What is the appropriate evaluation and treatment for a 25‑year‑old healthy male who developed cellulitis with fever three days after a 1 cm abrasive wound on the dorsum of his right foot?

Management of Cellulitis Following Foot Abrasion in a Young Adult

This patient requires immediate evaluation for deep tissue infection, urgent wound probing to assess for bone or tendon involvement, blood cultures, and empiric antibiotic therapy covering streptococci and staphylococci, with hospital admission if systemic toxicity is present.

Immediate Assessment Priorities

Clinical Evaluation

• Probe the wound with a sterile, blunt metal probe to determine depth and detect communication with deeper structures—a "stony feel" indicates bone contact and requires urgent specialized care 1, 2.
• Measure wound dimensions and assess for surrounding cellulitis extent (erythema, warmth, induration, tenderness) 3.
• Examine for signs suggesting necrotizing infection: skin necrosis, bullae, ecchymoses, crepitus, severe pain disproportionate to findings, or rapid progression despite antibiotics—these mandate immediate surgical consultation 4.
• Check for systemic toxicity: fever, tachycardia, hypotension, or altered mental status, which indicate severe infection requiring hospitalization 4.

Diagnostic Testing

• Obtain blood cultures before starting antibiotics if the patient has fever or systemic symptoms 4, 3.
• Plain radiographs should be obtained to detect foreign bodies (shoe/sock material) and assess for early osteomyelitis 2.
• If bone is palpable on probing or the wound is deep (>3mm), strongly suspect osteomyelitis and consider MRI for definitive evaluation 4, 2.

Risk Stratification and Disposition

Indications for Hospital Admission

• Fever with systemic toxicity (hypotension, tachycardia, confusion) 4.
• Rapidly progressive cellulitis despite initial antibiotic therapy 4.
• Exposed tendon or bone on examination—these require immediate hospital referral for specialized surgical care regardless of infection signs 1.
• Signs suggesting necrotizing fasciitis (skin necrosis, bullae, crepitus, severe pain) 4.

Outpatient Management Criteria

• Mild to moderate cellulitis without systemic toxicity 4.
• No evidence of deep tissue involvement on probing 2.
• Reliable patient who can follow up within 24-48 hours 4.

Antibiotic Selection

Empiric Therapy for Typical Cellulitis

For outpatient management, oral antibiotics targeting β-hemolytic streptococci (the most common pathogen) and methicillin-sensitive Staphylococcus aureus are appropriate 4, 5, 6:

• First-line options: Cephalexin, dicloxacillin, amoxicillin-clavulanate, or clindamycin 4.
• Penicillin or amoxicillin alone are acceptable if streptococcal infection is most likely 4.
• Duration: 5 days is sufficient if clinical improvement occurs; extend to 10-14 days if response is slower 4.

When to Cover MRSA

MRSA coverage is NOT routinely needed for typical cellulitis, even in areas with high community-acquired MRSA rates 4, 5. However, consider MRSA coverage if 4:

• Penetrating trauma (the abrasion may qualify if deep).
• Purulent drainage present.
• Failed initial β-lactam therapy.
• Known MRSA colonization or prior infection.

MRSA coverage options (if needed):

• Oral: Doxycycline, clindamycin, or trimethoprim-sulfamethoxazole (TMP-SMX) 4.
• If using TMP-SMX or doxycycline, add a β-lactam (cephalexin or amoxicillin) for streptococcal coverage, as these agents have uncertain activity against streptococci 4.
• Intravenous (for hospitalized patients): Vancomycin, daptomycin, or linezolid 4.

For Severe Infection Requiring Hospitalization

• Start broad-spectrum parenteral antibiotics covering gram-positive cocci, gram-negative rods, and anaerobes until culture results available 4.
• Options include: ampicillin-sulbactam, piperacillin-tazobactam, or ticarcillin-clavulanate 4.
• Add vancomycin if MRSA risk factors present 4.

Wound Management

Cleansing and Debridement

• Cleanse with sterile normal saline—no need for iodine or antibiotic solutions 2.
• Debride necrotic tissue and surrounding callus to reduce bacterial load and permit deep examination 3, 2.
• Warn the patient that bleeding is expected and the wound will appear larger after debridement 2.
• Do not close infected wounds—this can lead to abscess formation and deeper infection 2.

Adjunctive Measures

• Elevate the affected leg to promote drainage of edema and inflammatory mediators 4.
• Limit weight-bearing and consider crutches to off-load the wound 3.
• Treat predisposing conditions: examine for tinea pedis or toe web maceration, which serve as portals for streptococcal entry 4.

Tetanus Prophylaxis

• Ensure tetanus immunization is current; if outdated or unknown, administer 0.5 mL tetanus toxoid intramuscularly 2.

Follow-Up and Monitoring

Expected Clinical Response

• Clinical improvement should occur within 24-48 hours of starting appropriate antibiotics 4.
• Worsening inflammation in the first 24 hours may occur due to bacterial lysis releasing inflammatory mediators—this does not necessarily indicate treatment failure 4.

Reassessment Triggers

• No improvement after 48-72 hours of appropriate antibiotics suggests:
  • Resistant organisms (consider MRSA or gram-negative pathogens) 4.
  • Deeper infection (abscess, necrotizing fasciitis, osteomyelitis) 4.
  • Incorrect diagnosis (mimicker such as venous stasis dermatitis, contact dermatitis) 5, 7.

If Osteomyelitis Confirmed

• 6 weeks of antibiotic therapy if bone is not resected 2.
• ≤1 week of antibiotics if all infected bone is surgically removed 2.

Critical Pitfalls to Avoid

• Do not assume absence of infection signs means the wound is superficial—exposed tendon or bone always requires specialized care 1.
• Do not routinely cover MRSA in typical cellulitis without risk factors—this leads to unnecessary broad-spectrum antibiotic use 4, 5.
• Do not rely on wound surface cultures—they reflect colonizers, not deep pathogens; blood cultures or deep tissue specimens are more reliable 4.
• Do not delay surgical consultation if necrotizing infection is suspected—mortality increases dramatically with delayed debridement 4.
• Do not close contaminated or infected wounds—this traps bacteria and promotes abscess formation 2.