Microbiology Flashcards
how does the skin protect itself from microorganisms?
it produces sebum inhibiting bacterial growth
dry skin desiccates organisms
competitive bacterial flora
examples of competitive bacterial flora
staph epidermidis
corynebacterium
propionibacterium
five virulence factors
adhesin invasin impedin aggressin modulin
define adhesin
enables binding of the organism to the host tissue
define invasin
enables organism to invade host cell/tissue
define impedin
enables organism to avoid host defence mechanisms
define aggressin
causes damage to the host directly
define modulin
causes damage to the host indirectly
do some people carry staph aureus on their skin?
yes
virulence factors of staph aureus
fibrinogen binding protein leucocidin (exotoxin that kills leucocytes) enterotoxin (food poisoning) TSST-1 coagulase positive (clots plasma) PVL
what is TSST-1
superantigen that produces toxins
what does TSST-1 cause?
vomiting
fever
scalded skin syndrome
toxic shock syndrome
how does TSST-1 cause damage
massive release of cytokines
describe PVL (Panton-Valentine-Leukocidin)
this is a toxin produced by a certain strain of staph aureus that kills leucocytes
what does PVL cause
furunculosis
necrotising pneumonia
necrotising fasciitis
antibiotic of choice for staph aureus
flucloxacillin
when is flucloxacillin not the antibiotic of choice for staph aureus
MRSA
what group is strep pyogenes
group A strep
what type of haemolysis is strep pyogenes
beta haemolysis
what system is used to classify the bacterial cell wall in different types of strep?
Lancefield ssytem
skin infections caused by strep pyogenes?
impetigo
cellulitis (erysipelas)
necrotising fasciitis
what does impetigo present with
honey coloured crust
define cellulitis
deeper infection of the dermis not associated with necrosis
define necrotising fasciitis
destroys connective tissue with streptomycin (SLS)
virulence factors of strep pyogenes
- superantigen
- haemolysins SLO and SLS
- M protein
two types of fungal infections in the skin
dermatophyte (ringworm)
candida
how does dermatophyte cause infection?
fungus enters soggy skin and affects keratinised tissues
causes of dermatophyte (ringworm)
trichophyton rubrum, mentagraphytes and microsporum canis
diagnosis of dermatophytosis
clinical appearance
woods light
skin scraping
hair/nail clippings
management of dermatophytosis
clotrimazole
topical nail paint (amorolfine)
management for scalp dermatophytosis
terbinafine
itraconzole
what areas does candida infect?
warm, moist areas
diagnosis of candida
swab for culture
management of candida
clotrimazole
fluconazole
two parasitic skin infections
scabies
lice
chronic form of scabies
Norwegian scabies
incubation period of scabies
6 weeks
presentation of scabies
itchy all over body rash that is worse at night
management of scabies
marathon lotion
benzyl benzoate
presentation of lice
intense itch
management of lice
malathion
infection control- singe room if…
single room isolation if strep A, MRSA or scabies
