skin 15: necrotizing fasciitis and toxic shock-like syndrome

Question 1

necrotizing fasciitis (NF)

Answer 1

An uncommon life-threatening infection of subcutaneous tissue which results in necrosis of fascia, fat, tissues and vasculature with or without secondary involvement of skin and skeletal muscle but with severe systemic illness including one or more of following: shock, DIC, organ failure.

Question 2

NF forms:

Answer 2

Type I: Polymicrobic (mixed) Form caused by facultative anaerobes and anaerobes

Type II: Monomicrobial Form

Type III: Clostridial myonecrosis, AKA Gas Gangrene

Question 3

Polymicrobic (mixed) Form (Type I) Number of etiologic agents involved ranges from 5-15 and include:

Answer 3

G+ cocci: Streptococci, Staphylococci.
Numerous facultative anaerobic and/or obligate anaerobic, G- rods (e.g., Escherichia coli, Pseudomonas sp., etc).
A variant of type I is saltwater necrotizing fasciitis caused by the salt water agents, the vibrios.

Question 4

Predisposing factors to NF Type I (FYI):

Answer 4

surgical procedure (esp. the bowel),
vulvovaginal infections.,
infections involving ulcers, abscesses, IVDU

Question 5

Monomicrobial Form (Type II): agents

Answer 5

G+ cocci:

• GAS – invasive GAS (serotype M1)
• GBS
• Peptostreptococcus sp.
• S. aureus
• mixed infections - both GAS and S. aureus

obligate anaerobic, G+ rods:
Clostridium perfringens, type A; C. septicum.

obligate anaerobic, G- rods (e.g., Bacteroides sp.).

Question 6

Predisposing factors for NF Type II is mainly underlying disease (FYI):

Answer 6

arteriosclerotic vascular disease,
venous insufficiency,
diabetes.

Question 7

NF Initial Presentation (within first 24 hours):

location ??

Answer 7

Location, regardless of etiology, is usually the extremities (esp. LE)

• Patient is acutely ill and in severe pain*
• A slowly advancing cellulitis with severe, excoriating pain (while pain is subjective, the elevated level/intensity of pain is unusual for cellulitis)*

Question 8

NF “cellulitis” characteristics

Answer 8

Involved skin progresses from tender and warm–> shiny with diffuse
symmetrical swelling (erythema, edematous).
Infection rapidly spreads along fascial planes undermining of adjacent tissues.
A broad erythematous tract in skin along the fascial plane route may be
evident.
Muscle and overlying skin are spared.

Question 9

NF Days 2-4 - During the next 24-48 hours, the infection can also progress:

Answer 9

The erythema of the involved skin progresses from red->purple->blue and blisters/bullae containing clear yellow fluid appear.
-subQ tissues are firm and fascial planes and muscle groups cannot be discerned by palpation. Infection to the depth of the enveloping fascia generally involves muscle (bacterial myositis + destruction of muscle).

Question 10

NF: ?? may occur 4 - 5 days after the initial erythema, the areas become gangrene.
what is present in about 60% of cases??
systemic symptoms may include??

Answer 10

Anesthesia in the affected area

• Severe pain, blisters, bullae, and anesthesia are due to occluded blood vessels.
• Bacteremia is present in most (~ 60% of) cases.
• Marked systemic symptoms are present, may include shock and organ failure.

Question 11

NF complications

Answer 11

Streptococci, especially GAS – STSS.
Gram-negative organisms: Endotoxic shock, DIC.
Clostridial toxemia

Question 12

It is necessary to distinguish between cellulitis, NF, and myonecrosis because:
??

Answer 12

cellulitis is amenable to antimicrobial therapy.
NF and myonecrosis require both:
a. surgical intervention
b. antimicrobial therapy.

Question 13

NF clues

Answer 13

Abrupt onset of severe, excruciating pain while subjective/not quantifiable, NF is 10 of 10
Systemic toxicity: often AMS (confusion).
Hard, wooden feel of subcutaneous tissue, extending beyond the area of apparent skin involvement – due to the presence of gas in tissues. Muscle groups cannot be discerned by palpation
Utilizing palpation of hard tissues, X-ray, CT-scan, MRI to detect gas, determine the extent of infection – necessity for surgery – see below.
If anaerobes are involved a distinctive odor of putrefaction is usually present.

Question 14

NF more clues: Appearance of the tissue at surgery:

Answer 14

Fascia is swollen and dull gray.
Deep dissection reveals absence of pus, only a thin, brownish-colored (“dish-water”) exudate.
Extensive undermining of surrounding tissue is present.

Question 15

cellulitis vs fasciitis response to abx tx

Answer 15

Patients with fasciitis fail to respond to antimicrobial therapy but with appropriate antimicrobial therapy for cellulitis, the patient usually improve in 24-48 h.

Question 16

NF lab specimens to get:

Answer 16

blood.
deep tissue specimens from affected areas taken during surgery
Warning: Gram-stain and culture from a superficial skin lesion (if present) is not usually indicative of the deep tissue infection.

Question 17

NF lab tests to do

Answer 17

Gs, Cx/Sn

results will often ID the true etiologic agent

Question 18

NF: Approximate identification of etiologic agent(s) is required to select appropriate
antibiotics:

Answer 18

G+ cocci in chains indicate GAS (aerotolerant anaerobe) or
Peptostreptococcus sp. (obligate anaerobe).
G+ cocci in clusters indicates S. aureus (facultative anaerobe).
Mixed flora suggests a polymicrobic infection.

Question 19

In patients with NF and myositis caused by GAS, ?? is often (~ 50% of time) present.

Answer 19

STSS!

Question 20

NF tx

Answer 20

Bold resection of all necrotic material and incise fascial planes until the entire extent of infection is exposed (to the full extent of the gas penetration, not the area visibly affected)

Abx tx, based upon ID of etiologic agent(s), is prolonged (23 weeks).
-For GAS, PCN is drug of choice, but treatment failure can occur due to physiological/mechanical issues (failure of blood/vasc. to deliver PCN).

Hyperbaric oxygen.

Question 21

NF mortality

Answer 21

Overall is high (20-30%) due to systemic involvement.
For GAS is high (30-60%), despite absence of underlying disease, use of antibiotics, dialysis, ventilators, intravenous fluids, modern surgical techniques.

Question 22

Streptococcal Toxic Shock (STSS): hallmarks

Answer 22

Early onset of shock and organ failure.

Isolation of streptococci from a normally sterile site

Question 23

STSS is ??

caused by ??

Answer 23

Non-menstrual toxic shock syndrome caused by lysogenized strains of S. pyogenes (GAS)
usually invasive GAS (serotype M1).
Caused by strains that elaborate SPEs - superantigens

Question 24

STSS
occurs where??
POE??

Answer 24

Skin or soft tissue infection, necrotizing fasciitis, myositis (necrotizing fasciitis with or without myonecrosis is present @ 50% of the time).

POE is usually skin or mucous membrane (throat or vaginal tract).

Question 25

STSS pt. with soft tissue infections tend to be ??

Answer 25

younger and with no underlying illness.

Question 26

Elderly patients with STSS tend to have ??

Answer 26

GAS bacteremia with no septic (soft tissue) focus, but have underlying illness (FYI):

liver disease, alcoholism, diabetes, arteriosclerotic vascular disease.

Question 27

Conditions required for STSS, same as per ??

Answer 27

Scarlet fever:

• Lack of neutralizing immunity in host: For STSS caused by S. pyogenes: the presence or absence of immunity to specific M-types (1, 3, 12, 28) as well as to SPEs determines the clinical syndrome, outcome of infection.
• SPEs are superantigens*

Question 28

STSS symptoms which occur often 1- 2 d before the onset of other symptoms:

Answer 28

fever > 38.9oC (102oF) and chills
malaise;
myalgia;
nausea and vomiting
Profuse, watery diarrhea occurs for about 1 day.

Question 29

what STSS symptoms happen next?

Answer 29

abrupt onset of severe pain increasing to excruciating level which precedes tenderness or physical findings and usually affects the extremities (Only if there is a focal infection, remember this disease can occur with bacteremia alone).
-Intense mucous membrane erythema/hyperemia occurs with STSS.

Question 30

Other STSS symptoms (at the time of or within 48 hours after admission):

Answer 30

Hypotensive shock and multi organ failure: Renal failure, CNS involvement->AMS, pulm. involvement->ARDS, Hepatic insufficiency.

Bacteremia.
DIC.
Rash

Question 31

STSS rash

Answer 31

a diffuse macular erythroderma which evolves into a scarlatiniform rash, which desquamates (particularly on palms & soles) 1- 2 w after the onset of S&S.

Question 32

in STSS pt., ?? and/or ?? frequently (~50% of the time) occur.

dx based on ??
lab signs ?

Answer 32

NF, myositis

pts s/s
Gs, Cx/Sn of throat, blood, skin lesion/site specimens,

Lab signs: Profound left-shift in granulocyte series (band forms, AKA immature granulocytes are present in peripheral circulation).

Question 33

tx of STSS

Answer 33

penicillin plus clindamycin

Question 34

tx of STSS and NF caused by GAS:

Answer 34

Penicillin plus clindamycin.
+Bold resection of all necrotic material and incise fascial planes until the entire extent of infection is exposed (to the full extent of the gas penetration, not just the area visibly affected).