4/21 Soft Tissue Infections - Corbett

Question 1

skin defenses

Answer 1

• epidermal barrier
• normal skin microflora
• antimicrobial peptides
• low temp
• low pH

→→→ skin inf renerally requires BREACH of epi barrier (micro or macro)

Question 2

skin inf in kids and adults

Answer 2

children

• impetigo

adults

• erysipelas
• cellulitis
• abscess
• necrotizing soft tissue inf

Question 3

impetigo

Answer 3

common in children <5yo

superficial (epidermis) non-follicular pustules

• small painless vesicles with purulent material drying into “golden/honey crust” after rupture
• minimal systemic sx
• no scarring

bacterial

• Staph aureus: bullous (exfoliative toxin) and non-bullous
• beta-hemolytic Strep

tx: wound care, keep away from others, antibiotics

Question 4

erysipelas

Answer 4

superficial (epidermis and v upper dermis), non-purulent, non-necrotizing inf of upper dermis

adults > 60yo

risk: immunocompromised

RAPID SPREAD w lymphatic involvement and lymphangitis

• starts small as bright red/shiny/edematous/indurated lesions
• well defined w slightly raised borders

lower limb, often unilateral

bacterial etiology

• group A beta-hemolytic Strep
• Staph aureus

tx:

• oral antibiotics (depending on Strep or Staph)
• prevent edema (diuretics, limb elevation, compr stockings)
• keep skin hydrated
• treat dermatophytic inf

Question 5

cellulitis

Answer 5

• acute, spreading, nonnecrotizing inf involving deeper dermis and subcut fat
• purulent drainage in absence of drainable abscess**
  
  • need systemic abx
  • but if you have abscess, NEED TO DRAIN

bacterial etiology:

• beta-hemolytic Strep
• Staph less common

risks: disruption of cutaneous skin, lymphedema, LE surgical operations, obesity (fat is poorly vascularized)

Question 6

cellulitis presentation

cellulitis tx

Answer 6

tenderness, warmth, erythema

assess for evidence of:

• abscess (bc if so, need drainage)
• necrotizing inf (abx not enough - need debridement)

culture is HARD, so begin empiric tx

• nonpurulent cellulitis
  
  • empiric tx for group A beta-hemolytic Strep
  • dephalexin, dicloxacillin, clindamycin
• ​purulent cellulitis
  
  • empiric tx for CA-MRSA
  • clindamycin, trimethoprim-sulfamethoxazole, doxycycline or linezolid

Question 7

abscess

Answer 7

collection of pus within dermix or subcut tissue

present as nodules with flucuence and surrounding erythema

Staph aureus

tx: incision and drainage

Question 8

sbscess

folliculitis

furuncle

carbunce

Answer 8

Question 9

necrotizing soft tissue infections

Answer 9

“flesh eating bacteria”

• bacterial toxins damage endothelium → incr microvasc permeability & tissue edema → impaired cap flow
• extensive small vessel thrombosis
  
  • local hypercoagulability
  • platelet-neutrophil plugging of vessels
  • incr interstitial pressure

involve any of soft tissue layers (incl dermix, subcut tissue, superficial or deep fascia and muscle)

SURGICAL EMERGENCY

Question 10

microbiology for type I, II, III infections

Answer 10

Question 11

type I infection

Answer 11

Enterococcus species

bacterioides species

E coli

Question 12

type II infection

organism

how infection in healthy people???

Answer 12

group A beta-hemolytic strep

how can GABHS cause invasive inf in healthy people?

• existent reservoirs of bacteria
• effective combo of virulence factors: M protein, SpeB, Sda1
• can survive intracellularly and elude immune surveillance
• induction of T cell homing to site of inf (superantigen)

Question 13

Scalded Skin Syndrome

Answer 13

preceded by Staph aureus inf

• epidermolytic toxins: ETA and ETB
• toxins can be local or disseminated in bloodstream
• act on stratum granulosum
• • Nikolsky sign (sep of epidermal layer w stroking of skin)

at risk: newborns, infants, immunocomp adults