Infection Type

Most Common Organism

Other Considerations

Initial Antibiotic Therapy

Cellulitis

Staphylococcus Streptococcus

Antibiotic synergy for streptococcal infections with clindamycin

First-generation cephalosporin or penicillin (Streptococcus only)

Abscess (e.g., paronychia, felon, deep space infections)

Staphylococcus aureus

MRSA is common now in the community; start therapy for MRSA empirically and change to nafcillin or first-generation cephalosporin if methicillin sensitive

IV: Vancomycin or clindamycin for inpatients Linezolid or tigecycline if unable to tolerate

vancomycin

Oral: Trimethoprim/sulfamethoxazole (Bactrim), clindamycin or doxycycline

Flexor

tenosynovitis

Staphylococcus aureus, anaerobes

Polymicrobial infections have worse prognosis. Consider multimodal therapy as initial treatment until culture results are back, especially in immunocompromised  patients

IV: Ampicillin/sulbactam (Unasyn) plus cefoxitin (second-generation cephalosporin)

Oral: Amoxicillin/clavulanate (Augmentin)

If penicillin allergic: fluoroquinolone (Cipro or other)

plus clindamycin

Pyarthrosis

Staphylococcus

Requires parenteral therapy MRSA is common now in the

community; start therapy for MRSA empirically and change to nafcillin or first-generation cephalosporin if

methicillin-sensitive

Consider coverage for Neisseria gonorrhoeae in sexually active patients

IV: Vancomycin

Add ceftriaxone for N. gonorrhoeae coverage Presumptive treatment for MRSA until cultures are

back, then change to antibiotic appropriate to organism with the least side-effect profile

Human bite

Staphylococcus Streptococcus Eikenella corrodens Anaerobes

IV: Ampicillin/sulbactam (Unasyn) plus cefoxitin

Oral: Amoxicillin/clavulanate (Augmentin)

If penicillin allergic: fluoroquinolone (Cipro) plus

clindamycin

Alternative: Third-generation cephalosporin plus anerobic coverage with clindamycin or metronidazole (Flagyl)

Note: Quinolones not indicated in children

Animal bites

Pasteurella multocida Staphylococcus Streptococcus

IV: Ampicillin/sulbactam (Unasyn) plus cefoxitin

Oral: Amoxicillin/clavulanate (Augmentin)

If penicillin allergic: fluoroquinolone plus clindamycin

Alternative: Third-generation cephalosporin plus anaerobic coverage with clindamycin or metronidazole (Flagyl)

Note: quinolones not indicated in children

Suspected MRSA–CA

Suspected based on clinical appearance and relative frequency of MRSA-CA seen in one’s community

IV: Vancomycin or clindamycin

Oral: Trimethoprim/sulfamethoxazole (Bactrim), clindamycin

Suspected MRSA–HA

IV: Vancomycin or linezolid or daptomycin

Necrotizing fasciitis

Streptococcus or Polymicrobial

Treat both until organism is identified

Broad-spectrum beta-lactam (piperacillin/tazobactam; imipenem) plus vancomycin (for MRSA) plus clindamycin (for synergy for Streptococcus pyogenes)

Gas in soft tissues

Clostridium perfringens (gas gangrene)

Polymicrobial infections (anaerobic and

facultative anaerobes)

IVDA and diabetics more often have polymicrobial infections—often gas in the soft tissues

High-dose penicillin plus clindamycin

Broad-spectrum beta-lactam (piperacillin/tazobactam; imipenem) plus vancomycin (for MRSA) plus clindamycin (for synergy for S. pyogenes)

IVDA, Intravenous drug abusers; MRSA, methicillin-resistant Staphylococcus aureus; MRSA-CA, community-acquired MRSA; MRSA-HA, hospital-acquired MRSA.