Community-acquired Pneumonia

These materials are intended for general clinical education and guidance. They are not a substitute for a clinician’s knowledge, skill or judgment in treating patients.

Background

Pneumonia is a heterogeneous infection caused by viruses, bacteria and occasionally fungi, although the pathogen is unknown in the majority of clinical cases. Mortality risk can be assessed using the CRB-65 or PSI score, which helps define management location and choice of antimicrobial. Infectious disease and/or respirology consultations should be considered for patients with no improvement or worsening symptoms after three days of therapy.

Initial assessment

Clinical symptoms such as cough, pleuritic chest pain and dyspnea, along with clinical signs including fever, tachycardia, tachypnea and hypoxemia, should prompt an X-ray to confirm the diagnosis. Sputum and blood cultures are recommended only for patients who are severely or critically ill.

Common pathogens

• Respiratory viruses, including influenza, parainfluenza, adenovirus, coronavirus and human metapneumovirus
• S. pneumoniae (the most common bacterial cause)
• H. influenzae (uncommon but possible in patients with a smoking history or structural lung disease)
• M. pneumoniae
• C. pneumoniae

Empiric therapy (first-line)

Patients without any of the following: recent amoxicillin use (within the past 1-3 months), lung disease, immunocompromise, smoking history, or moderate to severe illness (CRB 0-1):

• Amoxicillin 1 g PO TID

OR

• Ampicillin 1 g IV q6h

Patients with any of the following: recent amoxicillin use (within the past 1-3 months), structural lung disease, immunocompromise, smoking history, or moderate to severe illness (CRB ≥ 2, hypoxemia):

• Amoxicillin/clavulanate 875/125 mg PO BID

OR

• Ceftriaxone 1 g IV q24h (consider ceftriaxone 2g IV q24h if critically ill)

And consider:

• Azithromycin 500 mg IV/PO daily
  • Note: Legionella risk in Ontario is highest from June to November

Alternative for allergy to first-line regimen

Patients without any of the following: lung disease, immunocompromise, smoking history, or moderate to severe illness (CRB 0-1):

• Doxycycline 100 mg PO BID

Patients with any of the following: lung disease, immunocompromise, smoking history, or moderate to severe illness (CRB ≥ 2, hypoxemia):

• Levofloxacin 750 mg PO/IV q24h
  • Use moxifloxacin 400 mg IV/PO q24h if levofloxacin is not available

Duration of treatment

• Three days: For patients who are afebrile and clinically stable (not tachycardic, tachypnic or hypoxemic) on day 3.
  • Note: Three-day duration supported by an RCT by Dinh et al. Patients with ICU admission, immunocompromise, or complications were excluded.²
• Five days: For patients who are afebrile for 48 hours but do not meet the three-day criteria.
• Seven days: For the minority of patients who remain febrile on or after day 3, improve slowly, are severely immunocompromised, or have bacteremia.

Clinical pearls

• Reassess duration daily using the stability criteria above
• Changing from IV to PO therapy has been associated with a shorter length of stay
• When calculating total treatment days, include outpatient, emergency department and inpatient antimicrobial use; the majority of patients receive more than necessary
• Cough, fatigue, and chest X-ray changes may take days to weeks to improve and do not require ongoing antimicrobial therapy
• “Atypical” pathogens are unlikely causes of non-severe CAP in adults who require hospitalization