Pneumonia (main)

This page is for adult patients. For pediatric patients, see: pneumonia (peds)


  • Definition: infection of lung parenchyma
  • Empirically classified based upon location/risk factors

Hospital-acquired pneumonia (HAP)

  • HCAP no longer entity in ISDA/American Thoracic Society guidelines[1]
  • ISDA recommends only covering empirically for MRSA or pseudomonas in adults with CAP if "locally validated" risk factors for either pathogen and then, continuing empiric coverage while obtaining culture data to justify extended coverage
  • Commonly accepted risk factors for resistant pathogens (e.g. MRSA, pseudomonas) historically include:
    • Hospitalized for 2 or more days within past 90 days
    • Nursing home/long-term care residents
    • Receiving home IV antibiotics
    • Dialysis
    • Receiving chronic wound care
    • Receiving chemotherapy
    • Immunocompromised

Pseudomonas risk factors

  • Alcoholism
  • Immunosuppression (including steroids)
  • Structural lung disease
  • Malnutrition
  • Recent antibiotics
  • Recent hospital stay

Causes of Pneumonia





Commonly Encountered Pathogens by Risk Factor

Risk Factor Associated Organism
COPD and/or Smoking
Nursing Home
Exposure to bird droppingsHistoplasma capsulatum
Exposure to birdsChlamydophila psittaci
Exposure to rabbitsFrancisella tularensis
Exposure to farm animalsCoxiella burnetii (Q fever)
Exposure to southwestern USCoccidiomycosis (Valley fever)
Early HIV
Late HIV (as above, plus:)
  • Pneumocystis jiroveci
  • Cryptococcus
  • Histoplasma
Structural Lung Disease (CF, bronchiectasis)
Injection drug use
Ventilator Associated Pneumonia

Clinical Features

Differential Diagnosis

Acute dyspnea




  • CXR
    • May have negative CXR early in disease or in cases of dehydration; infiltrate may "blossom" after providing rehydration and repeat imaging[2]
    • Absence of CXR findings does not preclude diagnosis; high clinical suspicion with adventitious breath sounds can be consistent with pneumonia despite negative imaging
    • Immunocompromised patients may not manifest radiographic evidence of pneumonia despite suggestive clinical findings
    • Clinical and radiographic findings do not necessarily correspond: the patient may be improving cliniclly despite having a worsening appearance on the CXR
  • Ultrasound
    • Can be considered as an alternative to CXR
    • Sensitivity 82% and specificity 94%[3]
  • CBC
  • Chemistry
  • IDSA does not support using initial serum procalcitonin levels to determine whether empiric antibiotics should be initiated. **Clinical judgement plus radiographic evidence alone should guide therapy (strong recommendation, moderate quality of evidence)

If patient will be admitted:

  • Blood Cultures are ONLY indicated for CAP patients with:
    • ICU (required)
    • Multi-lobar
    • Pleural effusion
    • Cavitary lesions
    • Leukopenia
    • Prosthetic valves
    • IV drug users
    • Parenteral antibiotics in the last 90 days
    • Consider for higher-risk patients admitted with CAP
      • Liver disease
      • Immunocompromised
      • Significant comorbidities
      • Other risk factors
  • Sputum staining
    • If concern for particular organism

Chest X-Ray Mimics

  • Legionella urine antigen test
    • ICU patients
    • Alcoholics
    • Outbreaks
    • Recent (within 2 weeks) travel history



Coverage targeted at S. pneumoniae, H. influenzae. M. pneumoniae, C. pneumoniae, and Legionella


No comorbidities (chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia) and no or risk factors for MRSA or Pseudomonas aeruginosa (include prior respiratory isolation of MRSA or P. aeruginosa or recent hospitalization AND receipt of parenteral antibiotics (in the last 90 d))

  • Amoxicillin 1 g three times daily (strong recommendation, moderate quality of evidence), OR
  • Doxycycline 100 mg twice daily (conditional recommendation, low quality of evidence), OR
  • Macrolide in areas with pneumococcal resistance to macrolides <25% (conditional recommendation, moderate quality of evidence).
  • Duration of therapy 5 days minimum


If patient has comorbidities or risk factors for MRSA or Pseudomonas aeruginosa

  • Combination therapy:
    • Amoxicillin/Clavulanate
      • 500 mg/125 mg TID OR amox/clav 875 mg/125 mg BID OR 2,000 mg/125 mg BID. Duration is for a minimum of 5 days and varies based on disease severity and response to therapy; patients should be afebrile for ≥48 hours and clinically stable before therapy is discontinued[6]
    • OR cephalosporin
    • AND macrolide
      • Azithromycin 500 mg on first day then 250 mg daily
      • OR clarithromycin 500 mg BID OR clarithromycin ER 1,000 mg daily]) (strong recommendation, moderate quality of evidence for combination therapy)
    • OR doxycycline 100 mg BID (conditional recommendation, low quality of evidence for combination therapy)
  • Monotherapy: respiratory fluoroquinolone (strong recommendation, moderate quality of evidence):


  • Monotherapy or combination therapy is acceptable
  • Combination therapy includes a cephalosporin and macrolide targeting atypicals and Strep Pneumonia [7]
  • The use of adjunctive corticosteroids (methylprednisolone 0.5 mg/kg IV BID x 5d) in CAP of moderate-high severity (PSI Score IV or V; CURB-65 ≥ 2) is associated with:[8]
    • ↓ mortality (3%)
    • ↓ need for mechanical ventilation (5%)
    • ↓ length of hospital stay (1d)

Community Acquired (Non-ICU)

Coverage against community acquired organisms plus M. catarrhalis, Klebsiella, S. aureus

Hospital Acquired or Ventilator Associated Pneumonia

  • 3-drug regimen recommended options:
  • Consider tobramycin in place of fluoroquinolones given FDA 2016 warnings
  • Of note, the combination of vanco+ piperacillin-tazobactam carries higher risk of AKI when compared to cefepime + vanco’’’[9]

Ventilator Associated Pneumnoia

  • High Risk of MRSA: Use 3-Drug Regimen. Several options are available, but recommendation is to include an antibiotic from each of these categories:[10]
    • 1. MRSA Antibiotic: Vancomycin 15mg/kg q12h OR Linezolid 600 mg IV q12h PLUS
    • 2. Antipseudomonal Antibiotic: Piperacillin-Tazobactam 4.5gm q6h OR Cefepime 2 g IV q8h OR Imipenem 500 mg IV q6h OR Aztreonam 2 g IV q8h PLUS
    • 3. GN Antibiotic With Antipseudomonal Activity: Cipro 400 mg IV q8h

ICU, low risk of pseudomonas

ICU, risk of pseudomonas


IDSA 2019 guidelines recommend clinical judgement plus PSI over CURB-65. [11]

Pneumonia severity index (Port Score)

Risk Factors

Demographic Factors
Age for men
Age for women
Age -10
Nursing home resident
Coexisting Illnesses

Neoplastic disease (active)
Chronic liver disease
Heart Failure
Cerebrovascular disease
Chronic renal disease
Physical Exam

RR > 30/min
Sys BP < 90
Temp <35 or >40
Pulse > 125
Lab and xray findings

Arterial pH < 7.35
BUN > 30
Na <130
Glucose > 250
Hematocrit <30%
PaO2 < 60 or SpO2 < 90%
Pleural effusion


<51 0.1%
51-70 0.6%

Disposition Pathway

  • Classes I and II: consider discharge
  • Class III: discharge verus admit based on clinical judgment
  • Classes IV and V: consider admission


  1. Confusion
  2. bUn > 19 mg/dl
  3. RR > 30
  4. BP < 90 SBP, or < 60 DBP
  5. Age > 65
  • Approximate 30-day mortalities and Tx considerations
    • +1 --> 3%, outpt tx
    • +2 -->7%, inpt, possible outpt
    • +3 --> 14% inpt, possible ICU
    • +4-5 --> 30% ICU


  • Half of patients are still symptomatic at 30 days, with a significant minority of patients experiencing chest pain, malaise or mild dyspnea even 2 to 3 months after treatment
  • In adults with CAP whose symptoms have resolved within 5-7 days, it is not recommended to routinely obtain follow-up chest imaging

See Also


  1. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-e67
  2. Feldman C. Pneumonia in the elderly. Clin Chest Med. 1999;20(3):563-573. doi:10.1016/s0272-5231(05)70236-7
  3. Staub LJ, Mazzali Biscaro RR, Kaszubowski E, Maurici R. Lung Ultrasound for the Emergency Diagnosis of Pneumonia, Acute Heart Failure, and Exacerbations of Chronic Obstructive Pulmonary Disease/Asthma in Adults: A Systematic Review and Meta-analysis. J Emerg Med. 2019;56(1):53-69. doi:10.1016/j.jemermed.2018.09.009
  4. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-e67
  5. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-e67
  6. IDSA. Mandell 2007
  7. Chokshi R, Restrepo MI, Weeratunge N, Frei CR, Anzueto A, Mortensen EM. Monotherapy versus combination antibiotic therapy for patients with bacteremic Streptococcus pneumoniae community-acquired pneumonia. Eur J Clin Microbiol Infect Dis. Jul 2007;26(7):447-51
  8. Siemieniuk RA, Meade MO, Alonso-Coello P, Briel M, Evaniew N, Prasad M, Alexander PE, Fei Y, Vandvik PO, Loeb M, Guyatt GH. Corticosteroid Therapy for Patients Hospitalized With Community-Acquired Pneumonia: A Systematic Review and Meta-analysis. Ann Intern Med. Aug 11, 2015
  9. Luther MK, Timbrook TT, Caffrey AR, Dosa D, Lodise TP, LaPlante KL. Vancomycin Plus Piperacillin-Tazobactam and Acute Kidney Injury in Adults: A Systematic Review and Meta-Analysis. Crit Care Med. 2018;46(1):12-20.
  10. Kalil AC, Metersky ML, Klompas M et al. Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016 Sep 1;63(5):e61-e111.
  11. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America AJRCCM Vol. 200, No. 7, Oct 01, 2019
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