Pneumonia, Community-acquired (CAP)

[Am J Respir Crit Care Med 2019;200: e45-67, NICE guideline]

 

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Pathogens

- Viruses are the most common pathogen found in CAP patients, including those hospitalized with CAP.

- S. pneumoniae most common bacterial pathogen causing CAP and must be covered with initial empiric antibiotic therapy.

- Atypical pathogens (Chlamydophila pneumoniae/Mycoplasma pneumoniae/Legionella spp) 15% of CAP but do not need to be empirically covered in all patients.

 

Antibiotic therapy

- Amoxicillin:

  • provides the best coverage of all oral β-lactams against S. pneumoniae, even majority of penicillin-resistant strains.

  • no activity against S. aureus, β-lactamase (+) H. influenzae, M. catarrhalis, M. pneumoniae, C. pneumoniae, or Legionella spp.

- Doxycycline:

  • excellent activity against most CAP pathogens, including S. pneumoniae (increasing resistance), H. influenzae, M. catarrhalis, S. aureus, including MRSA, M. pneumoniae, C. pneumoniae, and Legionella spp.

  • not associated with promoting penicillin resistance in S. pneumoniae (macrolides have)

  • excellent pharmacokinetics/dynamics (high serum and lung levels, concentration-dependent killing).

- Macrolides:

  • significant macrolide resistance in S. pneumoniae.

  • poor Haemophilus coverage.

  • recent (within previous 3 months) macrolide use may predispose to infection with multi-drug resistant S. pneumoniae.

  • monotherapy with macrolides not recommended for pneumococcal bacteremia (clinical history of rigors/positive blood cultures).

- Quinolones:

  • assess risk vs. benefit of using a quinolone in light of serious adverse effect profile (Health Canada summary safety review)

  • recent (within previous 3 months) quinolone use may predispose to infection with quinolone resistant S. pneumoniae.

  • therapy in patients with undiagnosed tuberculosis may result in false negative Mycobacterium tuberculosis cultures.

  • Moxifloxacin not listed as:

    • anaerobic coverage not required for CAP

    • increased risk of Clostridioides difficile infection compared to levofloxacin [CMAJ 2008; 179:767-72]

- The following antibiotics are not recommended empirically in adult community-acquired pneumonia:

  • cephalexin/cefazolin - no activity against Pen I/R S. pneumoniae, Haemophilus spp, M. pneumoniae, C. pneumoniae, or Legionella spp.

  • cefixime - no activity against pen I/R S. pneumoniae, M. pneumoniae, C. pneumoniae, or Legionella spp.

  • ciprofloxacin – poor/no activity against S. pneumoniae

  • TMP/SMX - increased S. pneumoniae resistance; no activity against M. pneumoniae, C. pneumoniae, or Legionella spp.

- Other considerations:

  • Gastric acid suppressants and inhaled corticosteroids are associated with an increased risk of CAP.

  • The following measures are recommended: