Management of Skin & Soft Tissue Infections of Skin & Soft Tissue Infections David H. Spach, MD Professor of Medicine Division of Infectious Diseases University of Washington, Seattle

SSTI Infections & Animal BitesDavid H. Spach, MD

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Management of Skin & Soft Tissue Infections

David H. Spach, MD

Professor of Medicine

Division of Infectious Diseases

University of Washington, Seattle

Case History: Skin & Soft Tissue

• Which of the following is true regarding impetigo?

1. Penicillin is the optimal oral therapy

2. More than 90% are caused by Group A Streptococcus alone

3. Impetigo usually causes major systemic toxicity

4. If localized, Mupirocin is an effective therapy

Impetigo (Pyoderma)

• Cause- Staphylococcus aureus & Streptococcus pyogenes

• Risk factors - Economically disadvantaged- Young children

• Clinical Manifestations- Typically located on face and extremities- Vesicles → Pustules → Honey-colored crusts

• Treatment- Mupirocin (Bactroban): topical 2% ointment - Penicillinase-resistant Penicillins- First or Second Generation Cephalosporins

From: Bisno AL, Stevens DL. N Engl J Med 1996;334:240-6.

Feingold DS. Semin Dermatol 1993;12:331-5.

Mertz PM et al. Arch Dermatol 1989;125:1069-73.


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• A 34-year-old man presents with fever, chills, and evidence of cellulitis on his right arm. He has a T= 39.0°C, marked redness on his right arm, and a WBC of 16,200. He is started on cefazolin(Kefzol).

• 24 hours later his temperature is 37.6°C and his WBC count is 10,800. He feels much better, BUT the redness on his arm has extended far beyond where it was 24 hours ago. The color of the red is slightly darker.


• What would you recommend doing with the patient’s antimicrobial therapy at this point?

1. Change cefazolin to vancomycin2. Change cefazolin to imipenem3. Change cefazolin to daptomycin4. Make no antimicrobial changes

Cellulitis

• Cause- Common: Staphylococcus aureus & Streptococcus sp.- Less common: H. influenzae, S. pneumoniae, gram- bacilli

• Risk factors - Local trauma, abrasion, or skin lesion- Impaired lymphatic drainage of extremity

• Clinical Manifestations- Typically located on extremities- Local (tenderness, erythema, & warmth), fever, chills, leukocytosis


Sachs MK. Arch Dermatol 1991;127:493-6.


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Treatment of Streptococcus pyogenes

• In the following list of oral antimicrobial agents, pick TWO that SHOULD NOT be chosen to treat Streptococcal pyogenes (group A streptococcus)?

1. Trimethoprim-sulfamethoxazole (Bactrim, Septra)2. Levofloxacin (Levaquin)3. Amoxicillin-clavulanic acid (Augmentin)4. Cephalexin (Keflex)5. Ciprofloxacin (Cipro)6. Linezolid (Zyvox)

Streptococcal Ecthyma


Erysipelas


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Erysipelas

• Cause- Common: Streptococcus pyogenes (Group A)- Less common: Groups G, C, and B streptococci, S. aureus

• Risk factors - Local trauma, abrasions, impaired lymphatic drainage

• Clinical Manifestations- Superficial (raised) cellulitis with sharply demarcated border- Involvement of lower extremities more common than face- Blood cultures positive in only 5%

• Treatment- Penicillinase-resistant Penicillins- First or Second Generation Cephalosporins

From: Chartier C et al. Int J Dermatol 1990;29:459-67.

Bisno AL, Stevens DL. N Engl J Med 1996;334:240-6.


� A 62-year-old man is admitted to the hospital with cellulitis. Which of the following is NOT a complication associated with this infection?

1. Glomerulonephritis2. Rheumatic fever

Hand Cellulitis


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• This rash began about 5 days after a skiing trip in Canada. The rash itches. The patient is afebrile and otherwise doing well. In exam, it appears the hair follicles are involved.

• What do you think is going on?

� A 28-year-old man presents with a 3-day history of sinusitis symptoms and a 12-hour history of right eye swelling. He has a temperature of 38.5°C, eyelid edema, and eyelid erythema. He can not spontaneously open his right eyelid, but his vision and extra-ocular movements are intact. The most likely diagnosis is:

1. Blepharitis2. Varicella-Zoster infection3. Preseptal (periorbital) cellulitis 4. Postseptal (orbital) cellulitis


Case History: Groin Rash 1


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Case History: Groin Rashes


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Erythrasma

• Cause- Corynebacterium minutissimum

• Treatment- Erythromycin: 250 mg PO qid x 5-7d- Clindamycin: 2% topical

• Risk factors- Diabetes- Male- Obesity


� A 33-year-old man cut his hand on a piece of broken glass

while cleaning out an aquarium. Several weeks later he noted

a painful, draining nodule on his hand. He now has several

more nodules proximal to the first nodule. The most likely

diagnosis is:

1. Mycobacterium marinum

2. Sporotrichosis

3. Aeromonas hydrophilia

4. Pseudomonas aeruginosa

Nodular Lymphangitis

• Mycobacterium marinum

• Sporotrichosis

• Cutaneous Nocardia


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• A 22-year-old man from Malawi, Africa presents to the emergency room with left hip pain. On examination, he has a T = 38.8°C, firm, woody edema of the left upper thigh and left buttock, and pain with weight-bearing of his left leg.

• His WBC is 12,200 (without eosinophilia); his CPK is normal.

• The most likely diagnosis is:


• A 38-year-old man presents with fever and an abscess on his

right arm. The lesion is very firm and is surrounded by

erythema. He has several other new abscesses.

• What would you recommend

- Do you need to I & D?

- Should you obtain cultures?

- Do you need antibiotics?

MRSA Soft Tissue Infection


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MRSA Soft Tissue Infection

Structure of Gram-Positive Bacteria

Cell WallCell Membrane

Penicillin Binding Proteins

DNA


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Beta-Lactams: Mechanism of Action



DNA

Beta-Lactam

Transpeptidation

Carboxypeptidation



Cell Wall Synthesis

DNA

Beta-Lactam

Methicillin-Susceptible Staphylococcus aureus

Nafcillin



DNA

mecA

Staphylococcus aureus: Methicillin Resistance


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Therapy for CA-MRSA Skin & Soft Tissue Infection2010 IDSA Practice Guidelines

• Simple Abscess or Boil

- Incision and Drainage

• Complicated Abscess*

- Incision and drainage + antimicrobial therapy

• Purulent Cellulitis (in absence of a drainable abscess)

- Empiric therapy for CA-MRSA

• Nonpurulent Cellulitis (and no abscess)

- Empiric therapy for beta-hemolytic streptococci

From: Liu C, et al. Clin Infect Dis. 2011:52:1-38.

*Complicated Abscess: multiple sites, rapid progression, associated cellulitis, systemic

symptoms, major comorbidity, extremes of age, hard area to I & D, failure with I &D

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10

20

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40

50

Treatment Failure (at day 7)

New Lesions (within 30 days)

27 28

17

9Patients (%)

I & D Alone I & D + TMP-SMX

Incision and Drainage +/- TMP-SMX for CA-MRSA Abscess

Study Design Treatment Failures

Source: Schmitz GR, et al. Ann Emerg Med. 2010;56:283-7.

• Methods

- 212 adults randomized

- 190 had F/U at day 7

- 96 had F/U at day 30

- All with uncomplicated CA-MRSA abscess

- Setting: emergency room

• Treatment Arms

- I & D + Placebo: 2 bid x 7d

- I & D + TMP-SMX: 2 DS bid x 7d

• Follow-Up

- Recheck at days 2 and 7

P = 0.12 P = 0.02

0

10

20

30

40

50

Treatment Success at Day 7

80

26

Patients (%)

I & D Needle Aspiration

Incision and Drainage vs Ultrasound Guided Needle Aspiration for CA-MRSA Abscess

Study Design Clinical Cure Rates

Source: Gaspari RJ, et al. Ann Emerg Med. 2011;January 14 [Epub ahead of print].

• Methods

- 101adults randomized

- All with uncomplicated CA-MRSA abscess

- Setting: emergency room

• Treatment Arms

- I & D

- US-Guided Needle Aspiration

- All received TMP-SMX +/- Cephalexin

• Follow-Up

- At 48 hours and day 7


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• Empiric Therapy for Out-Patient Management

- TMP-SMX: 1-2 DS tabs PO BID

- Clindamycin: 300-450 mg PO TID

- Doxycycline: 100 mg PO BID

- Minocycline: 200 mg x1, then 100 mg PO BID

- Linezolid: 600 mg PO BID

• If Also Covering for Group A Streptococcus

- TMP-SMX + Amoxicillin: 500 mg PO TID

- Clindamycin

- Doxycycline/Minocycline + Amoxicillin: 500 mg PO TID

- Linezolid



• Empiric Therapy for Hospitalized Patient

- Vancomycin: 15-20 mg/kd IV q 8-12 h

- Linezolid: 600 mg IV or PO BID

- Daptomycin: 4 mg/kg IV QD

- Telavancin: 10 mg/kg IV QD

- Clindamycin: 600 mg IV or PO TID


Vancomycin: Mechanism of Action

VancomycinCell Wall Synthesis

DNA


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Daptomycin: Mechanism of Action

Daptomycin

DNA

K+Ca2+

1. Ca2+-Dependent Binding to Cell Membrane

2. Membrane Depolarization and K+ Efflux

Cell Membrane

K+

1

2

Altered Penicillin

Binding Protein

Linezolid: Mechanism of Action

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SfMet-tRNA

50 S RibosomeLinezolid

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S

70 S Initiation Complex

30 S Ribosome

DNA

Televancin: Dual Mechanism of Action

Televancin

DNA

Televancin


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• A 45-year-old woman with poorly controlled IDDM had facial and periorbital swelling for 3-4 days. On the day of admission she was unable to open her right eye. On admission WBC= 22,000 (84% neutrophils and bands) (blood pH, 7.22; bicarbonate, 8 mmol/liter).



From: Rupp ME. N Engl J Med 1995;333:564.

• A 62-year-old man with chronic alcoholism and cirrhosis present with fever and multiple new blisters on his lower extremities. He just returned from a trip to New Orleans and he had abundant seafood on his trip, including raw oysters. He is hypotensive.


Case History: Hazard on the Half Shell



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Necrotizing Skin & Soft Tissue InfectionsDiagnostic Clues

• Bullous lesions

• Dark discoloration (blue/purple/grey)

• Subcutaneous gas

• Painful area that becomes anesthetic

• Systemic toxicity

• Rapidly advancing lesion

Necrotizing FasciitisLaboratory Predictive Factors

• Admission WBC > 14 x 109/L

• Serum Sodium < 135 mmol/L

• BUN > 15 mg/dl

From: Wall DB, et al. J Am Coll Surg 2000;179:17-2.

• A 33-year-old woman living in Washington State is bitten on her

hand by her cat while trying to break up a fight between her cat

and dog. One day later her wound is red and painful and she

comes to the ER for evaluation. Which of the following is TRUE?

1. Her risk of getting rabies from this cat bite is about 2%

2. Cat bites become infected more often than dog bites

3. Bartonella is the most likely cause of the infection

4. Pseudomonas is the most likely cause of the infection

Case History: Animal Bite


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Microbiology of Infected Cat Bites

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Pasteurella sp.

Streptococcus sp.

Staphylococcus sp.

Moraxella sp.

Fusobacterium sp.

Bacteroides sp.

Porphyromonas

Culture Results (%), N = 57

Aerobes

Anaerobes

From: Talan DA, et al. NEJM 1999;340:85-92.

Case History: Question

• A 29-year-old is bitten by a dog on his hand while trying to break

up a dog fight between 2 pets. This took place in Seattle.

• Which of the following is TRUE regarding dog bites and

infection?

1. His risk of getting rabies from this dog bite is about 5%

2. Pseudomonas cani is a common pathogen

3. Optimal prophylaxis is Amoxicillin

4. Pasturella is one of the most commonly

isolated organisms

Microbiology of Infected Dog Bites

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Pasteurella sp.

Streptococcus sp.

Staphylococcus sp.

Neisseria sp.

Fusobacterium sp.

Bacteroides sp.

Porphyromonas

Culture Results (%), N = 50

Aerobes

Anaerobes

From: Talan DA, et al. NEJM 1999;340:85-92.


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Dog & Cat Bites Wound Infections: Therapy

• Therapy (Oral)

- Amoxicillin-CA x 7-14 days

• Therapy (Intravenous

- Ampicillin-sulbactam

- Ertapenem

• Therapy (Penicillin-Allergic)

- Clindamycin + Fluoroquinolone

• This 36-year-old man is admitted to intensive care unit 3 days after suffering a dog bite on his right knee. He has a BP = 85/60, he has diffuse purpura, and lab studies that show evidence of DIC. Tragically, he died 6 hours after admission to the ICU.

• Which organism most likely caused this infection?

1. Moraxella catarrhalis2. Pasteurella canis3. Capnocytophaga canimorus (DF-2)4. Pseudomonas aeruginosa


Cat Scratch Disease: Bartonella henselae


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From: Bass JW et al. Pediatr Infect Dis 1998;17:447-52.

Cat Scratch Disease: Azithromycin Therapy

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Patients %

Day 30: 80% Decrease in Lymph Node Volume

Azithromycin (N=14) Placebo (N=15)

50%

7%

• 52-year-old previously healthy woman presents to urgent

care following a macaque monkey bite? The patient

works as a researcher at a primate laboratory at the UW.

• What oral antimicrobial therapy would you recommend?

1. Amoxicillin-clavulanic acid + Doxycycline

2. Amoxicilin-clavulanic acid + Valacyclovir

3. Moxifloxacin + Interferon-alpha

4. Moxifloxacin + Ribavirin

Case History

B Virus (Ceropithecine herpesvirus 1)

• Endemic among macaque monkeys

• Shedding from oral, conjunctival, or genital mucosa

• Incubation: 2-35 days (most 5-21 days after exposure)

• Clinical infection: vesicular rash, peripheral NS, CNS

• Mortality rate if untreated: 80%

From: Cohen JI. Clin Infect Dis 2002;35:1191-203.

Documents

Management of Skin & Soft Tissue Infections of Skin & Soft Tissue Infections David H. Spach, MD Professor of Medicine Division of Infectious Diseases University of Washington, Seattle