Necrotising Fasciitis: Treatment Rationale

• broad-spectrum antibiotics should be administered that cover the most common aetiologies for necrotising fasciitis. These include
• type 1 infections (mixed infections with anaerobes such as Bacteroides or Peptostreptococcus with a facultative anaerobe such as Enterobacteriaceae [Escherichia coli, Enterobacter, Klebsiella, Proteus], MRSA, or non-group A streptococcus) and
• type II infections (group A streptococcus [i.e., Streptococcus pyogenes ])
• A foul smell in the lesion strongly suggests the presence of anaerobic organisms.
• The maximum doses of the antibiotics should be used, with consideration of the patient's weight and liver and renal status.
• Possible regimens include a combination of penicillin G and an aminoglycoside (if renal function permits), as well as clindamycin (to cover streptococci, staphylococci, gram-negative bacilli, and anaerobes).
• A more specifically targeted antibiotic regimen may be begun after the results of initial gram-stained smear, culture, and sensitivities are available.
• Although some necrotizing infections may still be susceptible to penicillin, clindamycin is the treatment of choice for necrotizing infections

Rationale for Clindamycin

• Unlike penicillin, the efficacy of clindamycin is not affected by the inoculum size or stage of bacterial growth
• Clindamycin is a potent suppressor of bacterial toxin synthesis
• Subinhibitory concentrations of clindamycin facilitate the phagocytosis of GABS
• Clindamycin reduces the synthesis of penicillin-binding protein, which, in addition to being a target for penicillin, is also an enzyme involved in cell wall synthesis and degradation
• Clindamycin has a longer postantibiotic effect than β-lactins such as penicillin
• Clindamycin suppresses lipopolysaccharide-induced mononuclear synthesis of tumor necrosis factor-α (TNF-α)
• Consequently, the success of clindamycin also may be related to its ability to modulate the immune response

Antibiotics

• Broad-spectrum beta-lactam drugs such as imipenem cover aerobes, including Pseudomonas species.
• Ampicillin sulbactam also has broad-spectrum coverage, but it does not cover Pseudomonas species; however, necrotizing fasciitis caused by Pseudomonas aeruginosa is unusual
• If staphylococci or gram-negative rods are involved, vancomycin and other antibiotics to treat gram-negative organisms other than aminoglycosides may be required.
• The use of vancomycin to treat methicillin-resistant Staphylococcus aureus (MRSA) may depend on the clinical situation. For example, use may depend on whether a nasocranial infection is present, or it may need to be avoided in patients who are likely to be carriers of MRSA (eg, those with diabetes, those who use illicit drugs, those undergoing hemodialysis).
• For patients with a penicillin allergy, vancomycin monotherapy may be used

References:

1. www.bmjbestpractices.com
2. http://emedicine.medscape.com/article/2051157-treatment#d10