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Peds ID Abx QOTW #10 Answer

b) Obtain wound cultures from I&D or aspiration

e) Send home with Rx for Bactrim or Clindamycin

Q10graphHow others answered

Staphylococcus aureus Abscess

  • The vast majority of patients who present with complaints of a “spider bite” have pyogenic abscess, and by far the most common cause is S. aureus, followed by Group A Streptococcus
  • Community-acquired methicillin-resistant S. aureus (CA-MRSA) was by far the most common organism in the early 2000’s, peaking around 2009
  • Most recent data nation wide has suggested about 40% of S. aureus is now MRSA and the remaining portion is methicillin-sensitive (MSSA)
  • This is consistent with our institutional findings (see Antibiogram)
  • Remember in injection drug users Gram negatives and anaerobes may also be involved in such abscesses

Management of Abscesses 

  • I&D has been a mainstay for large abscess without cellulitis or systemic symptoms
    • Cure rates range from about 70-80% with I&D alone
    • I&D or aspiration will lead to earlier symptomatic improvement
  • Recent data suggests that a course of antibiotics may improve outcomes further(1,2)
    • 1. Talan DA. et al.  N Engl J Med 2016;374:823-32
    • 2. Daum RS. et al. N Engl J Med. 2017 Jun 29;376(26):2545-2555
    • While these studies used 10 days of antibiotics, we routinely use 5-7 days for skin infections, so I would recommend giving a short course of 5-7 days for abscess that requires I&D
    • Further data is needed to determine the appropriate length of therapy post I&D
    • For small abscess (<2cm) with or without cellulitis a short course of 5-7 days of antibiotics is likely to be effective
  • Abscess with systemic symptoms should be given IV antibiotics with I&D until bacteremia is ruled out

Case Discussion

  • Blood cultures & admission are not necessary without systemic symptoms
  • However, this patient is young with a large abscess (would consider this moderate disease); it would be prudent to get a culture to guide future therapy options
  • IV therapy is unnecessary if you have an option that is likely to work against MRSA in this context
  • At our institution, TMP-SMX has >95% activity against MSSA and MRSA
  • Clindamycin overall is effective against all S. aureus but we do not have data to separate outpatient & inpatient isolates
  • Equal effectiveness was seen for Clindamycin and TMP-SMX regardless of the organism, suggesting that TMP-SMX is effective for Group A streptococcus
  • Cephalexin is unnecessary to be added to TMP-SMX based on DMID study(1)
    • 1. Miller LG. et al. N Engl J Med. 2015 Mar19;372(12):1093-103
  • Cephalexin alone does not have adequate coverage for MRSA, which still represents 40% of S. aureus abscess