Bacterial virulence Flashcards
Define virulence
The capacity of a microbe to cause damage to the host
Are virulence factors required for survival?
No but required to act against the host
Why can’t every S. aureus cause disease?
Because some don’t have virulence factors
Name some virulence factors and their purpose
Adhesin - enables binding of the organism to host tissue
Invasin - enables the organism to invade a host cell
Impedin - enables the organism to avoid host defence mechanisms
Aggresin - causes damage to host directly
Modulin - causes damage to host indirectly
What percentage of ppl does S. epidermidis colonise?
100%
What percentage of ppl does S. aureus colonise?
20-60%
Where are common sites of S. aureus on the body?
Anterior nares & perineum
Diagnostic criteria for toxic shock syndrome
Fever
Difuse macular rash & desquamation
Hypotension (<90mm Hg in adults)
At least 3 organ systems involved
What is the common presentation of S. pyogenes?
Streptococcal sore throat
Skin infections associated w/ S. pyogenes
Impetigo
Cellulitis (erysipelas)
Necrotising fasciitis
Virulence factors of S. pyogenes
Capsule
Haemolysins
Superantigen
Toxins
What is the Lancefield system?
Serotping of cell wall carbohydrate
Name some molecules associated w/ adhesion
Lipoteichoic acid (LTA)
Fibronectin
M protein
Hyaluronic acid
Which layer of the epidermis does impetigo infect?
Stratum corneum
Classic sign of impetigo
Golden crusts
