Contents · 12 sections
In a nutshell. Community-acquired pneumonia (CAP) is an acute infectious inflammation of the lungs that develops outside a hospital setting or within the first 48 hours of hospitalization. The most common pathogen is Streptococcus pneumoniae; atypical pathogens include Mycoplasma, Chlamydia, and Legionella; viruses include influenza and COVID-19. Diagnosis: clinical findings + chest X-ray (CT if doubtful). Scoring systems: CURB-65 (0–1 outpatient, 2 — hospitalization, ≥ 3 — ICU), PSI for risk stratification. Empirical ABT: outpatient — amoxicillin or amoxicillin/clavulanate ± macrolide; inpatient — ceftriaxone + macrolide; severe — carbapenem or ceftriaxone + levofloxacin + antistaphylococcal coverage. Vaccination — pneumococcal and influenza.
1. Definition and classification
- CAP is an acute infectious inflammation of lung tissue that occurs outside a hospital setting or within the first 48 hours of hospitalization in a patient without prior contact with healthcare facilities.
- Alternatives: hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), healthcare-associated pneumonia (HCAP — obsolete).
- By extent: focal, segmental, lobar, total.
- Incidence — 5–10 per 1000 adults per year; mortality is 1–5% in outpatients, 12% in inpatients, and 30–50% in the ICU.
2. Pathogens
| Pathogen | Proportion | Features |
|---|---|---|
| Streptococcus pneumoniae | 30–50 % | Lancet-shaped diplococci; "rusty" sputum, lobar consolidation |
| Haemophilus influenzae | 5–10 % | Frequent in smokers and patients with COPD |
| Mycoplasma pneumoniae | 5–15 % | Atypical, young adults; dry cough, interstitial changes |
| Chlamydophila pneumoniae | 5–10 % | Atypical |
| Legionella pneumophila | 1–5 % | Severe; hyponatremia, hepatitis, diarrhea; water-borne |
| Staphylococcus aureus | 1–5 % | Post-influenza, with necrosis, MRSA possible |
| Viruses (influenza, RSV, COVID-19) | 10–30 % | Often coinfection with bacteria |
| Pseudomonas aeruginosa | < 1–3 % | COPD, bronchiectasis, immunodeficiencies |
3. Clinical presentation
- Typical: fever, chills, cough with sputum, pleuritic chest pain, dyspnea.
- Physical examination: increased respiratory rate, percussion dullness, decreased breath sounds, fine moist rales, crepitation, bronchial breathing over the area of consolidation.
- Increased vocal fremitus and bronchophony.
- In elderly patients — often atypical: confusion, falls, decreased appetite without fever.
- Atypical pneumonia: fever from the first days, dry cough, headache, myalgia; elevated heart rate and mild auscultatory findings.
4. Diagnosis
- Chest X-ray in 2 projections is the main diagnostic method; focal/lobar infiltrates.
- CT — indicated for ambiguous X-ray findings, protracted course, or immunodeficiency.
- Complete blood count: leukocytosis (> 10 × 10⁹/L) with a left shift; ESR ↑, procalcitonin ↑ in bacterial infection.
- Biochemistry: creatinine, urea, liver function tests, electrolytes, glucose.
- Blood gases in severe cases — hypoxemia (SpO₂ < 92%).
- Sputum: Gram stain microscopy, culture with sensitivity testing.
- Blood cultures for severe CAP.
- Urinary antigen tests for pneumococcus and Legionella.
- PCR for respiratory viruses (influenza, SARS-CoV-2, RSV).
5. CURB-65 scale
| Criterion | Score |
|---|---|
| Confusion | 1 |
| Urea > 7 mmol/L | 1 |
| Respiratory rate ≥ 30/min | 1 |
| Blood pressure: SBP < 90 or DBP ≤ 60 mmHg | 1 |
| Age ≥ 65 years | 1 |
- 0–1 point: outpatient treatment, mortality < 3%.
- 2 points: hospital admission, mortality ~9%.
- ≥ 3 points: consider ICU admission, mortality 15–40%.
- CRB-65 (without urea) — used in the prehospital setting.
6. PSI scale (Pneumonia Severity Index)
- 20 parameters: demographics, comorbidities, physical exam, laboratory findings.
- Risk classes I–V:
- — Class I–II (≤ 70 points): outpatient, mortality < 1%.
- — Class III (71–90): evaluate individually.
- — Class IV (91–130): hospitalization, mortality 8–9%.
- — Class V (> 130): ICU, mortality 27–31%.
- More accurate, but more complex to use; CURB-65 is preferred at the bedside.
7. Severe CAP criteria (IDSA/ATS)
- Major criteria (≥ 1): mechanical ventilation or septic shock with vasopressors.
- Minor criteria (≥ 3 of 9):
- — Respiratory rate ≥ 30/min
- — PaO₂/FiO₂ ≤ 250.
- — Multilobar involvement.
- — Confusion.
- — Uremia (urea > 7).
- — Leukopenia < 4 × 10⁹/L.
- — Thrombocytopenia < 100.
- — Hypothermia < 36 °C.
- — Hypotension requiring fluid resuscitation.
8. Empirical antibiotic therapy (outpatient)
- Healthy patients without comorbidities: amoxicillin 1 g tid × 5–7 days or a macrolide (azithromycin, clarithromycin) if atypical pathogens are suspected.
- With comorbidities (COPD, diabetes mellitus, CHF, alcoholism, CKD): amoxicillin/clavulanate 875/125 mg bid + macrolide or respiratory fluoroquinolone (levofloxacin 750 mg/day, moxifloxacin 400 mg/day) as monotherapy.
- Duration 5–7 days; early switch to oral formulation upon improvement.
- Re-evaluation in 48–72 hours; if no effect, review diagnosis and treatment.
9. Empirical antibiotic therapy (inpatient)
- Inpatient, non-ICU: ceftriaxone 1–2 g/day + macrolide (azithromycin 500 mg/day) or respiratory fluoroquinolone monotherapy.
- ICU, no Pseudomonas risk: ceftriaxone 2 g/day + azithromycin or levofloxacin.
- ICU, Pseudomonas risk (COPD with frequent antibiotic use, bronchiectasis, systemic steroids, recent hospitalization): piperacillin/tazobactam or cefepime or carbapenem (meropenem) + macrolide or levofloxacin; + aminoglycoside in septic shock.
- MRSA risk: add vancomycin or linezolid.
- Influenza pneumonia — oseltamivir within the first 48 hours.
- IV → per os switch — upon clinical improvement, defervescence, stable hemodynamics and oxygen saturation.
10. Complications
- Parapneumonic effusion and empyema — thoracentesis + drainage in complicated cases (pH < 7.2, pus, large volume).
- Lung abscess — particularly Staph. aureus, anaerobes; drainage, prolonged antibiotic therapy.
- Sepsis and septic shock.
- Acute respiratory failure — need for mechanical ventilation.
- PE, AMI — frequently a trigger in the elderly.
- ARDS — particularly in viral or severe bacterial pneumonia.
11. Prevention
- Pneumococcal vaccination:
- — PCV13 (conjugate) + PPSV23 (polysaccharide) in individuals ≥ 65 years and risk groups.
- Influenza vaccine — annually.
- COVID-19 and pneumococcal vaccination post-COVID-19.
- HAP/VAP prevention — oral hygiene, semi-recumbent head position ≥ 30°, daily assessment of readiness for extubation.
- Smoking cessation, COPD management, glycemic control in diabetes mellitus.
12. FAQ
Is a follow-up chest X-ray needed after CAP treatment?
Yes, in 4–6 weeks for patients at high risk of lung cancer (smokers > 50 years, chronic patients) to rule out post-pneumonic tumor masking. In young patients without risk factors — based on clinical indications.
What is the duration of antibiotic therapy for CAP?
Usually 5–7 days; extension to 10–14 days in case of complications, slow clinical response, Legionella, Staph. aureus, or immunodeficiency.
How does CAP differ from acute bronchitis?
Bronchitis presents without an infiltrate on X-ray, is frequently viral, and antibiotics are usually unnecessary. CAP involves an infiltrate + fever + typical auscultatory findings, requiring antibiotics.
When are systemic glucocorticoids used?
In severe CAP with signs of systemic inflammatory response and in COVID-19 with hypoxemia — dexamethasone 6 mg/day × 10 days. Not routinely indicated in bacterial CAP; reserved for select patients with vasopressor-refractory septic shock.
What was healthcare-associated pneumonia (HCAP) and why was the term abandoned?
Previously, patients from nursing homes and dialysis centers were classified as HCAP with a high risk of MRSA/Pseudomonas. Since 2016, the IDSA has dropped the term as excessive empirical antibiotic therapy did not improve outcomes. Now, individualized risk factor assessment is used.
See also: COPD · Influenza · Sepsis · ARDS · Pulmonology Catalog