Pulmonology · IDSA

Community-acquired pneumonia

IDSA

Source:ATS/IDSA Clinical Practice Guideline on the Management of Community-Acquired Pneumonia (2019)

Verified Apr 2026

Ask House about this guideline

Red Flags

CAP with septic shock or respiratory failure (need for mechanical ventilation or vasopressors) — ICU; aggressive empirical broad-spectrum within 1 hour^[1]
CURB-65 ≥3 OR PSI class IV–V — admit; consider ICU if other major or 3 minor IDSA/ATS severity criteria met^[1]
Cavitation or necrotising pneumonia on imaging — broaden to MRSA/anaerobic coverage; investigate aspiration, immunosuppression, fungal aetiology^[1]
Fever and pulmonary infiltrate in immunocompromised host — opportunistic pathogens (PCP, fungi, atypical mycobacteria); empirical therapy + ID consult^[1]

First-line treatment

Interventions

Vaccination^[1]
Pneumococcal vaccination (PCV20 or PCV15+PPSV23) for adults ≥65 and high-risk; annual influenza vaccination; COVID-19 vaccination per current schedule

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Amoxicillin^[1]	Aminopenicillin	1 g PO TID for 5 days	80–90 mg/kg/day divided BD/TID	Outpatient CAP without comorbidities — no atypical coverage needed in healthy adults per shorter course
Amoxicillin-clavulanate or doxycycline^[1]	Beta-lactam-inhibitor or tetracycline	Amoxicillin-clavulanate 875/125 mg PO BD; doxycycline 100 mg PO BD for 5–7 days	Amox-clav 25–45 mg/kg/day	Outpatient CAP with comorbidities (diabetes, COPD, CKD, alcohol use) — atypical coverage warranted; doxycycline preferred over macrolide where local resistance to azithromycin is high
Ceftriaxone + azithromycin (inpatient non-ICU)^[1]	3rd-gen cephalosporin + macrolide	Ceftriaxone 1–2 g IV daily plus azithromycin 500 mg IV/PO daily for 5–7 days	Ceftriaxone 50 mg/kg/day	Standard inpatient regimen; respiratory fluoroquinolone (levofloxacin 750 mg) is alternative monotherapy
Beta-lactam + macrolide or fluoroquinolone (ICU)^[1]	Combination antimicrobial	Ceftriaxone 2 g IV daily + azithromycin 500 mg IV daily; OR ceftriaxone + levofloxacin 750 mg IV daily	—	Severe CAP requiring ICU; add MRSA cover (vancomycin or linezolid) if cavitation, post-influenza, IV drug use; add Pseudomonas cover (piperacillin-tazobactam or cefepime) if structural lung disease, prior MDR isolation
Oseltamivir (when influenza co-suspected)^[1]	Neuraminidase inhibitor	75 mg PO BD × 5 days	Weight-based	Add to antibiotics during influenza season if rapid test positive or high clinical suspicion

Amoxicillin^[1]

Aminopenicillin

Adult: 1 g PO TID for 5 days
Paediatric: 80–90 mg/kg/day divided BD/TID

Outpatient CAP without comorbidities — no atypical coverage needed in healthy adults per shorter course

Amoxicillin-clavulanate or doxycycline^[1]

Beta-lactam-inhibitor or tetracycline

Adult: Amoxicillin-clavulanate 875/125 mg PO BD; doxycycline 100 mg PO BD for 5–7 days
Paediatric: Amox-clav 25–45 mg/kg/day

Outpatient CAP with comorbidities (diabetes, COPD, CKD, alcohol use) — atypical coverage warranted; doxycycline preferred over macrolide where local resistance to azithromycin is high

Ceftriaxone + azithromycin (inpatient non-ICU)^[1]

3rd-gen cephalosporin + macrolide

Adult: Ceftriaxone 1–2 g IV daily plus azithromycin 500 mg IV/PO daily for 5–7 days
Paediatric: Ceftriaxone 50 mg/kg/day

Standard inpatient regimen; respiratory fluoroquinolone (levofloxacin 750 mg) is alternative monotherapy

Beta-lactam + macrolide or fluoroquinolone (ICU)^[1]

Combination antimicrobial

Adult: Ceftriaxone 2 g IV daily + azithromycin 500 mg IV daily; OR ceftriaxone + levofloxacin 750 mg IV daily
Paediatric: —

Severe CAP requiring ICU; add MRSA cover (vancomycin or linezolid) if cavitation, post-influenza, IV drug use; add Pseudomonas cover (piperacillin-tazobactam or cefepime) if structural lung disease, prior MDR isolation

Oseltamivir (when influenza co-suspected)^[1]

Neuraminidase inhibitor

Adult: 75 mg PO BD × 5 days
Paediatric: Weight-based

Add to antibiotics during influenza season if rapid test positive or high clinical suspicion

Safety-net

Take antibiotics for the full prescribed course even when feeling better — usually 5 days outpatient, longer inpatient^[1]
Worsening breathlessness, increasing chest pain, confusion, low urine output, or unable to tolerate oral fluids — same-day care; may need admission^[1]
Persistent symptoms despite 48–72 h of antibiotics or new fever — return for review; may need different agent or imaging for complications^[1]

Referral criteria

Severe CAP with septic shock or respiratory failureICU; broad-spectrum empirical including MRSA/Pseudomonas if risk factors^[1]
CURB-65 ≥3 or PSI class IV–VAdmit; ID consult if MDR risk^[1]
Pleural effusion >1 cm on lateral decubitusDiagnostic thoracentesis to exclude empyema; respiratory medicine for chest drain if complicated^[1]
Failure to improve at 48–72 h of empirical therapyReassess: cultures, atypical pathogens, MDR organism, complication (empyema), alternative diagnosis (PE, malignancy, organising pneumonia)^[1]

Clinical summary

Diagnosis, severity assessment, and antimicrobial therapy of community-acquired pneumonia in adults; risk-stratified inpatient vs outpatient management.

References

1.ATS/IDSA Clinical Practice Guideline on the Management of Community-Acquired Pneumonia (2019) (2019)

Drug

Class

Adult

Paediatric

Notes

Amoxicillin^[1]

Aminopenicillin

1 g PO TID for 5 days

80–90 mg/kg/day divided BD/TID

Outpatient CAP without comorbidities — no atypical coverage needed in healthy adults per shorter course

Amoxicillin-clavulanate or doxycycline^[1]

Beta-lactam-inhibitor or tetracycline

Amoxicillin-clavulanate 875/125 mg PO BD; doxycycline 100 mg PO BD for 5–7 days

Amox-clav 25–45 mg/kg/day

Outpatient CAP with comorbidities (diabetes, COPD, CKD, alcohol use) — atypical coverage warranted; doxycycline preferred over macrolide where local resistance to azithromycin is high

Ceftriaxone + azithromycin (inpatient non-ICU)^[1]

3rd-gen cephalosporin + macrolide

Ceftriaxone 1–2 g IV daily plus azithromycin 500 mg IV/PO daily for 5–7 days

Ceftriaxone 50 mg/kg/day

Standard inpatient regimen; respiratory fluoroquinolone (levofloxacin 750 mg) is alternative monotherapy

Beta-lactam + macrolide or fluoroquinolone (ICU)^[1]

Combination antimicrobial

Ceftriaxone 2 g IV daily + azithromycin 500 mg IV daily; OR ceftriaxone + levofloxacin 750 mg IV daily

—

Oseltamivir (when influenza co-suspected)^[1]

Neuraminidase inhibitor

75 mg PO BD × 5 days

Weight-based

Add to antibiotics during influenza season if rapid test positive or high clinical suspicion