pneumonia%20-%20community-acquired
PNEUMONIA - COMMUNITY-ACQUIRED
Community-Acquired Pneumonia (CAP) is an acute infection of the pulmonary parenchyma accompanied by symptoms of acute illness and abnormal chest findings.
It is a lower respiratory tract infection acquired in the community within 24 hours to <2 weeks or occurring ≤48 hours of hospital admission in patients who do not meet the criteria for healthcare-associated pneumonia.
It occurs at the highest rates in the very young and the very old.
Potentially life-threatening especially in older adults and those with comorbid disease.

Principles of Therapy

  • Antibiotics should be initiated as soon as possible upon the diagnosis of community-acquired pneumonia (CAP)
  • Consider local antimicrobial resistance patterns when choosing an antibiotic
  • Among patients with recent antibiotic exposure, do not use antibiotics in the same class as the patient had been receiving previously
  • In patients with low severity, consider a 5-day single antibiotic course
    • May extend duration if patient is still symptomatic after 3 days of treatment
    • Dual antibiotic therapy and quinolones should be avoided in low-severity patients
  • In patients with moderate-high severity, a 7-10-day antibiotic course is recommended
    • Dual antibiotic therapy (Amoxicillin plus a macrolide) is recommended for patients with moderate severity CAP
    • Dual antibiotic therapy with a beta-lactamase stable beta-lactam plus a macrolide is recommended for high severity CAP patients
  • In patients with high-risk pneumonia, the parenteral route is recommended for all antimicrobial administration because the severity of the condition may result in a low perfusion state
  • Infection with anaerobes should also be considered as possible causative organisms in patients with risk of aspiration
    • Addition of anaerobic antimicrobials to routine CAP therapy should only be initiated if lung abscess or empyema is suspected
  • In patients who tested positive for MRSA or P aeruginosa in the respiratory tract within the prior year, initiation of empiric therapy against MRSA or P aeruginosa is recommended in addition to standard CAP antimicrobials
  • Empiric treatment for MRSA or P aeruginosa should only be started in patients with nonsevere CAP if locally validated risk factors are present
    • May continue treatment on the basis of published risk factors even without local etiological data but should obtain culture results after initiation to confirm the presence of MRSA or P aeruginosa

Pharmacotherapy

Recommended Empiric Antibiotic Therapy
Potential Pathogens
Antibiotic
Outpatient Care - Low-risk
No comorbidities or risk factors for MRSA or P aeruginosa Amoxicillin or
Doxycycline or
A macrolide1 (if with <25% local pneumococcal resistance)
 With comorbid illness  Combination therapy: Amoxicillin/clavulanate or a cephalosporin2 plus a macrolide1 or Doxycycline
Monotherapy: Respiratory fluoroquinolone3
Inpatient Care - Moderate-risk
No comorbidities or risk factors for MRSA or P aeruginosa Beta-lactam4 plus a macrolide1 or respiratory fluoroquinolone (Levofloxacin or Moxifloxacin)
Beta-lactam4 plus Doxycycline
 Prior respiratory isolation of MRSA5,6 Add: Vancomycin or Linezolid 
 Prior respiratory isolation of P aeruginosa5  Add: Piperacillin/tazobactam, Cefepime, Ceftazidime, Imipenem, Meropenem, Aztreonam
Inpatient Care - High-risk (Severe)
No comorbidities or risk factors for MRSA or P aeruginosa Beta-lactam4 plus a macrolide1 or respiratory fluoroquinolone (Levofloxacin or Moxifloxacin)
Beta-lactam4 plus Doxycycline
Prior respiratory isolation of MRSA, recent hospitalization, parenteral antibiotic exposure, and locally validated risk factors Add: Vancomycin or Linezolid 
Prior respiratory isolation of P aeruginosa, recent hospitalization, parenteral antibiotic exposure, and locally validated risk factors Add: Piperacillin/tazobactam, Cefepime, Ceftazidime, Imipenem, Meropenem, Aztreonam
Adapted from the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA) 2019 official clinical practice guideline on the diagnosis and treatment of adults with community-acquired pneumonia.
¹Macrolides: Azithromycin, Clarithromycin; Erythromycin for pregnant patients
²Cephalosporins: Cefpodoxime, Cefuroxime
³Respiratory fluoroquinolones: Gemifloxacin, Levofloxacin, Moxifloxacin 
4Beta-lactams: Ampicillin/sulbactam, Cefotaxime, Ceftriaxone, Ceftaroline 
5May start treatment in patients with other risk factors (recent hospitalization with parenteral antibiotics and locally validated risk factors) only if with positive culture results 
6If with risk factors for MRSA, may add treatment against MRSA if with positive rapid nasal PCR result and obtain cultures


Beta-Lactams

Low-risk Pneumonia

  • High-dose Amoxicillin or Co-amoxiclav is preferred
    • Targets >93% of S pneumoniae
    • Comorbidities or recent antimicrobial therapy increase the likelihood of infection with drug-resistant S pneumonia and enteric Gram-negative bacteria which may be treated using a combination of a beta-lactam and a macrolide
  • 2nd-3rd generation cephalosporins can be used as an alternative antibiotic therapy for patients with stable co-morbid conditions
  • Less active in vitro than high-dose Amoxicillin

Moderate-risk and High-risk Pneumonia

  • Parenteral nonpseudomonal beta-lactams with or without a beta-lactamase inhibitor are recommended; some antibiotics from this class may also have anaerobic activity
    • May be given with either an extended macrolide or a respiratory quinolone
  • Recommended beta-lactams include penicillins, 2nd- and 3rd-generation cephalosporins and carbapenems if with P aeruginosa
    risk
  • Combining nonpseudomonal beta-lactams with macrolides results in a significant reduction in mortality
  • Oxacillin
    • Consider giving to patients shown or suspected to have lung abscesses, pneumatoceles or pyothorax, in which Staphylococcus sp is a common etiologic organism
    • The best indicator of S aureus infection is the presence of Gram-positive cocci in clusters in a tracheal aspirate or in an adequate sputum sample

Clindamycin or Beta-lactam/Beta-lactamase Inhibitor

  • May consider adding empiric antibiotic agents Clindamycin or β-lactam/β-lactamase inhibitors in hospitalized patients with suspected aspiration pneumonia if lung abscess or empyema is suspected

Lefamulin

  • A newly-approved pleuromutilin antibiotic that may be used as treatment for community-acquired bacterial pneumonia
  • Studies showed that use of Lefamulin in hospitalized adult patients is non-inferior to Moxifloxacin

Macrolides

Low-risk Pneumonia

  • Macrolides and azalides may be better for patients with extrapulmonary physical findings, a feature of pneumonia caused by atypical pathogens
    • Macrolides may be considered if with <25% local pneumococcal resistance
  • Alternative for patients who are hypersensitive to Penicillin
  • Erythromycin is less active against H influenzae
  • Azithromycin is preferred for outpatients with comorbidities (eg COPD) because of H influenzae

Moderate-risk and High-risk Pneumonia

  • Combining macrolides with nonpseudomonal beta-lactams results in reduced mortality
  • Adding a macrolide to the antibiotic regimen benefits patients in areas with a high prevalence of Legionella sp

Quinolones with Anti-Pneumococcal Action (Respiratory Quinolones)

Low-risk Pneumonia

  • May be used alone as an alternative regimen to combination therapy of beta-lactam with or without beta-lactamase inhibitor plus a macrolide in patients with comorbid illness

Moderate-risk to High-risk Pneumonia

  • Alternative regimen to macrolides in the combination therapy with nonpseudomonal beta-lactam with or without beta-lactamase inhibitor, for patients without comorbid illnesses but with documented allergies, contraindication,or those unresponsive to macrolides
  • In areas with high prevalence of pulmonary tuberculosis (TB), they are better reserved as potential 2nd-line agents for the treatment of multidrug-resistant TB
    • Quinolones may mask the clinical features of pulmonary TB and delay its diagnosis

Tetracyclines
Low-risk and Moderate-risk Pneumonia

  • Doxycycline may be used in low-risk patients and in moderate-risk patients without comorbidities and with documented allergies, contraindication, or those unresponsive to treatment with macrolides and fluoroquinolones
Moderate-risk Pneumonia
  • Omadacycline is a newly-approved broad spectrum antibiotic treatment option for adults with nonsevere CAP especially in the setting of tetracycline resistance with efficacy comparable to Moxifloxacin

Other Treatments

  • Anti-influenza treatment (eg Oseltamivir) is recommended for patients positive for influenza virus regardless of site of care

Duration of Treatment Based on Etiology

Low-risk Pneumonia

  • Minimum of 5 days; usual duration is 5-7 days for most pneumonias of bacterial etiology
  • A 3-day course of oral therapy may be possible with azalides

Moderate-risk And High-risk Pneumonia

Etiologic Agent Duration of Therapy
  • Most bacterial pneumonias except enteric Gram-negative pathogens (MRSA and MSSA), and P aeruginosa
5-7 days; 3-5 days (azalides) for S pneumoniae
  • Enteric Gram-positive pathogens, S aureus (MRSA and MSSA) and P aeruginosa

MSSA CAP

  • Non-bacteremic - 7-14 days
  • Bacteremic - longer up to 21 days

MRSA CAP

  • Non-bacteremic -  7-21 days
  • Bacteremic - longer up to 28 days

P aeruginosa

  • Non-bacteremic - 14-21 days
  • Bacteremic - longer; up to 28 days
  • Mycoplasma sp and Chlamydophila sp
10-14 days
  • Legionella sp
14-21 days; 10 days (azalides)

Pathogen-specific Antimicrobial Therapy

  • S pneumoniae: Penicillin G, Amoxicillin; Alternative: Macrolide, 2nd-3rd generation cephalosporin
  • H influenzae: Amoxicillin, 2nd-3rd generation cephalosporin, Amoxicillin-clavulanate; Alternative: Fluoroquinolone
  • M pneumoniae/C pneumoniae: Macrolide, tetracycline; Alternative: Fluoroquinolone
  • Legionalla sp: Fluoroquinolone, Macrolide (Clarithromycin, Azithromycin)
  • Chlamydophila psittaci, Coxiella burnetti: Tetracycline; Alternative: Macrolide
  • P aeruginosa: Antipseudomonal beta-lactam plus (Ciprofloxacin or Levofloxacin or aminoglycoside)
  • Acinetobacter sp: Carbapenem
  • S aureus: Antistaphylococcal penicillin if methicillin-susceptible; Vancomycin or Linezolid if methicillin-resistant
  • Enterobacteriaceae: Extended-spectrum beta-lactamase producer (3rd generation cephalosporin, carbapenem)

Supportive Therapy

Outpatient Care

  • Analgesics may help relieve pleuritic pain

Inpatient Care

  • Oxygen therapy should be given to reach PaO2 of ≥8 kPa and SpO2 94-98%
  • IV fluids and nutritional support should be provided
  • Mobility should be encouraged in patients with uncomplicated CAP
  • Consider airway clearance techniques in patients with sputum and difficulty in expectoration, or if with preexisting respiratory disease
Digital Edition
Asia's trusted medical magazine for healthcare professionals. Get your MIMS Respirology - Malaysia digital copy today!
Sign In To Download
Editor's Recommendations
Most Read Articles
Stephen Padilla, 16 Oct 2019
Treatment without antibiotic medication does not appear to be inferior to moxifloxacin therapy as regards treatment failure or length of stay (LOS) among patients with chronic obstructive pulmonary disease (COPD) requiring hospitalization for nonpurulent exacerbation, according to the results of a study presented at the European Respiratory Society (ERS) International Congress 2019.
Roshini Claire Anthony, 16 Oct 2019

Antibiotic prophylaxis with azithromycin in individuals with primary antibody deficiencies (PAD) may lead to a reduced risk of respiratory exacerbations, according to a phase II trial presented at ERS 2019.

Pearl Toh, 14 Oct 2019
About one-third of patients with severe asthma who are on high-dose inhaled corticosteroids (ICS) are also receiving excessive doses of oral corticosteroids (OCS), reveals a study presented at the ERS 2019 Meeting.
Tristan Manalac, 11 Sep 2018
The immediate reduction of cigarette nicotine content results in greater improvements in levels of smoke exposure biomarkers than gradual reduction, though withdrawal symptoms are stronger, according to a recent study.