Complicated Skin and Soft Tissue Infection

Key facts

• A complicated skin and soft tissue infection (cSSTI) goes deeper than a surface wound or minor cellulitis, involving subcutaneous tissue, fascia, or muscle.
• It often arises after surgery or trauma, or in people with diabetes or reduced circulation, and can spread rapidly without prompt treatment.
• Systemic antibiotics that reach deep tissue are the cornerstone of treatment; moxifloxacin is one option valued for its activity against both gram-positive bacteria and certain anaerobes.
• Seek urgent care for rapidly spreading redness, severe pain out of proportion to the wound's appearance, dark or blistered skin, or fever with shaking chills.

What makes an infection "complicated"

A cSSTI differs from ordinary cellulitis because the infection has moved past the skin surface into subcutaneous tissue, fascia, or muscle. It commonly develops after surgery or trauma, or in people whose diabetes or poor circulation slows healing and weakens local defences against infection. Because the infection sits in deeper tissue, it can progress quickly and needs prompt, systemic treatment rather than topical care alone.

How cSSTIs are treated

Topical antiseptics alone are not enough once an infection has penetrated beyond the skin surface. Systemic antibiotics that reach deep tissue are the cornerstone of management. Moxifloxacin is one option used for cSSTIs, valued for its broad activity against gram-positive bacteria such as Staphylococcus aureus and certain anaerobes that thrive in poorly oxygenated deep tissue. Wound care, drainage of any abscess, and treatment of underlying conditions, such as bringing blood sugar under control in someone with diabetes, support recovery alongside antibiotic therapy.

When to see a doctor

Seek urgent medical attention for rapidly spreading redness, severe pain out of proportion to the wound's appearance, dark or blistered skin, or fever with shaking chills. These signs may point to necrotising fasciitis, a surgical emergency that needs immediate treatment.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.