Infection severity

Probable pathogen(s)

Antibiotic agent

Comments

Mild (usually treated with oral agent[s])

Staphylococcus aureus (MSSA); Streptococcus spp.

Dicloxacillin

Requires QID dosing; narrow-spectrum; inexpensive

Clindamycinb

Usually active against community-associated MRSA, but check macrolide sensitivity and consider ordering a “D-test” before using for MRSA. Inhibits protein synthesis of some bacterial toxins

Cephalexin ^b

Requires QID dosing; inexpensive

Levofloxacin^b

Once-daily dosing; suboptimal against S. aureus

Amoxicillin-clavulanate ^b

Relatively broad-spectrum oral agent that includes anaerobic coverage

Methicillin-resistant S. aureus (MRSA)

Doxycycline

Active against many MRSA & some gram-negatives; uncertain against streptococcus species

Trimethoprim/sulfamethoxazole

Active against many MRSA & some gram-negatives; uncertain activity against streptococci

Moderate (may be treated with oral or initial parenteral agent[s]) or severe (usually treated with parenteral agent[s])

MSSA; Streptococcus spp.; Enterobacteriaceae; obligate anaerobes

Levofloxacinb

Once-daily dosing; suboptimal against S. aureus

Cefoxitinb

Second-generation cephalosporin with anaerobic coverage

Ceftriaxone

Once-daily dosing, third-generation cephalosporin

Ampicillin-sulbactam ^b

Adequate if low suspicion of P. aeruginosa

Moxifloxacin^b

Once-daily oral dosing. Relatively broad-spectrum, including most obligate anaerobic organisms

Ertapenem ^b

Once-daily dosing. Relatively broad-spectrum including anaerobes, but not active against P. aeruginosa

Tigecycline^b

Active against MRSA. Spectrum may be excessively broad. High rates of nausea and vomiting and increased mortality warning. Nonequivalent to ertapenem + vancomycin in one randomized clinical trial

Levofloxacinb or ciprofloxacin^b with clindamycin^b

Limited evidence supporting clindamycin for severe S. aureus infections; PO & IV formulations for both drugs

Imipenem-cilastatin ^b

Very broad-spectrum (but not against MRSA); use only when this is required. Consider when ESBL-producing pathogens suspected

MRSA

Linezolid^b

Expensive; increased risk of toxicities when used >2 weeks

Daptomycin^b

Once-daily dosing. Requires serial monitoring of CPK

Vancomycin ^b

Vancomycin MICs for MRSA are gradually increasing

Pseudomonas aeruginosa

Piperacillin-tazobactam ^b