Skin III Flashcards
describe type I: polymicrobial necrotizing fasciitis/myonecrosis
- type I: polymicrobial
- due to both aerobic and anaerobic bacteria
- common following intra-abdominal surgery, in diabetics and in intravenous drug users
type II necrotizing fasciitis/myonecrosis is caused by ____
type II necrotizing fasciitis/myonecrosis is caused by S. pyogenes
describe the onset of necrotizing fasciitis/myonecrosis
sudden onset (as short as ~4 hours)
describe Clostridium perfringens
describe the virulence factor of Clostridium perfringens
- exotoxins:
- alpha toxin (lecinthinase)
C. perfringens requires ___, ____ and ____ conditions in order to grow
C. perfringens requires damaged, dead tissue and anaerobic conditions in order to grow
the culture of C. perfringens on blood agar would show a characteristic ___ zone of hemolysis
the culture of C. perfringens on blood agar would show a characteristic double zone of hemolysis
beta-hemolysis surrounded by a larger zone of alpha hemolysis
describe the purpose of culturing C. perfringens on egg-yolk agar (EYA)
lecithinase from C. perfringens forms opaque colonies on EYA
- lecithinase
- lecithinase degrades lecithin to insoluble diglycerides; positive reaction is white opaque zone around colonies
- lipase test:
- lipase degrades triglycerides into glycerol and FFAs
- positive reaction is a pearly, iridescent sheen on agar and colonies
the Nagler test is used to differentiate among _____
the Nagler test is used to differentiate among lecithinase-positive Clostridium spp.
describe the purpose of reverse CAMP test
describe crepitus
describe the clinical manifestations of staphylococcal scalded skin syndrome
- clinical:
- SSSS usually starts with fever and widespread redness of the skin
- within 24-48 hours fluid-filled blisters form
- these rupture easily, leaving an area that looks like a burn
describe the epidemiology of scalded skin syndrome
- occurs mostly in children younger than 5, particularly in neonates
- lifelong protective antibodies against staphylococcal exotoxins are usually acquired during childhood
in scalded skin syndrome, staphylococcal spp. release 2 ___ that bind to ___ and break it up
in scalded skin syndrome, staphylococcal spp. release 2 exotoxins that bind to desmoglein-1 and break it up
the most common cause of erythrasma is ____
the most common cause of erythrasma is Corynebacterium minutissimum
in erythrasma, ____ invade the ____
in erythrasma , Corynebacterium minutissimum invade the upper third of the stratum corneum
in erythrasma, infected skin glows ____
in erythrasma , infected skin glows coral-red under UV
the coral-red fluorescence is secondary to the production of porphyrin (heme metabolism)
favorable conditions for C. minutissimum are ___ and ___
which locations of the body have these conditions?
favorable conditions for C. minutissimum are heat and humidity
foot, groin, armpits, skinfolds, vaginal opening and the anus
erythrasma, caused by ___, affects mostly adults, especially those with ___ and those living in ____
erythrasma, caused by C. minutissimum, affects mostly adults, especially those with diabetes and those living in the tropics
erysipeloid is an ___ disease that is caused by ____
erysipeloid is an occupational disease that is caused by Erysipelothrix rhusipathiae
describe the clinical presentation of erysipeloid
risk factors for erysipeloid is contact with animals such as ___ and ___
risk factors for erysipeloid is contact with animals such as swine and fish
one of the pathogenetic mechanisms of erysipeloid is that it can cause ____
one of the pathogenetic mechanisms of erysipeloid is that it can cause endocarditis
in erysipeloid, the lesion has a ___ color with ___ borders
in erysipeloid, the lesion has a violet color with well-defined borders
describe the 3 important virulence factors of anthrax
-
edema toxin
- adenylate cyclase activity (fluid accumulation)
-
lethal factor
- stimulate macrophages to release pro-inflammatory cytokines
-
protective antigen
- most immunogenic
the most immunogenic virulence factor of anthrax is ____
the most immunogenic virulence factor of anthrax is the protective antigen
edema toxin, formed by anthrax, causes an increase in ____ activity which leads to ____
edema toxin, formed by anthrax, causes an increase in adenylate cyclase activity which leads to fluid accumulation
lethal factor, found in anthrax, stimulates ___ to release ____
lethal factor, found in anthrax, stimulates macrophages to release pro-inflammatory cytokines
the capsule formed by anthrax has a ____ composition
the capsule formed by anthrax has a polypeptide (glutamic acid) composition
cutaneous anthrax has a ___ mortality rate
GI anthrax has a ____ mortality rate
inhalational anthrax has a ___ mortality rate
cutaneous anthrax has a 20% mortality rate
GI anthrax has a 50% mortality rate
inhalational anthrax has a 100% mortality rate
describe the clinical presentation of cutaneous anthrax
absence of ___ is characteristic of anthrax lesions
initially: itchy papule
papule becomes a hemorrhagic vesicle
blister forms a hard, painless, blue-black leathery scab
absence of pain is characteristic of anthrax lesions
