Antibiotic Therapy for Bacterial Community-Acquired Pneumonia in Adults 

I. Outpatients—no comorbidities or risk factors for MRSA and Pseudomonas aeruginosa present*

Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Haemophilus influenzae, respiratory viruses, miscellaneous organisms (eg, Legionella, Mycobacterium tuberculosis, endemic fungi)

Amoxicillin

plus either

Macrolide (azithromycin or clarithromycin)

or

Doxycycline (if allergic to macrolides)

II. Outpatients—comorbidities present*

S. pneumoniae, including antibiotic-resistant forms; M. pneumoniae; C. pneumoniae; mixed infection (bacteria + atypical pathogen or virus); H. influenzae; enteric gram-negative organisms; respiratory viruses; miscellaneous organisms (eg, Moraxella catarrhalis, Legionella, anaerobes [aspiration], M. tuberculosis, endemic fungi)

Beta-lactam (cefpodoxime, cefuroxime, amoxicillin, or amoxicillin/clavulanic acid)

plus either

Macrolide or doxycycline

or

Monotherapy with antipneumococcal fluoroquinolone (eg, moxifloxacin, levofloxacin)

III. Inpatient—not in intensive care unit (ICU), no risk factors for MRSA or P. aeruginosa

S. pneumoniae, H. influenzae, M. pneumoniae, C. pneumoniae, mixed infection (bacteria + atypical pathogen or virus), respiratory viruses, Legionella, miscellaneous organisms (eg, M. tuberculosis, endemic fungi, Pneumocystis jirovecii)

Azithromycin

plus

Beta-lactam (eg, cefotaxime, ceftriaxone, ceftaroline)

or

Antipneumococcal fluoroquinolone orally or intravenously (alone)

IVA. ICU patient—no risk factors for MRSA or P. aeruginosa

S. pneumoniae, including antibiotic-resistant forms; Legionella; H. influenzae; enteric gram-negative organisms; Staphylococcus aureus; M. pneumoniae; respiratory viruses; miscellaneous organisms (eg, C. pneumoniae, M. tuberculosis, endemic fungi)

Beta-lactam (cefotaxime or ceftriaxone)

plus either

Antipneumococcal fluoroquinolone

or

Azithromycin

IVB. Inpatient or ICU patient—MRSA or Pseudomonas risk factors present (if prior isolation is the only risk factor, add initial coverage for that pathogen only and obtain cultures)

Same as those for category IVA (above) plus MRSA or Pseudomonas

Linezolid or vancomycin

or/plus

Antipseudomonal beta-lactam (cefepime, ceftazidime, imipenem, meropenem, piperacillin/tazobactam) or aztreonam (if allergic to or intolerant of beta-lactams)