Community-Acquired Pneumonia (CAP)

Choice of Antimicrobials

Indication for Therapy	Usual Causative Organisms	Antimicrobials Regimens
Outpatient treatment Individual with comorbidities (chronic heart, lung, liver or renal disease, diabetes, alcoholism, malignancies, asplenia) Individuals with immunosuppressive disease or on immunosuppressant therapy Use of antibiotics in last 3 months (consider selecting an antibiotic from a different class as previous exposure to antibiotics within this timeframe is a risk factor for developing drug-resistant Streptococcus pneumoniae)	S. pneumoniae, M. pneumoniae, C. pneumoniae, H. influenzae, M. catarrhalis Legionella spp., Enterobacterales	amoxicillin/clavulanate 875/125 mg PO q12h +/- azithromycin 500 mg PO day 1, then 250 mg PO daily x 4 days^* OR amoxicillin/clavulanate 875/125 mg PO q12h +/- doxycycline 100 mg PO q12h x 7 days^*
		β-lactam allergy (anaphylaxis): moxifloxacin 400 mg PO q24h
Inpatient admission (non-ICU)	S. pneumoniae, M. pneumoniae, C. pneumoniae, H. influenzae, Legionella spp.	cefTRIAXone 1 g IV q24h +/- azithromycin 500 mg IV/PO day 1, then 250-500 mg IV/PO q24h x 4 days^* OR cefTRIAXone 1 g IV q24h +/- doxycycline 100 mg PO q12h x 7 days^*
		β-lactam allergy (anaphylaxis): moxifloxacin 400 mg IV/PO q24h
		Options for oral step-down therapy from cefTRIAXone includes one of: amoxicillin/clavulanate 875/125 mg PO q12h OR cefuroxime 500 mg PO q12h
Inpatient ICU admission Always provide atypical coverage	S. pneumoniae, S. aureus, Legionella spp., Gram-negative bacilli, H. influenzae	cefTRIAXone 1 g IV q24h + azithromycin 500 mg IV q24h
Inpatient ICU admission Always provide atypical coverage		β-lactam allergy (anaphylaxis): moxifloxacin 400 mg IV q24h
Influenza suspected	Influenza A or B	Add oseltamavir 75 mg PO q12h x 5 days
Macroaspiration suspected	Oral anaerobes	cefTRIAXone 1g IV q24h (CTX has adequate oral anaerobic coverage and may be used alone). In the setting of severe anaerobic pulmonary infection (e.g. lung abscess, empyema): metroNIDAZOLE 500 mg IV/PO q12h may be added.
Macroaspiration suspected	Oral anaerobes	amoxicillin/clavulanate 875/125 mg PO q12h
MRSA suspected	Methicillin-resistant Staphylococcus aureus	Add vancomycin 15 mg/kg IV q12h (Dose as per hospital guidelines)
Pseudomonas suspected	Pseudomonas aeruginosa	Refer to Hospital Acquired Pneumonia Guidelines

^* Consider adding atypical coverage when “enhanced surveillance directive” from Public Health has been issued or when patients have not responded to drug therapy after 48 hours.

If the patient has received antibiotics within the last 3 months, consideration should be given to prescribing an agent from a different class.

Duration of Therapy

Minimum of 3 days. Patients should be afebrile for 48h and clinically stable before discontinuation of therapy.

References

Mandell LA et al. Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults. Clin Infect Dis. 2007;44:S27-72.
Ruhe JJ and Hasbun R. Streptococcus pneumoniae Bacteremia: Duration and Previous Antibiotic Use and Association with Penicillin Resistance. Clin Infect Dis. 2003;36:1132-38.
Leroy O, Saux P, Bedos JP, Caulin E. Comparison of Levofloxacin and Cefotaxime Combined With Ofloxacin for ICU Patients With Community-Acquired Pneumonia Who Do Not Require Vasopressors. CHEST. 2005;128:172-83.
Doernberg SB, Winston LG, Deck DH, Chambers HF. Does doxycycline protect against development of Clostridium difficile Infection? Clin Infect Dis. 2012:55:615-620.
El Moussaoui R, De Borgie CAMJ, Van Den Broek P, et al. (2006). Effectiveness of discontinuing antibiotic treatment after three days versus eight days in mild to moderate-severe community acquired pneumonia: randomised, double blind study. BMJ. 332(7554):1355.