Microbiology Flashcards
Define ‘virulence’
The ability of an organism to cause disease within a host
Name 5 virulence factors
Adhesin Impedin Invasin Aggressin Modulin
What are adhesins?
Bacterial cell surface components that help the organism stick/adhere to host tissue
What are invasins?
Enable organisms to invade host tissue
What are impedins?
Help the organism avoid the defence/immune response in host tissue
What are aggressins?
Cause direct damage to host tissue + immune cells, affecting the host’s ability to cope with disease in the future
What are modulins?
Cause indirect damage to the host by turning the immune system in on itself (host’s immune system causes damage to host tissue)
The nasal strain of Staph. aureus can protect the mucosa. True/False?
True
Staph. epidermidis can occupy up to 100% of our skin. True/False?
True
Where is the most common entry of Staph. aureus into the body?
Nasal entry
Name the 3 particularly important virulence factors of Staph. aureus disease
Fibrinogen-binding protein (adhesin)
Leukocidin (kills leukocytes)
TSST-1 (toxin)
Every strain of Staph. aureus carries every virulence factor. True/False?
False
Which 2 severe skin diseases is leukocidin associated with?
Necrotising fasciitis
Recurrent furunculosis
Leukocidin is more virulent in hospital-acquired MRSA than community-acquired. True/False?
False
Give an example of a superantigen released by MRSA
TSST-1 (toxic shock)
How exactly do superantigens avoid specific T-cell activation?
Bind to MHC II complex on the outside, i.e. not the conventional binding groove
Name 3 skin infections caused by Strep. pyogenes
Impetigo
Cellulitis
Necrotising fasciitis
How does the Lancefield system classify different subtypes of Step. pyogenes?
M-protein
M1 and M3 are predominant; M3 and M18 cause severe, invasive disease
Which 2 virulence factors are particularly important as adhesins for Strep. pyogenes disease?
Hyaluronic acid (sticky capsule) CD44 +ve keratinocytes
The bigger the capsule, the less virulent an organism is. True/False?
False