Wound Cellulitis

Wound cellulitis is spreading soft tissue infection around a surgical, traumatic, burn or bite wound, with erythema and induration beyond the wound edge. It is the commonest form of surgical site infection and is caused by Staphylococcus aureus, streptococci, and in abdominal or perineal wounds, Enterobacterales and anaerobes.

• Risk factors: diabetes, obesity, smoking, malnutrition, contamination, long operation, haematoma, foreign material, immunosuppression, HIV, poor hygiene, delayed presentation.
• Clostridial and group A streptococcal necrotising infection are rare but life threatening.

Pain, warmth, erythema and swelling spreading beyond the wound margin, purulent discharge, wound dehiscence, fever, usually 3 to 7 days after injury or surgery.

• Differential diagnosis: normal postoperative inflammation, haematoma, suture reaction, wound abscess, necrotising fasciitis, deep vein thrombosis, contact dermatitis, retained foreign body, deep organ space infection.
• Complications: wound abscess, dehiscence, necrotising fasciitis, bacteraemia, osteomyelitis, prosthetic infection, incisional hernia, tetanus, delayed healing.

Clinical, with swab culture of purulent wound discharge.

• Full blood count, CRP, glucose, blood cultures if febrile; ultrasound for collections; CT for deep infection.
• Check tetanus status; HIV test where indicated.

Open and drain any pus, give antibiotics for cellulitis, and treat contributors.

• Supportive: remove some or all sutures when pus is present, irrigate, pack and dress, analgesia, elevate, optimise glucose and nutrition, stop smoking, tetanus toxoid 0.5 mL IM if due.
• Pharmacological: cellulitis without abscess: flucloxacillin 500 mg to 1 g four times daily for 5 to 7 days (clindamycin 300 to 450 mg three times daily if penicillin allergic). Abdominal, perineal or groin wounds: amoxicillin clavulanate 625 mg three times daily, or ceftriaxone 2 g IV daily with metronidazole 500 mg IV every 8 hours. MRSA risk: add cotrimoxazole 960 mg twice daily or vancomycin 15 to 20 mg/kg IV every 12 hours. Necrotising infection: piperacillin tazobactam 4.5 g IV every 6 hours with vancomycin and clindamycin 600 to 900 mg IV every 8 hours.
• Procedures: incision and drainage; surgical debridement; negative pressure dressing once clean; removal of infected prosthesis or mesh.
• Special groups: pregnancy and post caesarean, amoxicillin clavulanate or cefalexin; diabetes, insulin and tight control; HIV, treat and screen; children, weight based doses.
• Red flags: pain out of proportion, crepitus, skin necrosis or bullae, rapidly spreading erythema, hypotension, fever beyond 48 hours of antibiotics, deep dehiscence.
• Follow-up: daily wound review until clean; surgical review for non healing; prophylaxis planning for future surgery.