Summary

2025 ATS/IDSA update to the 2019 CAP guideline addressing four focused questions in immunocompetent adults: lung ultrasound (LUS) as an alternative to chest radiography, empiric antibacterial therapy when a respiratory virus is detected, antibiotic duration shorter than 5 days after clinical stability, and adjunctive systemic corticosteroids in hospitalized CAP. Two questions are new (LUS, virus-positive empiric antibiotics) and two update 2019 recommendations (duration, steroids). The guideline emphasizes individualized care stratified by setting (outpatient vs inpatient) and severity (nonsevere vs severe CAP per 2007/2019 IDSA/ATS criteria); IDSA did not approve this update.

Key Recommendations

LUS is an acceptable diagnostic alternative to chest radiography for suspected CAP where appropriate clinician expertise exists (conditional, low-quality).
Adult outpatients without comorbidities with CAP and a positive respiratory virus test: do NOT prescribe empiric antibiotics (conditional).
Adult outpatients WITH comorbidities and a positive respiratory virus test: DO prescribe empiric antibiotics for possible bacterial-viral coinfection (conditional).
Adult inpatients with nonsevere CAP and positive viral test: prescribe empiric antibiotics (conditional, very low-quality).
Adult inpatients with severe CAP and positive viral test: prescribe empiric antibiotics (conditional, very low-quality).
Outpatients with CAP reaching clinical stability: treat with <5 days of antibiotics (minimum 3 days) rather than ≥5 days (conditional).
Inpatients with nonsevere CAP reaching clinical stability: treat with <5 days (minimum 3 days) rather than ≥5 days (conditional).
Inpatients with severe CAP reaching clinical stability: treat with ≥5 days rather than <5 days (strong recommendation).
Adult inpatients with nonsevere CAP: do NOT administer systemic corticosteroids (strong recommendation).
Adult inpatients with severe CAP: DO give systemic corticosteroids, EXCLUDING severe CAP caused by influenza (conditional).
When empiric antibiotics are started in virus-positive CAP, perform daily clinical and microbiologic reassessment to support early de-escalation or discontinuation.
Use macrolide monotherapy (azithromycin/clarithromycin) is NOT adequate for outpatient CAP in the US due to pneumococcal macrolide resistance; inpatients should receive β-lactam plus macrolide or fluoroquinolone.

Thresholds & Doses

Minimum antibiotic duration after clinical stability: 3 days (short-course floor); short-course threshold is <5 days vs ≥5 days.
Severe CAP definition: 1 major criterion (septic shock requiring vasopressors OR respiratory failure requiring mechanical ventilation) OR ≥3 minor criteria.
Severe CAP minor criteria include: RR >30/min, PaO2/FiO2 <250, multilobar infiltrates, confusion, BUN ≥20 mg/dL, WBC <4,000/μL, platelets <100,000/μL, temp <36°C, hypotension requiring aggressive fluid resuscitation.
Clinical stability criteria: temperature <37.8°C, HR <100 bpm, RR <24/min, SpO2 >90% or PaO2 >60 mm Hg on room air (or baseline O2), SBP >90 mm Hg, normal mental status.
Corticosteroid timing favoring benefit in severe CAP: administration within 24 h of meeting severe CAP criteria; weaker if >72 h from severe CAP onset.
Hydrocortisone regimen used in supporting trial (Dequin): 200 mg/day continuous IV infusion for 4 or 7 days, then taper to total 8 or 14 days (or stop at ICU discharge with rapid improvement).
LUS equipment: low-frequency probe with ~14–16 cm penetration in adults; standardized protocol covering superior and inferior anterior, lateral, and posterior chest.
Adequate fluoroquinolone dosing for CAP: levofloxacin 750 mg or moxifloxacin 400 mg.
PaO2/FiO2 <300 (respiratory failure) supports corticosteroid use in severe CAP.
Immunocompromise thresholds excluded from these guidelines: corticosteroids >20 mg/day prednisone-equivalent for >4 weeks, HIV with CD4 <200, solid organ transplant on antirejection therapy.

Citations

Summary of Recommendations, Question 1 — LUS as alternative to chest radiography (conditional, low-quality).
Summary of Recommendations, Question 2 — empiric antibiotics in virus-positive CAP across outpatient/inpatient strata.
Summary of Recommendations, Question 3 — <5-day antibiotic duration after clinical stability; strong recommendation for ≥5 days in severe CAP.
Summary of Recommendations, Question 4 — corticosteroids: strong against in nonsevere CAP, conditional for severe CAP excluding influenza.
Table 1 — patient factors strengthening/weakening each recommendation.
Table 2 — 2007/2019 IDSA/ATS severe CAP definition (major/minor criteria).
Table 4 — criteria for establishing LUS expertise (equipment, training, protocol, documentation).
Table 6 — clinical stability definitions used to trigger short-course antibiotic decisions.