Microbiology Flashcards
ways the skin protects itself from infection
- producing sebum prevents bacterial growth
- dry skin desiccates organisms
- competitive bacterial flora (staph epidermidis, Corynebacterium and Propionibacterium)
five virulence factors
adhesin invasin impedin aggressin modulin
define an adhesin
enables binding of the organism to the host tissue
define an invasin
enables the organism to invade host cell/tissue
define impedin
enables the organism to avoid host defence mechanisms
define aggressin
causes damage to host directly
define modulin
induces damage to host indirectly
staph aureus virulence factors
- fibrinogen binding protein
- leucocidin
- enterotoxin (food poisoning)
- TSST-1
- coagulase
- PVL
choice treatment for staph aureus
flucloxacillin
When is flucloxacillin not used for staph aureus
MRSA
describe TSST-1
superantigen that is associated with scalded skin syndrome and toxic shock syndrome (causes massive release of cytokines)
describe PVL strain
Panton-Valentine-Leukocidin is a leucocyte killing strain that is associated with furunculosis, necrotising pneumonia and fasciitis
strep pyogenes (group A) haemolysis
beta haemolysis
how is group A strep classified?
Lancefield system which serotypes for carbohydrate and M1 in the cell wall
three skin infections caused by strep A
- impetigo
- cellulitis (erysipelas)
- necrotising fasciitis
define cellulitis
deeper infection of the dermis not associated with necrosis
define necrotising fasciitis (group A)
destroys connective tissue with streptolysin (SLS)
virulence factors of strep pyogenes
superantigen
haemolysins SLO and SLS (aggressin)
M protein (adhesin)
two fungal infections of the skin
- dermatophyte (ringworm)
2. candida
how does dermatophyte cause skin infections
fungus enters soggy skin affecting keratinised tissues
causative organisms of dermatophyte
trichophyton rubrum
trichophyton mentagraphytes
microsporum canis
diagnosis of dermatophyte
clinical appearance (ringworm)
woods light
skin scraping and/or hair/nail clippings
management of dermatophyte
clotrimazole
topical nail paint (amorolfine)
scalp- terbinafine and itraconzole
where does candida infect?
warm and moist areas
diagnosis of candida
swab for culture
candida management
clotrimazole
fluconazole
two parasitic skin infections
- scabies
2. lice
scabies presentation
presents as an itchy rash (can have an incubation period of 6 weeks)
scabies management
malathion lotion and benzyl benzoate
presentation of lice
intense itch
management of lice
malathion
infection controls
isolation for strep A, MRSA and scabies
