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

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…

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

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

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

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

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

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

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…

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

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

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

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

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)

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

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

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

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

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.

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

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.

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

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

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

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

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