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 and
understand the basics of initial treatment
• Understand the evidence behind treatment of purulent
skin and soft tissue infections
POLL EVERYWHERE
• Text BenA860 to 22333 for interactive polling
• When the questions come up, simply text the
letter associated with your answer to that same
number (22333)
Skin and Soft Tissue Infections
PurulentNon-Purulent
Erysipelas Cellulitis Necrotizing
FasciitisAbscess Furuncle Carbuncle
Importance of distinction:
• Affects likely microbiology, treatment, and follow upPublic 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=2~150
http://healthh.com/wp-content/uploads/2014/05/erysipelas-pictures-2.jpg
Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
NON-PURULENT SSTI:
CELLULITIS/ERYSIPELAS
Cellulitis
• Infection involving deeper dermis and subcutaneous fat
• Border is less demarcated, onset is more indolent
• Essentially evaluated and treated the same as erysipelas
• Coverage for beta-hemolytic Strep is required
• Whether MSSA coverage is needed is debated
https://www.uptodate.com/contents/image?imageKey=ID%2F110605&topicKey=ID%2F110529&source=outline_link&search=cellulitis&selectedTitle=2~150
Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
NON-PURULENT SSTI:
CELLULITIS/ERYSIPELAS
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
• IDSA Guidelines:
• ‘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
WHAT COVERAGE IS NEEDED FOR
ERYSIPELAS AND CELLULITIS?
• Historically we have worried about beta-hemolytic Strep, MRSA, and MSSA for skin and soft tissue infections
• Strep coverage is always required for non-purulent SSTIs
• Therefore, when deciding on antibiotics for non-purulent skin and soft tissue infections, the questions are:
• Do I need MRSA coverage?
• Do I need MSSA coverage?
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
CONSIDERING MRSA COVERAGE
IN CELLULITIS
• Purulence noted
• Penetrating trauma
• Including IV drug use
• Open wound or underlying hardware
• Evidence of MRSA infection elsewhere
• Lack of response to beta-lactam therapy
• Not necessarily based on appearance
• Severe systemic symptoms
Clinical Infectious Diseases, Volume 59, Issue 2, 15 July 2014, Pages e10–e52,
WHAT COVERAGE IS NEEDED?
What about MSSA?
• Studies cited above have included Strep and MSSA coverage in the control groups
• No much data for regimens only covering Strep
• Per guidelines, ‘many clinicians could include coverage against MSSA (weak recommendation, low evidence)’
• Some first line regimens per IDSA guidelines only cover Strep
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
• For cellulitis, would not be faulted for including MSSA coverage
Clinical Infectious Diseases, Volume 59, Issue 2, 15 July 2014, Pages e10–e52,
NON-PURULENT SSTI:
CELLULITIS/ERYSIPELAS
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
Erysipelas Cellulitis Necrotizing
Fasciitis
What about TMP/SMX or doxycycline?• Efficacy against beta-hemolytic Strep is not well established
NON-PURULENT SSTI:
CELLULITIS/ERYSIPELAS
Guideline recommended oral treatment for mild
infections
Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
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 SSTI:
CELLULITIS/ERYSIPELAS
Guideline recommended IV treatment for
moderate non-purulent SSTI
Resistance rate
of 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
Erysipelas Cellulitis Necrotizing
Fasciitis
NON-PURULENT SSTI:
CELLULITIS/ERYSIPELAS
Guideline recommended IV treatment for
moderate non-purulent SSTI
Resistance rate
of 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
Erysipelas Cellulitis Necrotizing
Fasciitis
Medicine (Baltimore). 2010 Jul;89(4):217-26. doi: 10.1097/MD.0b013e3181e8d635.
DURATION OF THERAPY
• Uncomplicated cellulitis:
• IDSA Guidelines: ‘Recommended duration of antimicrobial therapy is 5 days, but treatment should be extended if the infection has not improved within this time period (strong recommendation, high quality evidence)
• Evidence: RCT showed 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
• Caveat: this study used only levofloxacin
Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
Arch Intern Med. 2004 Aug 9-23;164(15):1669-74.
ADJUNCTIVE THERAPIES FOR
CELLULITIS
• Limiting edema
• Leg elevation
• Look for portal of entry
• Fissuring, scaling, or maceration between toes
• Onychomycosis, psoriasis, etc
• 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
• Erythema, hyperpigmentation,
serous drainage, desquamation
• Nontender, no systemic signs,
usually bilateral
• Contact dermatitis
• Lymphedema
Cleveland Clinic Journal of Medicine. 2012 August;79(8):547-552
• 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,
disoriented, and lethargic. His WBC was 20.1.
Maxillofacial CT is seen below. What empiric
regimen should be started?
• Answers on following
slide
Skin and Soft Tissue Infections
PurulentNon-Purulent
Erysipelas Cellulitis Necrotizing
FasciitisAbscess Furuncle Carbuncle
Importance of distinction:
• Affects likely microbiology, treatment, and follow up
NON-PURULENT SSTI:
NECROTIZING INFECTIONS
Necrotizing fasciitis
• Severe, rapidly progressing, life threatening soft tissue
infection
• Often starts with skin lesion from minor trauma
• Exam may show blisters, purple discoloration, crepitus
• Patients are usually ‘toxic’
• Surgical emergency
Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
https://www.jyi.org/2002-may/2002/5/23/when-bacteria-go-bad-the-case-of-necrotizing-fasciitis
Guberman and Faroqi. Podiatry today, volume 24, issue 9, September 2011.
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
Erysipelas Cellulitis Necrotizing
Fasciitis
NON-PURULENT SSTI:
NECROTIZING INFECTIONS Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
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
NON-PURULENT SSTI:
NECROTIZING INFECTIONS Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
Diagnosis
• Definitive diagnosis is with surgery
• ‘dishwater gray’ tissues
• 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
NON-PURULENT SSTI:
NECROTIZING INFECTIONS Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
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
NON-PURULENT SSTI:
NECROTIZING INFECTIONS Non-Purulent
Erysipelas Cellulitis Necrotizing
Fasciitis
Skin and Soft Tissue Infections
PurulentNon-Purulent
Erysipelas Cellulitis Necrotizing
FasciitisAbscess Furuncle Carbuncle
Importance of distinction:
• Affects likely microbiology, treatment, and follow up
DEFINITIONS (PURULENT)
Abscess
• Collections of pus within the dermis and deeper skin tissues
• Painful, tender, and fluctuant
Furuncles
• Infections of the hair follicle with pus down to the subcutaneous tissues
• Aka ‘boils’
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)
• Occasionally see Strep, GNRs but we don’t often
empirically cover for these
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
UIHC ANTIBIOGRAM
TREATMENT OF
UNCOMPLICATED ABSCESSES
Group Clindamycin TMP/SMX Placebo
Cured/
Total
%
(95% CI)
Cured/
Total
%
(95% CI)
Cured/
Total
%
(95% CI)
Intention to treat 221/266 83.1%
(78.3-87.9)
215/263 81.7%
(76.8-86.7)
177/257 68.9%
(62.9-74.9)
Population available
for evaluation
221/238 92.9%
(89.3-96.4)
215/232 92.7%
(89.0-96.3)
177/220 80.5%
(74.8-86.1)
N Engl J Med 2017; 376:2545-2555
TREATMENT OF ABSCESSES
BMJ Open. 2018 Feb 6;8(2)
Treatment Failure in 1 month
OR 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
TO PACK OR NOT TO PACK
Abscesses < 5cm, immunocompetent Packing
N = 23
No packing
N= 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
QUESTIONS?