Microbiology Flashcards
What are virulence factors?
Proteins contributing to variation in virulence between microorganism
organisms able to up or down regulate production depending on environment
Adhesins
Enable binding of organism to host
These dictate where within the body the organism can take hold
Invasin
Enables microorganism to invade host
Impedin
Enables microorganism to avoid hosts immune system
Aggresin
Cause direct damage to the host
Modulin
cause indirect damage to the host
Name two virulence factors associated with Staph.aureus
TSST-1 a superantigen binds directy to MHC II causing cytokine storm and inappropriate immune response
SSST Scalded skin syndrome a toxin which breaks down crossbridges between cells
Clinical signs of toxic shock syndrome
Fever >39, diffuse macular rash, hypotension <90mmHg,
Panton- Valentine Leukocidin- PVL toxin
Has a specific toxicity to leukocytes so removing immune response. Presence on skin isn’t an issue but very high mortality when present in the blood.
What does PVL trigger?
Necrotising Pneumonia- rapid progression acute respiratory distress with refractory hpoxaemia
Streptolysin S
a virulence factor which is a pore forming cytolising chemical toxic to organelles and platelets
What does Streptolysin S result in?
Necrotising fasciitis- penetrates into dermis and mucous membrane and destroys connective tissue
Pain is out of proportion to the inflamed rash
Debridment is only cure
Name three commensal bacteria found on the skin
Staph epidermidis
Diptheriods
Propionibacterium
Name the types of bacteria likely to cause skin infections
Staph Aureus
B haemolytic group A
Staph Aureus
Gram +ve Cocci in clumps, coagulase +ve,
Respire aerobically but can function anaerobically
What is special about staph aureus?
Produces a protein which cause clothing off the blood plasma.
Name three virulence factors linked to Staph Aureus?
SSST scalded skin syndrome toxin
PVL Panton Valentin Leukocidin toxin
Enterotoxin- food poisoning
What antibacterial is used for Staph Aureus?
Flucloxacillin
Pen allergic use Vancomycin
Staph Epidermidis
Skin commensal not commonly linked to infection
coagulase -Ve
If upon swabbing Staph epidermidis keeps appearing what is likely route of infection?
Linked to artificial implant like heart valve catheter IV lines etc
Staph Saphrophyticus
Linked to urinary tract infections in women of child bearing age
Streptococcus
gram +ve chains
B haemolytic Group A
Strep Pyogenes
Common in infected eczema and impetigo
Treatment for Strep Pyogenes?
Penicillin if no Staph aureus is found, if Staph Aureus is present treat with flucloxacillin.
