What is the recommended evaluation and management for an otherwise healthy adult with mild‑moderate community‑acquired pneumonia, including outpatient antibiotic regimen and criteria for hospitalization (CURB‑65 (Confusion, Urea, Respiratory rate, Blood pressure, age ≥ 65), PSI (Pneumonia Severity Index))?

Management of Mild‑Moderate Community‑Acquired Pneumonia in Otherwise Healthy Adults

Outpatient Antibiotic Regimen

For previously healthy adults without comorbidities, prescribe amoxicillin 1 g orally three times daily for 5–7 days as first‑line therapy. This regimen retains activity against 90–95% of Streptococcus pneumoniae isolates, including many penicillin‑resistant strains, and provides superior pneumococcal coverage compared with oral cephalosporins 1, 2.

Alternative Oral Regimens

• Doxycycline 100 mg orally twice daily for 5–7 days is an acceptable alternative when amoxicillin is contraindicated, offering coverage of both typical bacterial pathogens and atypical organisms (Mycoplasma, Chlamydophila, Legionella) 1, 2.

• Macrolide monotherapy (azithromycin 500 mg day 1, then 250 mg daily; or clarithromycin 500 mg twice daily) should only be used in areas where documented pneumococcal macrolide resistance is <25%; in most U.S. regions resistance is 20–30%, making macrolide monotherapy unsafe as first‑line therapy 1, 2, 3.

Patients with Comorbidities or Recent Antibiotic Use

For adults with chronic heart, lung, liver, or renal disease; diabetes; alcoholism; malignancy; asplenia; or antibiotic use within the past 90 days, combination therapy is required 1, 2:

• Amoxicillin‑clavulanate 875 mg/125 mg orally twice daily plus azithromycin (500 mg day 1, then 250 mg daily) or doxycycline 100 mg twice daily 1, 2.

• Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) is reserved for patients with β‑lactam allergy or when combination therapy is contraindicated, acknowledging FDA warnings about serious adverse events (tendon rupture, peripheral neuropathy, aortic dissection) 1, 2.

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Criteria for Hospitalization

CURB‑65 Score (Simpler Tool)

Hospital admission is recommended for patients with a CURB‑65 score ≥2 1, 4. The CURB‑65 components are:

• Confusion (new disorientation to person, place, or time)
• Urea >7 mmol/L (or BUN >20 mg/dL)
• Respiratory rate ≥30 breaths/min
• Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg
• Age ≥65 years

Each criterion scores 1 point 1, 4:

• Score 0–1: Consider outpatient management
• Score ≥2: Hospitalization strongly recommended
• Score ≥3: Consider ICU admission 1, 4

Pneumonia Severity Index (PSI) (More Comprehensive)

The PSI is a validated 20‑variable prediction rule that stratifies patients into five risk classes 1, 5:

• PSI classes I–III: Appropriate for outpatient care unless unstable comorbidities, inability to take oral medication, or lack of adequate outpatient support exist 1, 5.
• PSI class IV: Consider hospitalization (physician discretion) 1, 5.
• PSI class V: Strong indication for inpatient admission 1, 5.

Using the PSI as an adjunct to clinical judgment reduces unnecessary variability in admission rates, decreases the high cost of inpatient pneumonia treatment, and minimizes the risk of hospital‑acquired complications 1.

Additional Clinical Adverse Prognostic Features Mandating Admission

Regardless of CURB‑65 or PSI score, hospitalize patients with any of the following 1, 4:

• Hypoxemia: oxygen saturation <92% or PaO₂ <8 kPa (60 mmHg) regardless of FiO₂ 1, 4
• Bilateral or multilobar involvement on chest radiograph 1, 4
• Respiratory rate >24 breaths/min 1, 4
• Inability to maintain oral intake (vomiting, severe nausea) 1, 4
• Altered mental status (confusion, lethargy) 1, 4
• Hemodynamic instability (systolic BP <90 mmHg, heart rate >100 bpm) 1, 4
• Significant comorbidities (COPD, diabetes, chronic organ disease, immunosuppression) that increase risk 1, 4, 3

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ICU Admission Criteria (Severe CAP)

Direct ICU admission is indicated when a patient meets one major criterion or ≥3 minor criteria 1, 4:

Major Criteria (Either One Mandates ICU)

• Septic shock requiring vasopressors 1, 4
• Respiratory failure requiring mechanical ventilation 1, 4

Minor Criteria (≥3 Mandate ICU)

• Respiratory rate ≥30 breaths/min 1, 4
• PaO₂/FiO₂ ratio <250 1, 4
• Multilobar infiltrates 1, 4
• Confusion (new disorientation) 1, 4
• Uremia (BUN ≥20 mg/dL) 1, 4
• Leukopenia (WBC <4,000 cells/mm³) 1, 4
• Thrombocytopenia (platelets <100,000 cells/mm³) 1, 4
• Hypothermia (core temperature <36°C) 1, 4
• Hypotension requiring aggressive fluid resuscitation 1, 4

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Treatment Duration and Monitoring

Duration of Therapy

• Minimum treatment duration is 5 days, continuing until the patient is afebrile for 48–72 hours with no more than one sign of clinical instability 1, 2.
• Typical total duration for uncomplicated CAP is 5–7 days 1, 2.
• Extended courses (14–21 days) are required only for infections caused by Legionella pneumophila, Staphylococcus aureus, or Gram‑negative enteric bacilli 1, 2.

Outpatient Monitoring

• Clinical review at 48 hours (or sooner if symptoms worsen) to assess symptom resolution, oral intake, and treatment response 1, 2.
• Indicators of treatment failure warranting hospital referral include: no clinical improvement by day 2–3, development of respiratory distress (respiratory rate >30/min, oxygen saturation <92%), inability to tolerate oral antibiotics, or new complications such as pleural effusion 1, 2.

Escalation Strategy for Treatment Failure

• If amoxicillin monotherapy fails, add or substitute a macrolide (azithromycin or clarithromycin) to cover atypical pathogens 1, 2.
• If combination therapy fails, switch to a respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1, 2.

Follow‑Up

• Routine follow‑up at 6 weeks for all patients; obtain a chest radiograph only if symptoms persist, physical signs remain abnormal, or the patient has high risk for underlying malignancy (e.g., smokers >50 years) 1, 2.

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Critical Pitfalls to Avoid

• Never use macrolide monotherapy in areas where pneumococcal macrolide resistance exceeds 25% (most of the United States); this leads to treatment failure and breakthrough bacteremia 1, 2, 3.

• Avoid indiscriminate fluoroquinolone use in uncomplicated outpatient CAP due to FDA warnings about serious adverse events (tendon rupture, peripheral neuropathy, aortic dissection) and rising resistance 1, 2.

• Do not use oral cephalosporins (cefuroxime, cefpodoxime) as first‑line agents for CAP because of their inferior in‑vitro activity against S. pneumoniae compared with high‑dose amoxicillin, lack of atypical coverage, higher cost, and no demonstrated clinical superiority 1, 2.

• Do not delay hospitalization in patients with CURB‑65 ≥2, PSI class IV–V, or any adverse prognostic features; outpatient management in these patients increases mortality 1, 4, 5.

• Elderly patients (≥65 years) frequently present without fever and with non‑specific symptoms (confusion, lethargy, general deterioration); do not delay diagnosis or treatment based on absence of fever 4, 3.

• Obtain blood cultures and sputum Gram stain/culture before initiating antibiotics in all hospitalized patients to enable pathogen‑directed therapy and safe de‑escalation 1, 2, 4.

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Prevention

• Administer pneumococcal polysaccharide vaccine to all adults ≥65 years and those with high‑risk conditions (chronic heart, lung, liver, or renal disease; diabetes; immunosuppression; asplenia) 1, 2, 4.

• Recommend annual influenza vaccination for all patients, especially those with chronic medical illnesses 1, 2, 4.

• Provide smoking‑cessation counseling to all current smokers 1, 2.