Community-Acquired Pneumonia Management (ATS 2025)

Algorithm Steps

1. ▶

   Start

   START: Community-Acquired Pneumonia

   Acute lower respiratory infection with pulmonary infiltrate

   1. ●

      Action

      Confirm Diagnosis

      Clinical + radiographic

      • Acute onset cough + at least one of:
      • - Fever/hypothermia
      • - Dyspnea, tachypnea
      • - New focal chest findings
      • PLUS new pulmonary infiltrate on imaging
      • Consider COVID-19, influenza testing
      1. ◆

         Decision

         Severity Assessment

         Use validated scoring system

         • PSI (Pneumonia Severity Index): Class I-III = low risk
         • CURB-65: 0-1 = low risk, 2 = intermediate, 3-5 = high risk
         • Clinical judgment always required
         1. ●

            Action

            Outpatient Treatment

            Low severity, no comorbidities

            • PSI Class I-II OR CURB-65 0-1
            • No hypoxemia (SpO2 ≥92%)
            • Able to take oral medications
            • Adequate home support
            1. ◆

               Decision

               Comorbidities or Risk Factors?

               Determine antibiotic regimen

               • Comorbidities: CHF, COPD, CKD, DM, liver disease, alcoholism, malignancy, asplenia
               • Risk factors: Antibiotic use in prior 90 days, MRSA/Pseudomonas risk
               1. ●

                  Action

                  Healthy Outpatient

                  No comorbidities, no risk factors

                  • PREFERRED: Amoxicillin 1g PO TID x 5 days
                  • OR Doxycycline 100mg PO BID x 5 days
                  • Azithromycin 500mg day 1, 250mg days 2-5 (if local resistance <25%)
                  1. ✓

                     Outcome

                     Discharge

                     Complete course and follow-up

                     • Complete antibiotic course (5-7 days typical)
                     • Smoking cessation counseling
                     • Pneumococcal and influenza vaccines if indicated
                     • Chest X-ray at 6 weeks for smokers/age >50
                     • Return if worsening
               2. ●

                  Action

                  Outpatient with Comorbidities

                  Need broader coverage

                  • Amoxicillin-clavulanate 875/125 PO BID
                  • PLUS Azithromycin 500mg day 1, 250mg days 2-5
                  • OR Respiratory fluoroquinolone monotherapy:
                  • - Levofloxacin 750mg PO daily x 5 days
                  • - Moxifloxacin 400mg PO daily x 5 days
         2. ●

            Action

            Inpatient (Non-ICU)

            Moderate severity

            • PSI Class III-IV OR CURB-65 2
            • Hypoxemia requiring O2
            • Unable to take oral medications
            • Significant comorbidities
            1. ●

               Action

               Inpatient Non-ICU Antibiotics

               IV therapy

               • PREFERRED: Beta-lactam + Macrolide
               • - Ceftriaxone 1-2g IV daily + Azithromycin 500mg IV/PO daily
               • - Ampicillin-sulbactam 3g IV q6h + Azithromycin
               • ALTERNATIVE: Respiratory fluoroquinolone alone
               • - Levofloxacin 750mg IV daily
               • Duration: Minimum 5 days, afebrile ≥48h before stop
               1. ◆

                  Decision

                  Reassess at 48-72 Hours

                  Evaluate response

                  • IMPROVING: Afebrile, hemodynamically stable, improving respiratory status, able to eat
                  • NOT IMPROVING: Persistent fever, worsening hypoxemia, new infiltrates
                  1. ●

                     Action

                     IV to PO Switch

                     Transition and discharge planning

                     • Switch to oral when: Clinically improving, GI tract functional, no other IV needs
                     • Total duration: 5 days minimum (may extend if slow response)
                     • Discharge when stable on oral therapy
                  2. ⚠

                     Warning

                     Treatment Failure

                     No improvement at 48-72h

                     • Consider complications: Empyema, abscess, ARDS
                     • Broaden antibiotics
                     • CT chest
                     • Consider bronchoscopy
                     • Rule out non-infectious causes
         3. ⚠

            Warning

            ICU Admission

            Severe CAP

            • MAJOR CRITERIA (1 required): Septic shock, mechanical ventilation
            • MINOR CRITERIA (≥3 required): RR ≥30, PaO2/FiO2 ≤250, multilobar infiltrates, confusion, BUN ≥20, WBC <4K, platelets <100K, hypothermia, hypotension needing fluids
            1. ●

               Action

               ICU Antibiotics

               Aggressive coverage

               • Beta-lactam + Macrolide or Fluoroquinolone:
               • - Ceftriaxone 2g IV daily + Azithromycin 500mg IV
               • - OR Ceftriaxone + Levofloxacin 750mg IV
               • Add Vancomycin if MRSA risk factors
               • Add anti-pseudomonal if risk factors
               1. ◆

                  Decision

                  MRSA or Pseudomonas Risk?

                  Determine if additional coverage needed

                  • MRSA risks: Prior MRSA infection/colonization, recent hospitalization, hemodialysis, IV drug use
                  • Pseudomonas risks: Structural lung disease, frequent antibiotics, prior Pseudomonas
                  1. ●

                     Action

                     Add MRSA Coverage

                     If risk factors present

                     • Vancomycin 15-20 mg/kg IV q8-12h (target trough 15-20)
                     • OR Linezolid 600mg IV/PO q12h
                     • De-escalate if cultures negative at 48-72h
                  2. ●

                     Action

                     Add Pseudomonas Coverage

                     If risk factors present

                     • Piperacillin-tazobactam 4.5g IV q6h
                     • OR Cefepime 2g IV q8h
                     • OR Meropenem 1g IV q8h
                     • De-escalate based on cultures