What antibiotics are recommended for the empirical treatment of necrotizing fasciitis in adults?

Empirical antibiotic treatment for necrotizing fasciitis in adults should cover a broad spectrum of pathogens including Gram-positive cocci, Gram-negative rods, and anaerobes.

Recommended empirical intravenous antibiotics include a combination of:

• Flucloxacillin 1 to 2 g four times a day IV to cover Gram-positive organisms including Staphylococcus aureus.
• Gentamicin initially 5 to 7 mg/kg once a day IV, adjusted by serum levels, to cover Gram-negative bacteria.
• Metronidazole 500 mg three times a day IV to cover anaerobic bacteria.

Alternatively, co-amoxiclav 1.2 g three times a day IV can be used with gentamicin and metronidazole if Pseudomonas aeruginosa is not suspected.

If Pseudomonas aeruginosa is suspected or confirmed, piperacillin with tazobactam 4.5 g three times a day IV is recommended.

For suspected or confirmed MRSA infection, add vancomycin 15 to 20 mg/kg two or three times a day IV or teicoplanin initially 6 mg/kg every 12 hours for three doses, then once daily IV.

Clindamycin (600 mg to 2.7 g daily IV) may be added for its antitoxin effects in severe infections.

Review antibiotic choice based on microbiological results and clinical response, with a minimum course of 7 days and adjustment as needed.

Oral antibiotics may be considered once the patient is stable and able to take oral medication.

This regimen aligns with UK guidelines for severe soft tissue infections and diabetic foot infections, which share similar microbiological profiles and treatment principles.