Skin Infections B&B

Question 1

in impetigo, a superficial skin infection occurs in which neutrophils collect beneath the…

Answer 1

stratum corneum

macules —> papules —> rupture —> erosions —> “honey-colored” crust due to dried sebum

Question 2

contrast the 2 subtypes of impetigo

Answer 2

1. impetigo contagiosa (non-bullous): most common, face/extremities, caused by staph. aureus or strep. pyogenes —> honey-crusted lesions
2. bullous impetigo: bullous (blisters) form on trunk, always caused by staph. aureus strains with exfoliative toxin

Question 3

what allows some strains of staph. aureus to cause bullous impetigo, while others form non-bullous impetigo?

Answer 3

bullous impetigo = blisters form on trunk

staph. aureus strains with exfoliative toxin cleave desmoglein 1 complex (desmosome protein, links keratinocytes together) —> keratinocyte attachments are destroyed in stratum granulosum

fluid enters space, allowing bullous to form

[same toxin that causes scalded skin syndrome]

Question 4

which bacterial toxin is responsible for scalded skin syndrome?

Answer 4

colonization of skin with staph. aureus strains with exfoliative toxin —> diffuse erythema and skin peeling + fever

occurs 3-7 days after birth, damage is intra-epidermal so it heals completely with no scar

Question 5

erysipelas vs cellulitis

Answer 5

both caused by skin break/trauma that allows bacterial entry, but differ in layer of skin involvement

erysipelas: infection of superficial dermis (well-demarcated), elderly + children patients

cellulitis: infection of deep dermis (ill-defined), elderly patients

Question 6

erysipelas

Answer 6

skin infection caused by break in skin, occurs in superficial dermis

usually group A strep (S. pyogenes) —> acute fever, chills, rash with clear demarcation

Question 7

infection of superficial dermis, usually caused by Group A strep (S. pyogenes) with acute onset of fever/chills and rash with clear demarcation

Answer 7

erysipelas

Question 8

cellulitis is an infection of which layer of the skin? how does it present?

Answer 8

infection (caused by break in skin) of deep dermis + subcutaneous fat

caused by Group A strep (S. pyogenes) or S. Aureus —> slow onset of rash, focal pain, warmth

rash is ill-defined with spreading border

Question 9

infection of deep dermis and subcutaneous fat usually caused by Group A strep (S. pyogenes) or S. aureus, presenting with slow onset of focal pain/warm and rash with ill-defined/spreading borders

Answer 9

cellulitis

Question 10

in which layer of the skin do abscesses occur?

Answer 10

skin abscess: collection of pus in dermis or subcutaneous space

usually caused by staph. aureus

Question 11

Type 1 vs Type 2 necrotizing fasciitis

Answer 11

Type 1: polymicrobial (often anaerobes), occurs in diabetics/immunocompromised usually following surgery

Type 2: Group A strep (sometimes Staph), occurs in otherwise healthy people after skin injury