Necrotising Fasciitis

LKL, a 54-year-old male was a referred case from a primary hospital for further management. He has been diagnosed with necrotising fascilitis and is currently on:

-IV metronidazole 500 mg tds

-IV cefepime 1g bd

-Mepilex dressing (every 3 days)

Issues of interest:

-What are the rationale of using IV metronidazole and IV cefepime?

-What is Mepilex dressing?

Findings:

Necrotising fasciitis ('decaying infection of the fascia'), is a soft tissue infection commonly known as flesh-eating disease. It consists of 4 types:

Type 1: Streptococci, Group A, C, G

Type 2: Clostridia sp.

Type 3: Polymicrobic: aerobic+anearobic

Type 4: Community-acquired methicillin-resistant Staphylococcus aureus (MRSA)

These bacteria proliferate in an environment of local tissue hypoxia in patient with trauma, recent surgery or medical compromise (e.g. diabetes mellitus).

All types of necrotising fasciitis require prompt surgical debridement and antibiotics. Gram stain/culture is used to determine the etiology.

If streptococci/clostridia sp. are the identified major pathogens, the drug of choice is penicillin G (alternative: clindamycin).

To ensure adequate treatment, there must be coverage for aerobic and anaerobic bacteria. The anaerobic coverage can be provided by metronidazole or third-generation cephalosporins.

If the etiology is polymicrobial, the drug of choice is imipenem or meropenem. Vancomycin is added if MRSA is suspected.

In LKL, IV metronidazole and IV cefepime have been started. IV metronidazole is for anaerobic coverage while IV cefepime, a 3rd-generation cephalosporin, provides coverage for Streptococci. [Note: It is not known if the previous hospital has carried out Gram stain]

Mepilex is an absorbent, atraumatic dressing made from polyurethane foam which absorbs exudate and maintains a moist wound-healing environment whilst minimising the risk of maceration.

References:

1. Mayner M. Necrotising fasciitis [Online].2009 March 25 [cited 2009 November 15]; Available from: URL: http://emedicine.medscape.com/article/784690-overview

2. The Sanford Guide to Antimicrobial Therapy 2006. 36th ed. p. 41.

3. Wikipedia. Necrotising fasciitis [Online]. 2009 November 10 [cited 2009 November 15]; Available from: URL: http://en.wikipedia.org/wiki/Necrotizing_fasciitis

4. SMTL Dressings Datacard. Available from: URL: http://www.dressings.org/Dressings/mepilex.html