Pneumonia, Community-acquired (CAP)
[Am J Respir Crit Care Med 2019;200: e45-67, NICE guideline]
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 (Chlamydia 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)
- lower risk of C. difficile infection (CDI) compared to azithromycin, especially in patients with a prior history of CDI [Am J Infect Control 2024;52:280-3].
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.
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The following measures are recommended:
smoking cessation
pneumococcal vaccine where indicated.