Antibiotic Treatment for Laceration-Related Bacterial Infections
Primary Recommendation
For a simple laceration with suspected bacterial infection, oral cephalexin (500 mg every 6 hours) or amoxicillin-clavulanate (500-875 mg twice daily) should be initiated as first-line therapy for 5-7 days. 1, 2
Treatment Algorithm Based on Wound Characteristics
Clean, Simple Lacerations (No Contamination)
First-line options:
These agents target the most common pathogens: Staphylococcus aureus and beta-hemolytic streptococci 1
Duration: 5 days if clinical improvement occurs; extend if no improvement 2
Contaminated Lacerations or Bite Wounds
Amoxicillin-clavulanate is the antibiotic of choice for contaminated wounds and all bite wounds (animal or human). 1, 2
Oral dosing: 500-875 mg twice daily or 500 mg three times daily 1, 2
IV alternative (if hospitalized): Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
This provides essential coverage against:
Fresh Water Contamination
If the laceration occurred in fresh water, avoid first-generation cephalosporins and use fluoroquinolones or third-generation cephalosporins. 1, 3
Recommended regimens:
This covers Aeromonas hydrophila, which is resistant to commonly used oral cephalosporins and can cause rapidly progressive infection 3
Soil Contamination with Tissue Damage
Add penicillin or metronidazole to the cephalosporin regimen to cover Clostridium species. 1
- Regimen: First-generation cephalosporin PLUS penicillin 1
- Alternative: Amoxicillin-clavulanate alone provides adequate anaerobic coverage 1
MRSA Considerations
When to Suspect MRSA
Add MRSA coverage if any of the following are present: 1, 2
- Purulent drainage from the wound 1
- Penetrating trauma or injection drug use 2
- Known MRSA colonization 2
- Failure to respond to beta-lactam therapy after 48-72 hours 1
MRSA-Active Oral Options
If MRSA is suspected, switch to or add one of the following: 1, 2
- Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets twice daily 1, 2
- Doxycycline: 100 mg twice daily 1, 2
- Clindamycin: 300-450 mg four times daily 1, 2, 4
Important caveat: If dual coverage for both streptococci and MRSA is needed, use clindamycin alone OR combine TMP-SMX or doxycycline with amoxicillin. 1
Indications for IV Therapy and Hospitalization
Hospitalize and initiate IV antibiotics if any of the following are present: 1, 2
- Systemic inflammatory response syndrome (fever, tachycardia, leukocytosis) 1, 2
- Hemodynamic instability 1, 2
- Altered mental status 1, 2
- Concern for necrotizing infection (severe pain out of proportion, crepitus, skin necrosis) 1, 2
- Severe immunocompromise 1, 2
IV Regimens for Severe Infections
For complicated skin and soft tissue infections requiring hospitalization: 1, 2
- MRSA coverage: Vancomycin 15-20 mg/kg every 8-12 hours 1, 2
- Broad-spectrum coverage: Add piperacillin-tazobactam 3.37 g every 6-8 hours OR a carbapenem 1, 2
- If streptococcal/MSSA only: Cefazolin 1 g every 8 hours 1, 2
Duration: 7-14 days based on clinical response 1
Critical Pitfalls to Avoid
- Never use first-generation cephalosporins alone for fresh water injuries – they miss Aeromonas 3
- Never use TMP-SMX or doxycycline as monotherapy for non-purulent cellulitis – they lack adequate streptococcal coverage 1
- Never use fluoroquinolones for MRSA infections – they are inadequate 1
- Avoid vancomycin if renal impairment exists or MRSA MIC ≥1.5 mg/mL – use daptomycin or linezolid instead 1
- Do not delay antibiotics beyond 3 hours in open fractures or severe contamination – infection risk increases significantly 1