Lecture 6.1: Bacterial Virulence Flashcards
do bacteria always act as pathogens deliberately?
no, it can be inadvertent
infection
successful invasion of an animal/plant by a pathogen
disease
condition of unrest / discomfort
injury to host that . impairs function
virulence factors
traits evolved to promote disease
what are some examples of virulence factors?
flagella, pili, capsule
E. coli is responsible for what types of infections?
hamburger disease, UTI, diarrheal disease such as Montosmo’s revenge
how can E. coli be part of the normal flora and be so dangerous?
some have evolved to be virulent by genetic transfer
pathogenesis
creation of pathology diseased state
a major strategy of intracellular pathogens is to alter __
alter host signalling in a subtle, but significant way to promote bacterial survival
“virulence factors” was coined by
Stanley Falkow
Falkow stated that there must be a ___ that causes a bacteria to be pathogenic and that if ___, its virulence would be lost/reduced and if returned ___
gene; removed, virulence would be restored
are amino acid biosynthesis genes virulence factors?
no, unless it must be made while in host
give 3 traditional virulence factors
extracellular enzymes, exotoxins, endotoxins
function of extracellular enzymes
function outside the cell to damage host cell/tissue and can promote colonization/spreading
function of exotoxins
subversive functions on host that are very deliberate and specific
what are exotoxins?
proteins that are secreted
what are endotoxins?
bacterial products that typically have functions for bacterial survival, but can still result in diseased state for the host
examples of endotoxins
LTA and LPS
endotoxins can cause:
inflammation, haemorrhaging and damage to host
effects of endotoxins are more acute with greater number (T/F)
true
extracellualr enzymes are bacterial secreted ___ and ___
lipases and proteases
extracellular enzymes target___ and alter ___ and cause__-
surface lipids and proteins; cellular receptors; cell and tissue damage
exotoxins are usually ___ proteins that have ___ activity on host cells
soluble; cytotoxic
can exotoxins have activity even without infection or colonization?
yes
the A subunit is a ___ composed of ___
heterodimer; A1 and A2
what is the function of the A1 subunit?
ADP ribolysing activity modifies a host protein, blocking its function
what is the function of the A2 subunit?
alpha helix that sometimes requires activation by host cell protein
the B subunit is a ___ that binds to host cell ___ and functions by targeting specific ___
homopentamer; receptor (glycoprotein); cells
many AB toxins function by ___, specifically by inhibiting ___
blocking cell activity; protein synthesis
do all bacteria require a host to survive?
no
pathogen
organism that causes disease
proteases ____ host proteins and make them inactive
cleave
virulence factors help infect, colonize, hide, and resist immune attacks by ___
subverting host cellular functions
Falkow’s concept of virulence factors mirrors ___
Koch’s postulates
give an example of an extracellular enzyme involved with damaging CF lung
Pseudomonas aeruginosa
give three examples of exotoxins
clostridium botulinium, diptheria toxin, shiga toxin
