The Infectious Diseases Society of America just updated their 2005 guidelines for treatment of skin and soft tissue infections (see DOI: 10.1093/cid/ciu296). The guideline deals with minor infections and up to life threatening ones, but I will focus on ones seen/treated in primary care (there is also an algorithm for wound infections, which I will leave to you to investigate).
–-Mild nonpurulent infections (cellulitis, erysipelas): Where mild infection is defined as skin infection without systemic signs of infection (>38 deg C, tachycardia >90, tachypnea >24,or WBC >12K or <400, or immunocompromized):
–Blood culture/biopsies etc. only if patient is immunocompromized (and these patients should be admitted/get IV antibiotics)
–Should use antibiotic with anti-strep activity for 5 days, then extend if necessary after further evaluation. They do note that many clinicians (which includes me) like to cover methicillin-sensitive staph (MSSA). Also, consider covering methicillin-resistant (MRSA) if severe infection, nasal colonization with MRSA, injection drug use.
–In lower extremity cellulitis, examine interdigital toe spaces to look for fissuring, scaling, maceration which could lead to recurrent cellulitis (I’ve had a couple of patients with recurrent lower extremity cellulitis and bad fungal infections of toenails or interdigitally, who did not have further cellultitis when those were treated. I would also add that patients with venous insufficiency and recurrent cellulitis seem to do better with compression stockings.) Consider prophylactic antibiotics in patients with recurrent infections (3-4 episodes/yr) , e.g. with oral penicillin or erythromycin for 4-52 weeks or benzathine penicillin IM 2.4M units every 2-4 weeks.
–Dog/cat bites — give preemptive therapy for 3-5 days in those with more severe bites or immunocompromized (they note that patients with relatively minor dog bites, not involving the face, hand, or foot found a pretty low incidence of infection — 16% — and may not justify routine antibiotic administration, esp if there is good followup available. Give amox-clavulanate 875/125 bid. for human bites, always give antibiotics). Give Td or Tdap if not given within past 10 years, consider rabies prophylaxis, do not generally close wounds except on face, and give azithro if concerned about cat scratch disease.
–In terms of general treatment, MRSA is unusual cause of cellulitis (study in cellulitis patients at a medical center with high incidence of other MRSA-related skin infections found that cefazolin or oxacillin was successful in 96% of the patients. Another recent study not referenced in this article found greater efficacy of cephalexin to TMP/SMX, and, I would add, some of the agents used to treat MRSA, esp TMP-SMX and doxycycline, are less active against strep).
–Antibiotic recommendations: pen VK (I do not use this since by inspection cannot rule-out staph infection), cephalosporin, dicloxacillin, or clindamycin orally — see doses under impetigo/ecthyma
–Impetigo/ecthyma (ecthyma is deeper infection, lesions usually begin as vesicles which rupture, then get circular erythematous ulcer with adherent crusts, and typically leaves a scar
–Gram stain and culture pus or exudates to see if staph or strep, but treatment without this is reasonable in typical cases
–Bullous or nonbullous impetigo: can use oral therapy or topical, though oral therapy preferred if multiple lesions
–Therapies: topical — use either mupirocin or retapamulin bid for 5 days; oral — 7 days of therapy active against staph (unless culture shows strep alone), with MSSA agent (dicloxacillin 250 qid, cephalexin 250 qid, though I usually use 500 bid with good effect, amox-clav 875/125 bid), or if MRSA suspected can use doxycycline 100 bid , clindamycin 300-400 qid, or TMP/SMX 1-2 DS tabs bid.
–Purulent skin infections/abscesses
–Gram stain and culture are recommended (though not for inflamed epidermoid cysts).
–I&D is recommended for inflamed epidermoid cysts, and abscesses (including carbuncles, large furuncles).
–Use of antibiotics should be based on presence or absence of systemic inflammatory response (T>38C or <36C, tachypnea>24, tachycardia >90, WBC>12000 or <400)
–Antibiotic for MRSA is recommended in those who fail initial antibiotic treatment or have impaired host defenses. Also for those with systemic symptoms as above.
–For those with recurrent abscesses, look for local causes (eg pilonidal cyst, hidradenitis or foreign body), drain and culture, then treat with 5 to 10 days of an active antibiotic. Consider 5-day decolonization regimen (e.g., intranasal mupirocin, daily chlorhexidene washes, daily decontamination of personal items) and evaluate for neutrophil disorders if recurrent abscesses began in childhood. They do mention bleach baths (1/4-1/2 cup of bleach per full bath) — see here for a previous blog that promots bleach baths and I have had a few people email me with very positive stories. Data is not great for the 5-day decolonization regimens they cite. I would also add that I have seen a patient with apparent recurrent abscesses on his hands, which turned out to be a herpetic whitlow.
–Choice of antibiotics for empiric therapy: TMP/SMX 1-2 DS tabs bid or doxycycline/minocycline 100mg bid. For culture-guided therapy: dicloxacillin 500 qid or cephalexin 500 qid (they did not include clindamycin in the empiric therapy. Not sure why. I have certainly had much success with that and it covers strep if needed.)
Geoff