Makindo Medical Notes

Related Subjects: | Anatomy of Skin | Anatomy of the Hand | Anatomy of the Thorax | Anatomy of Muscle Groups | Anatomy of Arteries | Anatomy of Spinal Column | Skin Pathology and Lesions | Skin, Soft Tissue & Bone Infections

Introduction

Skin and soft tissue infections (SSTIs) range from mild superficial cellulitis to life-threatening necrotizing fasciitis. Prompt recognition and correct management are essential to avoid morbidity and mortality. This guide reviews common SSTIs, their pathogens, and antibiotic choices based on current guidelines.

General Principles

• Empirical Antibiotic Therapy: Start based on likely organisms and local resistance data.
• Severity Assessment: Consider systemic toxicity, comorbidities, and site of infection.
• Microbiology Samples: Always take cultures before antibiotics where possible.
• Allergy Considerations: Use alternatives in penicillin allergy (consult microbiology if unsure).
• Multidisciplinary Care: Surgeons, microbiologists, ID specialists, diabetic foot teams as needed.

Cellulitis

• Pathogens: Group A streptococci, Staphylococcus aureus.
• First-line: Benzylpenicillin 1.2 g IV q6h + flucloxacillin 1 g IV q6h.
• Oral step-down: Amoxicillin 500 mg PO q8h + flucloxacillin 500 mg PO q6h.
• Duration: ~7 days, longer if slow response.
• Penicillin allergy: Teicoplanin IV once daily (after loading regimen).

💡 Exam pearl: True cellulitis is usually unilateral — bilateral swelling is more likely venous/lymphatic.

Diabetic Foot Infections

• Pathogens: Polymicrobial (Staph, strep, Gram negatives, anaerobes).
• Mild: Co-amoxiclav 625 mg PO q8h (clindamycin PO if allergic).
• Moderate–Severe: As per cellulitis IV regimens; escalate to co-amoxiclav IV in limb-threatening cases.
• Always involve: Diabetic foot MDT.

Leg Ulcers & Pressure Sores

• Often colonised — treat only if clinical infection (pain, erythema, swelling, systemic signs).
• Pathogens may include Gram-negatives and Pseudomonas, but antibiotics only if infected.
• Wound care and pressure relief are vital — involve tissue viability nurses.

Postoperative Surgical Wound Infections

• Pathogen: Staphylococcus aureus.
• Clean wounds: Flucloxacillin PO/IV.
• Groin/contaminated sites: Co-amoxiclav PO/IV.
• Severe: Discuss with microbiology for tailored cover.

Necrotizing Fasciitis

⚠️ Red flag: Severe pain out of proportion to signs is the hallmark. This is a surgical emergency.

• Pathogens: Group A strep ± anaerobes and Gram negatives.
• Management: Immediate surgical debridement + IV benzylpenicillin + clindamycin + gentamicin.
• Allergy: Clindamycin + gentamicin.

Fournier’s Gangrene

⚠️ Red flag: Necrotizing infection of perineum/scrotum — rapidly fatal without urgent surgery.

• Pathogens: Polymicrobial: strep, coliforms, anaerobes.
• Treatment: Emergency debridement + piperacillin-tazobactam IV. Allergy: clindamycin + gentamicin.

Gas Gangrene

⚠️ Red flag: Clostridial myonecrosis causes rapid shock and death. Treat surgically and medically.

• Pathogen: Clostridium perfringens.
• Therapy: Surgical debridement + IV benzylpenicillin + metronidazole (or clindamycin if allergic).
• Hyperbaric O₂ may be an adjunct in specialist centres.

Animal & Human Bites

• First-line: Co-amoxiclav PO/IV.
• Allergy: Doxycycline + metronidazole.
• Duration: 5–7 days.
• Check: Tetanus & rabies risk (rabies if bite overseas); HIV/hepatitis if human bite.

Bone and Joint Infections

Osteomyelitis and septic arthritis are serious infections needing urgent recognition and treatment. Both require orthopaedic and microbiology input.

Osteomyelitis

• Common cause: Staph aureus.
• First-line: Flucloxacillin IV q6h ± sodium fusidate (if sensitive; monitor LFTs).
• Allergy/MRSA: Clindamycin IV or vancomycin (micro advice).
• Duration: 4–6 weeks (initial IV then oral switch).
• Chronic cases: Often need surgery + prolonged antibiotics.

Septic Arthritis

• Pathogens: Staph aureus, streptococci, Gram negatives, Neisseria gonorrhoeae (young adults).
• First-line: Flucloxacillin IV q6h ± gentamicin if coliform risk.
• Gonococcal: Ceftriaxone 2 g IV OD for 10–14 days.
• Essential: Joint aspiration/washout — this is an orthopaedic emergency.

💡 Exam pearl: Septic arthritis = antibiotics + drainage. Do not delay washout for antibiotics unless patient is septic.

Summary IV Antibiotic Doses (Adults)

References

• CREST Guidelines: Cellulitis in Adults (2005).
• NICE Clinical Knowledge Summaries.
• IDSA Practice Guidelines for SSTI.
• BSAC Bone & Joint Infection Guidelines.

Disclaimer

This material is for educational use and does not replace clinical judgment. Always check local antimicrobial guidelines and involve microbiology/orthopaedics in severe or complex infections.