Skin and soft tissue infections

PEBC

uncomplicated infections

• folliculitis

• impetigo

• carbuncles

• furuncles

• cellulitis

• small skin abscess

complicated infections

• large abscesses

• ulcers

• necrotizing fasciitis

• bites

• burns

involve deep skin structures (fascia, muscle layer)

• need surgical intervention

• can include foot infection in diabetics

• coexisting disease = diabetes, immunocompromised, obesity

cellulitis (definition)

• acute bacterial infection involving the dermis & subcutaneous tissue

• presentation

  • diffuse, poorly defined areas of erythema + warmth, swelling & tenderness

• can be purulent or non-purulent

erysipelas (definition)

• acute infection affecting the upper epidermis & superficial lymphatic vessels

• mostly on face or lower limbs

folliculitis (definition)

• inflammation or infection involving superficial or deep hair follicles, resulting in formation of papules or pustules

impetigo (definition)

• superficial bacterial skin infection that occurs in 2 clincal forms:

  • Non-bollus = presents w/ papules, vesicles & pustules that rupture & develop honey-coloured crusts

  • Bullous = presence of fluid-filled blisters (bullae or vesicles)

common pathogens (SSTI)

• staphylococcus aureus (gram positive)

• B-hemolytic streptococci (groups A,B,C,G) (gram positive)

goals of therapy (SSTI)

1. cure the infection

2. minimize smx

3. prevent recurrence & progression of infection

4. prevent recurrence of skin infection by modifying contributing factors

5. prevent/ minimize s/e associated with medications

risk factors

• CA-MRSA (S. aureus):

  • Health care exposures (prior 12 months)

    • recently hospitalization or surgery

    • residence in long term care facility

    • hemodialysis

  • Patient specific factors

    • known MRSA colonization or past infection w/ MRSA

    • HIV

    • injection drug use

    • homeless

    • MSM (men who have sex with men)

  • Environmental exposures

    • incarceration or working as prison guard, military service

    • living in crowded conditions

    • attending or working in childcare centers

    • playing contact sports or sharing sporting equipment

**MRSA = purulent (pus)

• factors contributing in SSTI include:

  • vascular insufficiency (diabetes, peripheral vascular disease)

  • indwelling devices (catheters)

  • immunocompromised patients (transplants, Cancer, AIDS, critically ill, elderly)

  • socioeconomic status

  • Epidermal skin break (edema, trauma, surgery)

  • Obesity

  • Prior skin & soft tissue infection

assessment of severity (of infection)

uncomplicated SSTI

non-purulent infections:

• Erysipelas = epidermal cellulitis; classic signs = fire engine red and very clear line of demarkation

• Cellulitis = deeper infection

Purulent infections:

• cellulitis (w abscess)

• impetigo

• folliculitis

• furuncles

• carbuncles

• small skin abscess

severity of non-purulent infections

• Mild infection

  • Cellulitis/ erisipelas w/ no focus on purulence /systemic signs or smx

• Moderate infection

  • typical cellulitis/erysipelas w/ SYSTEMIC signs of infection temp (>38), tachycardia (HR >90), tachypnea (RR>24), abnormal white cell count (>12,000 or <400)

• Severe infection

  • pts who FAILED oral antibiotic treatment or those w/ systemic signs of infection, are immunocompromised or have clinical signs of deeper infections like bullae, skin sloughing, hypotension or evidence of organ dysfunction

uncomplicated SSTI non purulent infections

• Erysipelas = infection of epidermal layer = all group A strep

• Cellulitis = infection of dermis, subdermal tissue = mostly Group A strep

• pathogens:

  • normal host = strep sp. (Groups A,B,C,G) > > > S. aureus (including CA-MRSA)

  • immunocompromised, diabetics = Polymicrobial

  • post-operative wound infections = streptococcus pyogenes

• clinical sx:

  • hallmark signs = Erythema, warmth, swelling, tenderness

  • Lymphadenopathy

  • can have abscess formation

• diagnosis

  • when pts lack hallmark clinical features of infection or have bilateral or atypical findings: rule out other dx (gout, DVT, Venous stasis dermatitis)

risk factors (cellulitis)

• tinea pedis

• diabetes

• peripheral vascular disease

• peripheral edema

• obesity

• history of cellulitis

treatment non purulent cellulitis (erysipelas)

• non pharm = evaluation for skin abscess, drainage if present

• pharmacological = 5 days, longer in severe/ complicated)

  • mild = penicillin VK, cephalexin, cefadroxil, clindamycin

    • *clinda - reserved for pts who cant take B-lactams (anaphylactic allergy)

  • moderate = IV Penicillin, Cefazolin, Ceftriaxone, Clindamycin

  • severe = [Piperacillin/ tazobactam or Imipenem/Meropenem ] + vancomycin (MRSA)

• treat empirically for CA-MRSA if

  • non-response to anti-MSSA, anti-streptococcal coverage

  • concern for severe/ necrotizing infection

  • CA-MRSA risk factors (military, failed oral abx therapy etc)

severity of purulent infections

• MILD infection:

  • impetigo, furuncle, carbuncle, abcess — no systemic signs or smx

• MODERATE infection:

  • systemic signs of infection: temp (>38), tachycardia (HR >90), tachypnea (RR>24), abnormal white cell count (>12,000 or <400)

• SEVERE infection:

  • failed incision + drainage & oral antibiotics or those w/ severe systemic signs of infection or immunocompromised pts

impetigo

• purulent infection

• superficial, nonfollicular pustules

• usually on the face and extremities

• common pathogens = Staphylococcus aureus, B-hemolytic streptococcus sp, MSSA

• risk factors:

  • children (peak = 2-5)

  • equal in male and female

  • tropical regions, warmer months

  • poor hygiene

  • minor skin trauma (insect bites)

  • may be highly contagious, patients often colonized prior to infection

• clinical presentation:

  • honey crusted lesions

  • pustules that rupture —> then form thick crust

impetigo treatment

• Mild = topical:

  • Mupirocin ointment x 5 days (preferred)

  • Fusidic acid x 5 days

• Moderate/ Severe = Oral:

  • (Penicillin? ) Cephalexin, Cloxacilin x 7 days

  • clindamycin x 7 days if severe penicillin allergy

  • multiple sites of lesions or failed therapy

• consider CA-MRSA if rapidly progressing

  • TMP/SMX

  • Doxycycline

  • Clindamycin

folliculitis

• superficial purulent skin infection localized at hair follicles

• pathogens: Polymicrobial

  • Strep

  • Staph (always think this if exposure to water)

  • Candida spp

  • occasionally: Pseudomonas aeruginosa

• risk factors:

  • Nasal carriage of S. aureus

  • Pools, Hot tubs (pseudomonas)

• clinical sx:

  • multiple clustered lesions <5mm

  • erythematous

  • pruritic

  • pus

• treatment:

  • lesions may spontaneously drain and resolve

  • topical treatment:

    • warm compress & antimicrobial cleanser (e.g. benzoyl peroxide)

    • topical abx =

      • Mupirocin ointment x 5-7 days

      • Clindamycin gel/solution x 7-10 days OR fusidic acid ( ⬆ resistance of S.aureus)

  • oral or parenteral antimicrobials if systemic infection (rare) x 7-10 days

    • persistent s&s after 2-3 weeks of therapy

    • MRSA not suspected = Cephalexin

    • MRSA suspected =

      • Doxycycline

      • TMP/SMX

      • Clindamycin

furuncles/ carbuncles (and skin abscesses)

• purulent infections

• furuncle = infection of hair follicle (boil)

  • small skin abscess extending through dermis into subcut tissue

  • painful, tender and pus-filled —> drains spontaneously

• carbuncle = coalescence of several inflamed hair follicles/ boils

  • may present w fever (mostly in diabetics)

• pathogens = S. aureus

treatment:

• mild = incision & drainage of abscess, warm water or saline compresses for 20-30 mins QID

  • may consider antimicrobials for small abscesses to ⬇ recurrence

• antimicrobials for moderate to severe

• moderate = incision & drainage

  • Empiric =

    • SMX/TMP or

    • Doxycycline

  • defined MRSA = SMX/TMP

  • Defined MSSA = Cephalexin

• Severe = incision & drainage

  • Empiric or defined MRSA =

    • Vancomycin

    • Linezolid

    • Daptomycin

  • MSSA =

    • Cefazolin

    • Clindamycin (documented b-lactam allergy)

necrotizing SSTIs

• polymicrobial

• monomicrobial = Group A strep (flesh eating bacteria). s. aureus, CA-MRSA, Clostridium perfringens

• risk factors:

  • IVDU

  • Immunosuppression

  • DM

  • Obesity

  • Elderly

  • Alcohol

  • Peripheral vascular disease

  • AIDS

  • Cancer

• Treatment:

  • aggressive debridement, supportive care and IV antibiotic therapy

• Empiric therapy:

  • Broad spectrum = Carbapenems, Pip/Tazo

  • MRSA = Vancomycin, Daptomycin, Linezolid

  • Inhibit toxin production = Clindamycin (added onto above therapy)

animal bites

• pathogens

  • S. aureus (gram positive)

  • strep (gram positive)

  • mouth anaerobic pathogens (Pasteurella spp, Elkenella spp)

• treatment (5-14 days):

  • 5-14 days = Amox/clav (po)

    • goal = target aerobes AND anaerobes

    • if allergy = Moxifloxacin + Clindamycin ?? (old notes)

    • alternatives =

      • Cefuroxime,

      • Doxycycline,

      • SMX/TMP,

      • Levofloxacin, Moxifloxacin or Carbapenems (With Metronidazole or Clindamycin as needed for anaerobic coverage)

  • tetanus toxoid, rabies post-exposure prophylaxis (PEP)

human bites

• deep wounds

• pathogens:

  • S. aureus

  • S. epidermitis

  • Streptocci

  • Mouth Anaerobes (Peptostreptococci)

  • S. viridans

  • Eikenella spp

• empiric treatment

  • 5 - 14 days

  • up to 14 days = if later presentation/ more complicated wound

  • Amox/clav po will target most pathogens

  • alternatives =

    • FQ

    • Doxy or

    • Carbapenems

    • w/ Metronidazole as needed for anaerobic coverage

    • or moxifloxacin monotherapy

• tetanus toxoid

monitoring SSTI

trauma wound (/ compound fractures)

• classified as contaminated &/or dirty wounds

• antimicrobials = therapeutic not prophylactic

• Empiric abx:

  • depend on trauma location & extent

  • visceral & mucosal sites = need broad-spectrum agents (cover for pseudomonas if water related wound, metronidaole for soil contaminated wound)

    • ciprofloxacin + metronidazole

    • carbapenem

    • cefazolin + AMG

    • pip-tazo

• the bigger the skin break the broad the therapy

carbapenems

• Meropenem, Imipenem

• associated w/ ⬇ seziure threshold

  • Risk of seizures increased in the presence of poor renal function; caution is advised.

• s/e = C.diff, Hypersensitivity reactions (ranging from minor rashes to anaphylactic shock). Nausea, vomiting, diarrhea.

• useful for difficult to treat organisms w/ multi-resistance (SPACE/SPICE, ESBLs)

• good for mixed infections (gram positive/negative, Pseudomonas)

• do not use ertapenem for pseudomonas spp or Acinetobacter

• DDI = Probenecid ⬆ serum levels.

  • Meropenem may decrease valproic acid levels.

ceftriaxone

• very good coverage against S.penumo

• Bactericidal, time-dependent killing

• 3rd gen with +++ gram negative coverage (E.coli, klebsiella, serratia, proteus, morganella)

• all cephalosporins lack coverage against listeria, atypicals and enterococci

• s/e = rash, nausea, diarrhea

• rare s/e = Neurotoxicity/ seizure (older age, renal dysfunction, IV admin, underlying CNS disorder)

vancomycin

• inhibits cell wall formation; time-dependent killing

• s/e = vancomycin infusion reaction: flushing, hypotension (with fast infusion), vancomycin-induced thrombocytopenia

• May cause ototoxicity, nephrotoxicity if receiving other drugs with these effects.

• target trough = 10-20 mg/dL (for severe deep seated infections: 15-20)

• target AUC = 400-600

SMX/TMP

• s/e = Rash, pruritus. May cause hyperkalemia; risk is increased in elderly and renal impaired patients. Hypersensitivity reactions, nausea, vomiting, diarrhea, rash, false↑in serum creatinine, renal impairment, neutropenia, thrombocytopenia, anemia, agranulocytosis, hypoglycemia (in malnourished pt or pts with renal or hepatic impairment), photosensitivity

• CI = severe liver disease

• caution: G6PD deficiency

• covers gram positive & negative

• Hyperkalemia with ACE inhibitors and ARBs

• Administer with at least 8 ounces of water

• DDI: 2C9 inhibitor, 3A4 substrate: ⬆levels of carvedilol, digoxin, phenytoin, INR

  • levels ⬇w/ 3A4 inducers (carbamazepine, phenobarb, phenytoin, rifampin)

Fluroquinolones (FQ)

• Ciprofloxacin, Levofloxacin, Moxifloxacin

• resp: Levo & moxi

• Bactericidal

• S/e: GI (N/V/D), HA, dizziness, ⬆QTc prolongation (highest = moxi), Tendonopathy/ tendon rupture (↑ risk if concomitant CS, ≥60 years & women) ⬆/ ⬇blood glucose, ⬆ C.diff infection, seizures, articular damage in kids. Peripheral neuropathy

• DI: CYP1A2 inhibition —> ⬆ levels of clozapine, duloxetine, MTX, rasagiline, vareniciline

  • increase INR by displacing warfarin

• Caution: ≥60 years, renal impairment (dose adjust), solid organ transplant, <18 y/o

• monitor: joint pain, blood glucose (if DM)