What is the treatment for a bacterial infection on the side of the nail and down the finger, likely caused by Staphylococcus aureus or Streptococcus pyogenes?

Treatment of Bacterial Infection on the Side of the Nail and Down the Finger

For a bacterial infection involving the nail fold (paronychia) extending down the finger, you should initiate oral antibiotics effective against both Staphylococcus aureus and Streptococcus pyogenes, specifically a penicillinase-resistant semisynthetic penicillin or first-generation cephalosporin, combined with incision and drainage if an abscess is present. 1

Initial Assessment and Management Approach

Determine if Abscess is Present

• If a discrete abscess or fluctuance is present: Incision and drainage is the primary treatment and must be performed first 1
• If diffuse cellulitis without abscess: Antibiotics alone are appropriate 1
• The infection you describe (starting at the nail fold and extending down the finger) suggests acute paronychia with possible extension to cellulitis 2

Antibiotic Selection Strategy

For mild to moderate infection (outpatient management):

• First-line oral therapy: A penicillinase-resistant semisynthetic penicillin (such as dicloxacillin) or first-generation cephalosporin (such as cephalexin) to cover both S. aureus and S. pyogenes 1
• Alternative if penicillin-allergic: Clindamycin 600 mg three times daily, noting that 99.5% of S. pyogenes strains remain susceptible to clindamycin 1
• Duration: 7-14 days depending on clinical response 1

For severe infection or failure to respond to initial therapy:

• Assume MRSA given high community prevalence and initiate MRSA-active therapy 1
• Inpatient IV options: Vancomycin, linezolid 600 mg twice daily, or daptomycin 4 mg/kg/dose once daily 1
• Outpatient oral MRSA coverage: Trimethoprim-sulfamethoxazole or doxycycline/minocycline, though you must reevaluate the patient in 24-48 hours as treatment failure rates of 21% have been reported with tetracyclines 1

Critical Clinical Pitfalls to Avoid

Do Not Miss an Abscess

• Palpate carefully for fluctuance - if present, antibiotics alone will fail and drainage is mandatory 1
• Simple warm soaks with or without Burow solution or 1% acetic acid may be sufficient for very early paronychia without abscess 2

Consider MRSA Risk Factors

• Empiric MRSA coverage is warranted if: Patient has failed initial beta-lactam therapy, has known MRSA colonization, or lives in an area with high CA-MRSA prevalence 1
• Community-acquired MRSA is increasingly common in skin infections 1

Recognize When Infection is More Serious

• Red flags for deeper infection: Severe pain out of proportion to exam findings, rapid progression, systemic symptoms (fever, hypotension), or signs suggesting necrotizing fasciitis 1
• If cellulitis is progressing despite antibiotics, this may indicate resistant organisms or a deeper/more serious infection than initially recognized 1

Topical Therapy Considerations

Topical antibiotics are generally insufficient for paronychia with extension down the finger 1

• Mupirocin 2% ointment is FDA-approved for impetigo caused by S. aureus and S. pyogenes but is not adequate for infections extending beyond superficial skin 3
• Topical therapy may be used as adjunct after drainage but should not replace systemic antibiotics when cellulitis is present 2

Follow-Up Strategy

• Reevaluate in 24-48 hours to verify clinical response, especially if using trimethoprim-sulfamethoxazole or tetracyclines for suspected MRSA 1
• Lack of improvement suggests either resistant organisms or inadequate drainage of an abscess 1
• Culture material should be obtained if the patient fails to respond to initial empirical therapy 1