What antibiotic is recommended for a scratch that has become infected?

Antibiotic Treatment for an Infected Scratch

For a simple infected scratch, amoxicillin-clavulanate 875/125 mg twice daily for 5-7 days is the first-line treatment, providing optimal coverage against the polymicrobial flora typically found in skin infections including Staphylococcus, Streptococcus, and anaerobes. 1

First-Line Therapy

• Amoxicillin-clavulanate (Augmentin) 875/125 mg orally twice daily is the preferred antibiotic for infected scratches, offering broad-spectrum coverage against the most common pathogens 1
• Treatment duration should be 5-7 days for uncomplicated soft tissue infections, with extension only if infection has not improved within this timeframe 1
• This regimen covers methicillin-susceptible Staphylococcus aureus (MSSA), Streptococcus species, and anaerobes that commonly cause wound infections 1

When to Consider Alternative Antibiotics

For Penicillin Allergy:

• Doxycycline 100 mg orally twice daily is an excellent alternative, though some streptococci may be resistant 1, 2
• Clindamycin 300-450 mg orally three times daily provides good coverage against staphylococci, streptococci, and anaerobes 1
• Trimethoprim-sulfamethoxazole (TMP-SMZ) 1-2 double-strength tablets twice daily can be used but has poor anaerobic coverage and should be combined with metronidazole if anaerobes are suspected 1

If MRSA is Suspected:

Look for these risk factors: penetrating trauma, evidence of MRSA infection elsewhere, nasal MRSA colonization, injection drug use, or systemic inflammatory response syndrome (SIRS) 1

• TMP-SMZ 1-2 double-strength tablets twice daily provides MRSA coverage 1
• Doxycycline 100 mg twice daily has activity against community-acquired MRSA 1, 2
• Clindamycin 300-450 mg three times daily is effective if local MRSA resistance rates are <10% 1

Critical Antibiotics to AVOID

• First-generation cephalosporins (cephalexin, cefazolin) should NOT be used as monotherapy for scratches from animals or contaminated sources, as they miss Pasteurella multocida and anaerobes 1, 3
• Penicillinase-resistant penicillins (dicloxacillin, nafcillin) alone are inadequate for polymicrobial wound infections 1, 3

When to Escalate to IV Therapy

For severe infections with systemic signs (fever, lymphangitis, significant cellulitis spreading beyond the immediate wound area):

• Ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours is first-line for hospitalized patients 1, 3
• Vancomycin 15-20 mg/kg IV every 8-12 hours should be added if MRSA is strongly suspected or confirmed 1
• Piperacillin-tazobactam 3.37 g IV every 6-8 hours is an alternative for severe polymicrobial infections 1, 3

Special Circumstances Requiring Attention

Cat Scratches Specifically:

• If the scratch is from a cat, maintain the same first-line therapy (amoxicillin-clavulanate), as it covers Pasteurella multocida, which is present in 50-80% of cat mouths 3, 4
• Consider azithromycin 500 mg day 1, then 250 mg daily for 4 days if cat scratch disease (Bartonella henselae) is suspected, characterized by regional lymphadenopathy developing 1-3 weeks after the scratch 1

Hand or Finger Infections:

• These carry the highest risk for complications including septic arthritis, osteomyelitis, and tendonitis 3, 4
• If there is any concern for deep space infection, abscess, or lack of improvement within 48 hours, surgical consultation for incision and drainage is mandatory in addition to antibiotics 3, 4

High-Risk Patients:

For immunocompromised patients, diabetics, or those with peripheral vascular disease:

• Consider broader empiric coverage with vancomycin plus piperacillin-tazobactam or a carbapenem for severe infections 1
• Extend treatment duration to 1-2 weeks minimum, potentially up to 3-4 weeks if resolution is slow 4
• Ensure optimal wound care including debridement of any necrotic tissue 4

Common Pitfalls to Avoid

• Do not use fluoroquinolones (ciprofloxacin, levofloxacin) as first-line therapy unless penicillin-allergic, as they miss MRSA and some anaerobes 1
• Do not rely on cephalexin alone for contaminated wounds or animal scratches, despite its effectiveness for simple staphylococcal/streptococcal infections 1, 5
• Do not delay surgical evaluation for hand infections, deep wounds, or signs of abscess formation 3, 4
• Ensure tetanus immunization is current: give booster if >5 years for dirty wounds or >10 years for clean wounds 1

Monitoring and Follow-Up

• Patients should return immediately if signs worsen: increasing pain, redness, swelling, purulent drainage, fever, or red streaking (lymphangitis) 4
• Re-evaluate within 48-72 hours if not improving on initial therapy 1, 4
• Consider culture and sensitivity testing if infection fails to respond to empiric therapy or if MRSA is suspected 1