Appenheimer, Ben - Skin and Soft Tissue Infections · Microbiology • Predominantly beta-hemolytic Strepspecies •i.e. Group A Strep(aka Strep pyogenes) •Staphaureus is a much

3/25/2019

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Ben Appenheimer, MD

Assistant Professor

Division of Infectious Diseases

4/2/19

*No disclosures or conflicts of interest

SKIN AND SOFT TISSUE INFECTIONS

OBJECTIVES• Understand the difference between purulent and non-

purulent skin and soft tissue infections (SSTIs)

• Understand how this difference affects microbiology and treatment

• Learn how to identify necrotizing fasciitis, know the etiologic organisms, and understand the basics of treatment

• Understand the evidence behind treatment of purulent skin and soft tissue infections

POLL EVERYWHERE• Text BenA860 to 22333 for interactive polling

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Skin and Soft Tissue Infections

PurulentNon-Purulent

Erysipelas Cellulitis NecrotizingFasciitis

Abscess Furuncle Carbuncle

Importance of distinction: • Affects likely microbiology, treatment, and follow up

Public Health Image Library, CDC

NON-PURULENT SSTI: CELLULITIS/ERYSIPELAS

Erysipelas

• Generally refers to infection limited to upper dermis

• Some use it synonymously with cellulitis

• Well-demarcated, rapid onset fevers, chills, erythema

• Almost exclusively caused by beta-hemolytic Strep

https://www.uptodate.com/contents/image?imageKey=ID%2F110605&topicKey=ID%2F110529&source=outline_link&search=cellulitis&selectedTitle=2~150http://healthh.com/wp-content/uploads/2014/05/erysipelas-pictures-2.jpg

Non-Purulent



Cellulitis

• Infection involving deeper dermis and subcutaneous fat

• Border is less demarcated, onset is more indolent

• Essentially evaluated and treated the same as erysipelas

https://www.uptodate.com/contents/image?imageKey=ID%2F110605&topicKey=ID%2F110529&source=outline_link&search=cellulitis&selectedTitle=2~150

Non-Purulent


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Microbiology• Predominantly beta-hemolytic Strep species

• i.e. Group A Strep (aka Strep pyogenes)

• Staph aureus is a much less common cause of non-purulent cellulitis

• Evidence

• ‘Combined data from specimen cultures, serologic studies, and other methods suggests that the vast majority of these infections arise from Streptococci’

Open Forum Infectious Diseases, Volume 3, Issue 1, 1 January 2016, ofv181

CONSIDERING MRSA COVERAGE IN CELLULITIS • Purulence noted

• Penetrating trauma

• Including IV drug use

• Open wound

• Evidence of MRSA infection elsewhere

• Lack of response to beta-lactam therapy

• Not necessarily based on appearance

Clinical Infectious Diseases, Volume 59, Issue 2, 15 July 2014, Pages e10–e52,

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WHAT COVERAGE IS NEEDED?

Is MRSA coverage needed?

What about in the inpatient setting?

• One hospital looked at response to oxacillin or cefazolin in treatment of ‘non-culturable’ cellulitis

• 116/121 (95.8%) had clinical response without MRSA coverage

Cephalexin alone

Cephalexin + TMP/SMX

95% CI P value

Pallin et al 2013 60/73 (82%) 62/73 (85%) -9.3% to 15% 0.66

Moran et al 2017 165/193 (85.5%) 182/218 (83.5%) -9.7% to 5.7% 0.50

WHAT COVERAGE IS NEEDED?What about MSSA?

• Studies cited above have included Strep and MSSA coverage in the control groups

• ie cefazolin, cephalexin, oxacillin, etc

• Prophylaxis for recurrent cellulitis rarely includes MSSA coverage

• Per guidelines, ‘many clinicians could include coverage against MSSA (weak recommendation, low evidence)’

My take:

• For presentations that are classic for erysipelas (ie rapid onset, well-demarcated erythema, no signs of deep fluid collection, no trauma or wound), I often focus my coverage on Strep pyogenes with either penicillin or amoxicillin



Guideline recommended oral treatment for mild infections

Dosing Resistance rate of Group A Strep

Notes

Penicillin VK 500mg QID 0% Narrowest spectrum

Amoxicillin 500mg TID 0% 3x daily dosing

Cephalexin 500mg QID 0% Only needed if MSSA coverage desired

Dicloxacillin 500mg QID 0% Only needed if MSSA coverage desired

Clindamycin 300mg QID ~5% Some resistance, some Staph coverage

Non-Purulent


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What about TMP/SMX or doxycycline?• Efficacy against beta-hemolytic Strep is not well established


Guideline recommended oral treatment for mild infections

Non-Purulent


Dosing Resistance rate of Group A Strep

Notes

Penicillin VK 500mg QID 0% Narrowest spectrum

Amoxicillin 500mg TID 0% 3x daily dosing

Cephalexin 500mg QID 0% Only needed if MSSA coverage desired

Dicloxacillin 500mg QID 0% Only needed if MSSA coverage desired

Clindamycin 300mg QID ~5% Some resistance, some Staph coverage


Guideline recommended IV treatment for moderate non-purulent SSTI

Resistance rateof Group A Strep

Notes

Penicillin G 0% Narrowest spectrum, continuous infusion

Cefazolin 0% 3x daily dosing, covers MSSA

Ceftriaxone 0% Once daily, broader than needed (ie GNR coverage)

Clindamycin ~5% Occasionally covers Staph

Non-Purulent



Guideline recommended IV treatment for moderate non-purulent SSTI

Resistance rateof Group A Strep

Notes

Penicillin G 0% Narrowest spectrum, continuous infusion

Cefazolin 0% 3x daily dosing, covers MSSA

Ceftriaxone 0% Once daily, broader than needed (ie GNR coverage)

Clindamycin ~5% Occasionally covers Staph

What about Vancomycin?• Relatively weak Strep drug. Technically covers it, but not well

Non-Purulent


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Medicine (Baltimore). 2010 Jul;89(4):217-26. doi: 10.1097/MD.0b013e3181e8d635.

DURATION OF THERAPY• Uncomplicated cellulitis:

• If symptoms have improved by 5 days, 5 day course is as effective as a 10 day course• Clinical manifestations did not need to be fully resolved

• Randomized at day 5 as long as at least minimal improvement had occurred

• Caveat: this study used levofloxacin, not often used for cellulitis at this time

• Exclusion criteria: severe sepsis, bacteremia, deep soft tissue infection, debridement, bite wounds, diabetic foot ulcer, etc

Non-Purulent


Arch Intern Med. 2004 Aug 9-23;164(15):1669-74.

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ADJUNCTIVE THERAPIES FOR CELLULITIS• Leg elevation

• Look for portal of entry

• Fissuring, scaling, or maceration between toes

• Onychomycosis

• Prednisone

• Per IDSA, ‘can consider 40mg PO x 7 days in non-diabetic patients’

• RCT with 108 patients showed more rapid clinical resolution without change in relapse or recurrence rates

• Haven’t seen this done clinically very often

Scand J Infect Dis. 1997;29(4):377-82.

CELLULITIS MIMICS• Stasis dermatitis

• Nontender, no systemic signs, usually bilateral

• Erythema, hyperpigmentation, serous drainage, desquamation

• Contact dermatitis

• Lymphedema

Cleveland Clinic Journal of Medicine. 2012 August;79(8):547-552

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• 38 y/o with h/o untreated HCV who presents to the ED with left periorbital swelling, erythema, and pain. This started shortly after a fall where he hit his eye on a well pump. Over the next 24 hours he noticed progressive swelling, severe pain, and purplish discoloration. He was febrile up to 104.5. His WBC was 20.1. Maxillofacial CT is seen below. What empiric regimen should be started?

• Answers on following slide






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NON-PURULENT SSTI: NECROTIZING INFECTIONS

Necrotizing fasciitis

• Severe, rapidly progressing, life threatening soft tissue infection

• Exam may show blisters, purple discoloration, crepitus

• Patients are usually ‘toxic’

• Surgical emergency, requires broad spectrum antibiotics initially

Non-Purulent


NON-PURULENT SSTI: NECROTIZING INFECTIONS

Microbiology

• Variable

• Type I Necrotizing fasciitis• Polymicrobial (as in Fournier’s gangrene or

odontogenic infections)

• Mix of aerobic and anaerobic bacteria (including Clostridium perfringens)

• Type II necrotizing fasciitis• Monomicrobial

• Strep pyogenes infection

• Staph aureus

Non-Purulent


Pathogenesis

• Usually starts with skin lesion from some trauma

• Can be minor

• Often toxin-mediated

• Combine anti-toxin antibiotic when treating Strep necrotizing SSTI

NON-PURULENT SSTI: NECROTIZING INFECTIONS Non-Purulent


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Clinical manifestations

• Initial presentation is similar to cellulitis

• Progresses to include systemic toxicity

• High fevers, disorientation, lethargy

• Skin can become firm, necrotic (purple/black/gray), blister, and have crepitus

• Pain out of proportion to exam

• Very high mortality with Strep pyogenes• 30-70%

• Those who survive often have significant morbidity



Diagnosis

• Mainly clinical and surgical

• Severe pain disproportional to clinical findings

• Radiographs (CT is best) showing subcutaneous air are suggestive of necrotizing SSTIs

• If high suspicion, should not wait for imaging prior to surgical consult

• This is a relatively late finding

• Definitive diagnosis is with surgery

• ‘dishwater gray’ tissues



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Treatment• Immediate surgical consult for emergent

operative debridement• Often require multiple re-explorations

• Initially cover with broad spectrum antibiotics• As previously mentioned, microbiology can be variable

• Need to cover Strep, Staph (including MRSA), resistant GNRs, and anaerobes

• Once the organism is known, tailor therapy accordingly

• If Strep pyogenes, treat with penicillin and add clindamycin for toxin suppression









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DEFINITIONS (PURULENT)Abscess

• Collections of pus within the dermis and deeper skin tissues

• Painful, tender, and fluctuant

Furuncles• Aka ‘boils’

• Infections of the hair follicle with pus down to the subcutaneous tissues

Carbuncles• Infection involving several

adjacent follicles

https://www.uptodate.com/contents/image?imageKey=ID%2F110605&topicKey=ID%2F110529&source=outline_link&search=cellulitis&selectedTitle=2~150

Microbiology

• Most common: Staph aureus (MSSA and MRSA)

Antibiotics• Empiric therapy should target MRSA and MSSA

with narrowing after susceptibilities

• TMP/SMX or doxycycline

• Vancomycin

PURULENT SSTI

CID 2014:59 (15 July)https://www.uptodate.com/contents/image?imageKey=ID%2F53261&topicKey=ID%2F110529&source=outline_link&search=abscess&selectedTitle=4~126

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UIHC ANTIBIOGRAM

TREATMENT OF UNCOMPLICATED ABSCESSES

N Engl J Med 2017; 376:2545-2555

TREATMENT OF ABSCESSES

BMJ Open. 2018 Feb 6;8(2)

Treatment Failure in 1 monthOR 0.58 (0.37,0.90)

Recurrence or new lesion within 1 month

OR 0.48 (0.3, 0.77)

Recurrence or new lesion > 1 month

OR 0.64 (0.48, 0.85)

Favors Antibiotics Favors Control

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TO PACK OR NOT TO PACK

Abscesses < 5cm, immunocompetent PackingN = 23

No packingN= 25

RR, 95% CI P value

Re-intervention at 48 hours 4 5 1.3, (0.4 – 4.2) 0.72

Use of ibuprofen in first 48 hrs (600mg pills) 2.29 1.97 0.12

Use of oxycodone/APAP (pills) 3.1 0.91 0.03

Acad Emerg Med. 2009 May;16(5):470-3.

TAKE HOME POINTS• Most non-purulent skin and soft tissue infections are due

to beta-hemolytic Strep and empiric coverage should be targeted at these organisms

• Use beta-lactam antibiotics

• MRSA coverage is not necessary for non-purulent skin and soft tissue infections

• Unless there is penetrating trauma or open wound

• Relatively short course treatment can be considered for uncomplicated cases (ie 5 days)

• Be wary of ‘bilateral cellulitis’

TAKE HOME POINTS• If concerned for necrotizing fasciitis, call surgery and

cover broadly

• Imaging can show subcutaneous air but this is a late finding and is not sensitive for detecting nec fasc

• There is increasing evidence that patients benefit from anti-MRSA antibiotics after I & D

• TMP/SMX and doxycycline have highest susceptibility rates

• There is some question whether packing small abscesses after I&D provides any significant benefit

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QUESTIONS?

Documents

Appenheimer, Ben - Skin and Soft Tissue Infections · Microbiology • Predominantly beta-hemolytic Strepspecies •i.e. Group A Strep(aka Strep pyogenes) •Staphaureus is a much