria, viruses, and atypical organisms are also significant contributors.
Etiology: Common Pathogens
| Type | Organisms |
|---|---|
| Typical | Streptococcus pneumoniae , Haemophilus influenzae , Staphylococcus aureus |
| Atypical | Mycoplasma pneumoniae , Chlamydophila pneumoniae , Legionella pneumophila |
| Viral | Influenza virus, RSV, adenovirus, SARS-CoV-2 |
Clinical Presentation
- Fever, chills
- Productive cough (purulent or rust-colored sputum)
- Pleuritic chest pain
- Dyspnea, tachypnea
- Crackles or rales on auscultation
- Dullness to percussion and increased tactile fremitus in consolidation
🔑 High-Yield Pearl : In elderly patients, confusion and functional decline may be the only signs of pneumonia.
Diagnosis
Clinical Diagnosis
- Based on history and physical examination
- Respiratory symptoms with systemic features (fever, malaise)
Chest X-Ray (CXR)
- Not routinely indicated in uncomplicated outpatient cases.
- Indicated when:
- Diagnosis is uncertain
- Poor response to treatment
- Signs suggest pleural effusion , lung collapse , or mass lesion (e.g., smoker >50 years)
Laboratory Tests
- CBC (↑ WBC)
- CRP/ESR (nonspecific inflammation markers)
- Sputum Gram stain and culture
- Blood cultures if hospitalized
⚠️ Note : Always rule out tuberculosis in patients with persistent symptoms or at-risk groups.
Hospital Admission Criteria (Adults)
Consider hospital admission if one or more of the following are present (CURB-65/PSI Score considerations):
- Age > 65 years
- Confusion (new onset)
- Respiratory rate > 30/min
- Systolic BP < 90 mmHg
- Diastolic BP < 60 mmHg
- Oxygen saturation < 92%
- Comorbidities (COPD, CHF, diabetes)
🚩 High-Yield Tip : These features correlate with increased mortality risk .
Treatment
Adult Pneumonia Management
First-Line Antibiotic :
- Amoxicillin : 500 mg to 1 g TID (three times daily) for 5–7 days
If atypical pathogens suspected (e.g., M. pneumoniae , C. pneumoniae , L. pneumophila ) or poor response after 48 hours:
- Add:
- Doxycycline : 200 mg once, then 100 mg BID (twice daily) for 7 days
OR - Roxithromycin : 300 mg once daily for 7 days
- Doxycycline : 200 mg once, then 100 mg BID (twice daily) for 7 days
Penicillin Allergy :
- Monotherapy with doxycycline or roxithromycin
Avoid :
- Ciprofloxacin — poor activity against S. pneumoniae
💊 Antibiotic Stewardship Note : Tailor treatment based on local resistance patterns and culture results when available.
Pediatric Pneumonia Management
Hospital Referral Criteria
Refer if any of the following are present:
- Age < 6 months
- Drinking < 50% of usual intake
- SpO₂ ≤ 92%
- Severe tachypnea (e.g., RR > 60/min for infants)
- Decreased respiratory effort or apneic episodes
- Temp < 35°C or > 40°C
- Altered mental status (difficult to rouse)
- No clinical improvement after 24–48 hours of treatment
Pediatric Antibiotic Therapy
| Age Group | First-Line | Dose |
|---|---|---|
| All ages | Amoxicillin | 25–30 mg/kg/dose TID for 5–7 days |
| Age 3 months–5 years | Max dose: 500 mg/dose | |
| Age > 5 years | Max dose: 1000 mg/dose |
Alternatives :
- Erythromycin : 10–12.5 mg/kg/dose QID for 7 days
- Roxithromycin : 4 mg/kg/dose BID for 7–10 days
Only if the child can swallow tablets (may be crushed if necessary)
🧠 High-Yield Tip : In school-aged children, suspect atypical pneumonia —macrolides (e.g., erythromycin) are preferred.
Complications
- Parapneumonic effusion / Empyema
- Lung abscess
- Sepsis and septic shock
- ARDS
- Respiratory failure
Prevention
- Pneumococcal vaccination (PCV13, PPSV23)
- Influenza vaccination
- Smoking cessation
- Hand hygiene and infection control
Summary Table: High-Yield Facts
| Feature | High-Yield Point |
|---|---|
| Most common cause | Streptococcus pneumoniae |
| Key CXR finding | Lobar consolidation |
| Admission criteria | CURB-65 score or red flag vitals |
| Drug of choice (adults) | Amoxicillin |
| Drug of choice (children) | Amoxicillin (dosed by weight) |
| Suspect atypicals | Add doxycycline or macrolide |
| Prevention | Pneumococcal + flu vaccines |
