1. Skin and Soft Tissue Infection
Ellie Sukerman, MD
6/22/17

2. Disclaimer
Will focus largely on bacterial infection here but remember that SSTI can be due to a broad array of organisms especially in immunocompromised hosts (think fungal, mycobacterial, viral)
Also many mimics of SSTI including venous stasis dermatitis, inflammatory skin disorders
Think about vasculitis, pyoderma gangrenosum, Sweet syndrome, GVHD, drug eruptions etc…

3. SSTI Basics Ways to think about defining SSTI:
Purulent vs. non-purulent infection, severity, anatomy
Purulent
(Furuncle, Carbuncle, Abscess, Cellulitis)
Non-purulent
(Erysipelas, Cellulitis, Necrotizing Infection)
Mild = No systemic signs of infection
Mild = cellulitis/erysipelas w/o systemic signs of infection
Moderate = systemic signs of infection
Moderate = cellulitis/erysipelas with systemic signs of infection
Severe:
Failed I&D plus PO abx OR
SIRS criteria OR
Immuncompromised
Failed PO abx OR
SIRS OR
Immunocompromised OR
Signs of deeper infection
Bullae
Skin sloughing
Hypotension
Organ dysfunction

4. SSTI Anatomy Impetigo: Erysipelas: Cellulitis: Abscess:
Involves epidermis only
Erysipelas:
Involves upper dermis and superficial lymphatics
Cellulitis:
Involves deeper dermis and subcutaneous fat
Abscess:
Collection of pus within dermis or subcutaneous space
Necrotizing SSTI:
Includes necrotizing cellulitis, fasciitis and myositis

5. Erysipelas vs. Cellulitis
Less of a clear demarcation on exam
Beta-hemolytic Strep (typically group A) or S. aureus most common
Rarely due to other organisms
Erysipelas
Distinct type of superficial cellulitis; differentiation from cellulitis may not be clear cut
Classically, acute onset with clear demarcation between involved and uninvolved tissue
Beta-hemolytic Strep
Treatment:
Mild cases: pcn PO or IM
Extensive disease: IV pcn G

6. Cellulitis/Erysipelas
BCx or skin aspirate/bx/swab cxs NOT routinely recommended
Perform if: immunocompromised, animal bite, immersion injury
Recommended duration of abx therapy is 5 days
Severe infection, slow response or immunosuppression
May require up to 14d
Transition from IV to PO once signs of clinical improvement and no signs of systemic toxicity
Slow response to therapy should make you consider:
Resistant organisms
Poor adherence to tx
Inadequate source control

7. Abscess Manage if I&D if drainable +/- abx depending on severity
May result from deep infection of hair follicle
Furuncle or “boil” = single infected follicle
Carbuncle = coalesced furuncles
Think S. aureus!
Can also be polymicrobial, fungal, mycobacterial
Manage if I&D if drainable +/- abx depending on severity

8. Necrotizing Fasciitis
Risk factors: DM, drug use, obesity, immunosuppression, surgery, trauma
Clues to differentiate nec. fasc. from cellulitis
Pain out of proportion to exam
Skin color changes red/purple -> blue/gray
Hemorrhagic bullae
Crepitus
Development of anesthesia 2/2 destruction of superficial subcutaneous nerves
Signs of systemic toxicity

9. Necrotizing Fasciitis
Type I
Polymicrobial (mixed aerobic/anaerobic)
Type II
Monomicrobial
Typically group A Strep or other Beta-hemolytic streptococci either alone or in combination with other pathogens, most commonly S. aureus
Other organisms also possible…

10. Necrotizing Fasciitis
Diagnosis = SURGICAL EXPLORATION
Labs, imaging are secondary and should not delay surgical intervention if nec. fasc. suspected
Intraoperative cxs and BCxs
Treatment = Surgical debridement
Empiric abx: broad-spectrum pending cxs
Continue abx until no further debridements needed and pt hemodynamically stable

11. Antimicrobial Management of SSTI
Purulent
(Think S. aureus)
Severe
Moderate
Mild
I&D with cx
I&D
Empiric Rx Options:
Vancomycin
Daptomycin
Linezolid
Ceftaroline
Televancin
TMP/SMX
Doxycycline
n/a
Defined Rx Options:
MRSA: see Empiric
MSSA: nafcillin, cefazolin, clindamycin
MRSA: TMP/SMX
MSSA: dicloxacillin, cephalexin
Ceftaroline: IV cephalosporin with anti-MRSA activity; approved for SSTI and CAP
Televancin: glycopeptide antibiotic; approved for complicated SSTI and nosocomial pna
Would add dalbavancin here too: glycopeptide antibiotic which can be given as single-dose or two-dose regimen Q week x 2 weeks

12. Antimicrobial Management of SSTI
Non-purulent
Severe
Moderate
Mild
Emergent surgical exploration/debridement
(rule out necrotizing process)
Intravenous Rx Options:
Penicillin
Ceftriaxone
Cefazolin
Clindamycin
Oral Rx Options:
Penicillin VK
Cephalosporin
Dicloxacillin
Empiric Rx Options:
Anti-MRSA (vancomycin, daptomycin or linezolid) PLUS
Carbapenem or beta-lactam-beta-lactamase inhibitor PLUS
Clindamycin for anti-toxin effects
Select Defined Rx (necrotizing infections)
Strep pyogenes: pcn + clinda
Clostridial: pcn + clinda
Polymicrobial: vanc + zosyn

13. Adjunctive Management of SSTI
Other measures:
Elevation of affected area
Treatment of predisposing factors
Edema
Venous insufficiency
Cutaneous disorders (e.g., eczema, tinea pedis)
Obesity

14. SSTI Prevention Recurrent cellulitis Recurrent abscesses
Identify and treat predisposing conditions
Consider prophylactic abx (e.g., PO pcn) if >3-4 episodes per year despite attempts to treat or control predisposing factors
Recurrent abscesses
Search for local causes (foreign material, pilonidal cyst etc…)
Consider 5 day decolonization regimen (sparse data on efficacy)
Intranasal mupirocen BID
Daily chlorhexidine washes
Daily decontamination of personal items (towels, clothes etc)

15. Bite Wound Micro Human bite: oral and skin flora, Eikenella
Animal bites:
Host skin flora
Animal oral flora
Pasteurella (characteristically, a rapidly developing infection)
Bartonella henselae (cats)
Capnocytophaga (dogs) -> can cause bacteremia, fatal sepsis

16. Bite Wound Work-up
BCxs indicated in pt with infected bite wound AND signs of systemic infection
If bite wound infected on exam, send gram stain, aerobic & anaerobic cx
Send cxs before initiating abx and note hx of bite wound when ordering
Wound cx NOT indicated in clinically uninfected bite wounds
Eikenella and Pasteurella are fastidious organisms and frequently misidentified

17. Bite Wound Prophylaxis
*also need to consider rabies, Hep B, HIV but won’t cover here
Abx prophylaxis warranted for:
Immunocompromised host (incl DM, asplenic, cirrhosis)
Pre-existing or resultant edema of affected area
Moderate to severe injuries, esp to hand or face
Injuries that may have penetrated the periosteum or joint capsule

18. Bite Wound Abx Prophylaxis/Tx
Administer 1st dose ASAP after injury then complete total of 3-5 days
Several empiric options including:
Amoxicillin-clavulanate (agent of choice)
Doxy/bactrim/pen VK/cipro/moxi/cefuroxime + clindamycin/metronidazole
Lots of options for tx of infection including amox-clav; include aerobic and anaerobic coverage
Poor activity against Eikenella: cephalexin, diclox, erythromycin
Poor activity against Pasteurella: cephalexin, diclox, erythromycin

19. Bite Wound Tetanus Prophylaxis
Previous Doses of Tetanus Toxoid
Clean and Minor Wound
All Other Wounds
Tetanus toxoid-containing vaccine
Human tetanus immune globulin
<3 doses or unknown
Yes No
≥3 doses
Only if last given ≥10 years ago
Only if last dose given ≥5 years ago
For adults, Tdap is preferred in those who have not previously received Tdap.
Td preferred for those who previously received Tdap and when Tdap not available.

20. Fun/Weird Stuff!!
Mesotherapy (injection of medications, plant matter, vitamins etc..for cosmetic purposes) – LOTS of organisms
Aeromonas – traumatic aquatic injury, medicinal leeches
Vibrio vulnificus – saltwater, shellfish/fish wounds
Mycobacterium marinum – fishtanks
Erysipelothrix – fisherman/seafood packers
Mycobacterium fortuitum – nail salon outbreak
Anthrax (cutaneous) – drum making with animal hides
B virus – monkey bite

21. Question 1 Antibiotic therapy for cellulitis:
is always initially IV along with elevation of affected area.
is patient specific and may be IV or PO.
should wait to be chosen based on BCx or skin cx results.
should be continued for 14 days.
should be continued for 5 days.

22. Question 2 Classic signs of necrotizing fasciitis are: Crepitus
Extensive skin involvement with mild pain
Mild cellulitis with severe pain
Bullae
Fever

23. Question 3
You should suspect a hot, erythematous leg is not cellulitis/erysipelas if:
BCxs are negative
this is recurrent cellulitis
the erythema surrounds a venous stasis ulcer
both legs are involved
it is associated with shock

24. Question 4
Preemptive antimicrobial therapy following an animal bite wound should be:
given to all patients
given to immunocompromised patients
PO cephalexin x 3-5 days
administered for 7 days
administered IV

25. Question 5
The most important component in diagnosis of necrotizing fasciitis is:
Imaging findings consistent with the dx
Exploration of tissues in OR
Positive gram stain/cx from tissue demonstrating presence of bacteria
Labs demonstrating leukocytosis and elevated CK
Physical exam findings

26. Resources
IDSA Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014.
Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 2010.
UpToDate.com