– Acute infection of lung parenchyma acquired outside healthcare facilities.
– Caused by bacteria, viruses, or fungi.

– Common type of lower respiratory tract infection (LRTI).
– Occurs in individuals not recently hospitalized or in long-term care.

– Varied outcomes: Complete resolution with oral antibiotics to hospitalization for IV antibiotics.
– High morbidity and mortality potential.

– Tools like CRB-65 score help determine appropriate clinical care based on severity.

Bacterial Pathogens:
– Streptococcus pneumoniae
– Haemophilus influenzae

Atypical Bacteria:
– Mycoplasma pneumoniae
– Chlamydophila pneumoniae
– Legionella pneumophila

Respiratory Viruses:
– Influenza viruses
– Respiratory syncytial virus (RSV).

– Advanced age.
– Smoking.
– Chronic lung diseases (e.g., COPD).
– Immunosuppression.
– Comorbidities (e.g., diabetes, heart disease).
– Environmental exposure (e.g., air pollution, occupational hazards).
– Impaired swallowing reflex (dysphagia).

– Microorganism Entry: Inhalation or aspiration of infectious agents into the lower respiratory tract.
– Lung Tissue Invasion: Microorganisms invade lung tissue, triggering an inflammatory response.
– Immune Response: Immune system activates to control the infection, causing inflammation and alveolar consolidation.
– Impaired Gas Exchange: Inflammation and consolidation impair gas exchange in the alveoli.
– Clinical Presentation: Severity of the inflammatory response influences clinical presentation and complications of CAP.

• Common symptoms: Cough, sputum production, dyspnea, chest pain, fever, fatigue.
• Older adults: May present with headache, muscle aches, and confusion.

• Diagnosis: Based on typical symptoms like fever, productive cough, dyspnea, pleuritic chest pain.
• Severity Assessment: CRB-65 or CURB-65 scoring system.

• CRB-65 Score Criteria:
– C: Confusion – 1 point.
– R: Respiratory rate ≥ 30 breaths/minute – 1 point.
– B: Blood pressure < 90/60 mm Hg - 1 point.
– 65: Age ≥ 65 years – 1 point.

• Interpretation:
– Score 0: Low risk, consider home treatment.
– Score 1-2: Intermediate risk.
– Score 3-4: High risk, consider hospitalization.

• CURB-65 Score: Used in hospital settings and includes urea measurement.
• Criteria:
– C: Confusion – 1 point.
– U: Urea > 7 mmol/L – 1 point.
– R: Respiratory rate ≥ 30 breaths/minute – 1 point.
– B: Blood pressure < 90/60 mm Hg - 1 point.
– 65: Age ≥ 65 years – 1 point.

• Interpretation:
– Score 0-1: Low risk, home treatment.
– Score 2: Intermediate risk, consider hospitalization.
– Score 3 or more: High risk, hospital admission, assess need for intensive care.

• Chest X-ray (CXR): Evaluates lung infiltrates or consolidation; particularly important if there is diagnostic uncertainty, poor treatment response, or suspected underlying lung pathology.
• Laboratory Tests:
– Full Blood Count (FBC): Provides general information about infection.
– C-reactive protein (CRP): Indicates severity of infection.
– Blood Cultures: Helps identify causative pathogens.

• Sputum Culture: Identifies pathogens in sputum samples.
• Respiratory Viral Panels: Detect specific viral pathogens.

• Typically, basic observations like blood pressure and pulse oximetry are sufficient.
• Extensive investigations are usually not required for community-managed cases.

• Reserved for patients requiring hospitalization (moderate to high severity CAP).
• Blood Cultures: Preferably taken before starting antibiotics.
• Sputum Culture and Sensitivity: Helps identify pathogens in sputum.
• Investigations for Atypical Bacteria and Pathogens:
– Legionella pneumophila.
– Mycoplasma pneumoniae.
– Chlamydophila pneumoniae.

Antibiotic Treatment:
– Empirical antibiotics guided by local protocols.
– Low Severity: Oral amoxicillin (500 mg) for 5-7 days.
– Moderate Severity: Oral/IV amoxicillin + macrolide (e.g., clarithromycin) for 7-10 days.
– Severe: IV co-amoxiclav (or other broad-spectrum β-lactamase) + macrolide; switch to oral after improvement.

Supportive Care:
– Oxygen therapy if hypoxia is present.
– Fluids if dehydration is present.

Follow-Up:
– Recommend follow-up at 6 weeks.
– Clinical review by GP or hospital outpatient clinic.
– Follow-up CXR if signs persist or if there’s a risk of underlying lung pathology.

Vaccinations: Offer influenza and pneumococcal vaccination to high-risk patients (e.g., adults over 65-years-of-age).

– Factors affecting prognosis: Age, overall health, illness severity, prompt treatment.
– Favorable outcome: Most recover with antibiotics and support.
– Severe cases: Higher risk of complications and mortality.
– Early intervention: Prompt recognition and treatment improve prognosis.

– Respiratory Failure
– Sepsis
– Pleural Effusion
– Lung Abscess
– Acute Respiratory Distress Syndrome (ARDS)

These complications may require:
– Intensive care support.
– Invasive procedures (e.g., chest tube placement).
– Extended hospitalization.
– CAP can worsen underlying chronic lung conditions (e.g., COPD) and increase the risk of long-term respiratory impairment.