020 How Bacteria cause Disease Flashcards
Where is S.aureus normally found as a commensal organism?
Nose
Which pathogen is protein A mostly associated with and how does it evade the immune system?
S.aureus - It has an Fc receptor which binds with the Fc region on IgG, preventing the Fab region of IgG from binding to the organism.
What is coagulase and how may it help to evade immune system?
It allows bacteria to form biofilms that make it difficult for antibodies to penetrate.
What is the difference between a primary pathogen and an opportunistic infection?
Primary pathogens are able to breach host defences. Opportunistic pathogens require some underlying defect or alteration in host defences.
What are leukocydens and leukotoxins?
These directly damage phagocytes
What is an example of a polymicrobial infection?
Wet gangrene
Describe the pathogenesis of shiga toxin?
Shiga toxin causes bloody diarrhoea and haemolytic uraemic syndrome by destroying gut lining and endothelium.
Describe the pathogenesis of diptheria exotoxins?
Causes a halt in the elongation factor II, preventing protein synthesis and causing cell death (phage encoded). It leads to pharynx damage and axon damage etc.
Where is S.pneumoniae normally found as a commensal organism?
In the upper respiratory tract
What are super antigens with examples?
These antigens cause an exacerbated immune inflammatory response that could cause toxic shock syndrome etc. Respiratur burst increases oxygen free radicals. E.g. TSST and SE A-G.
Where is S.epidermis normally found as a commensal organism?
Epidermis skin
Describe the pathogenesis of tetanus toxins?
This blocks the ACh receptor, inhibiting neurons in the CNS and blocks the release of inhibitory transmitters. This causes paralysis of chest muscle.
What are endotoxins with examples?
Toxins on the cell membrane. In gram -ve, it is the lipid A moeity of LPS. In gram +ve, it is the lipotechoic acid.
What are exotoxins?
Toxins secreted outside by the cell
What is the difference between enteropathogenic E.coli and Enterotoxic E.coli?
Enteropathogenic E.coli is found on the brush border membrane. Enterotoxic E.coli have pili that adhere to mucosal epithelial cells and produce endotoxins.
