Natasha Press, MD, FRCPC (biography and disclosures)
What I did before
A 32 year old woman, otherwise healthy, presented with a “spider-bite”. On exam, she had a tender abscess on her buttock. It was associated with some surrounding cellulitis but no fever or other systemic features. I recommended incision and drainage, but she wasn’t keen on it, so I gave her a 7-day prescription for cephalexin (keflex) 500 mg po qid.
What changed my practice
The woman returned to the office 1 week later. The abscess had increased in size and another one had appeared on her labia. She was in significant discomfort and reported no improvement with the cephalexin. Incision and drainage of her abscesses were done, and the culture result from the swab showed community-associated methicillin resistant Staphylococcus aureus (ca-MRSA). This patient did not improve because her abscesses were caused by ca-MRSA which is resistant to cephalexin and other beta-lactam antibiotics. As well, an incision and drainage should have been done when she initially presented.
Abscesses caused by ca-MRSA are often multiple, appearing on the buttock and groin, as well as other parts of the body. Treatment includes incision and drainage, with the addition of antibiotics if the abscess is large or there is surrounding cellulitis, incomplete drainage, or fever  Oral antibiotics effective against ca-MRSA usually include septra, doxycycline, and clindamycin.
If a patient presents with cellulitis associated with an abscess or wound, there is a greater chance that it could be due to ca-MRSA (cellulitis by itself, without any abscess/wound, is usually due to Group A Streptococcus). In these cases, ca-MRSA should be covered empirically, but Group A Streptococcus should be covered as well. Unfortunately, the antibiotics effective against ca-MRSA (septra, doxycycline, clindamycin) are not reliable for treatment of Group A Streptococcus . Many doctors, therefore, will prescribe both cephalexin to cover Group A Streptococcus, as well as septra or doxycycline to cover the ca-MRSA.
What I do now
Now, when I see a patient like the woman in this case, I incise and drain the abscesses and prescribe septra 1 DS tablet po bid and cephalexin 500 mg po qid for 5-14 days.
Key learning points:
- Think of ca-MRSA in any patient presenting with an abscess and associated cellulitis.
- Perform incision and drainage of the abscess at the time of presentation. Outline to patients this is important for improved outcomes.
- Initiate empiric antibiotics which cover Group A Strep (eg. cephalexin) AND ca-MRSA (eg. septra, doxycycline, or clindamycin)
- Counsel patients about strategies to reduce exposure to family members. I recommend that they cover the abscesses/wound, and wash their hands frequently.
- Recurrences of ca-MRSA are common and frustrating. If a recurrence develops, they should have incision and drainage and receive an antibiotic which covers ca-MRSA.
References: (Note: Direct article downloads and article requests require a login ID with the BC College of Physicians website)
 Moellering, RC Jr. Clin Infect Dis 2008:46:1032-7. (Article Request Form)
 Tan K, Romney M, Champagne S. AMMI, 2008