L12 - Salmonella Flashcards
what type of pathogen is salmonella
Facultive intracellular bacteria
= can replicate inside and outside of host cells
shape and gram of salmonella bacteria
gram negative motiles rods
what is salmonella a close relative of
E.coli
name the main resevoir of salmonella
Livestock - pigs,chicken,cattle
often asymptomatic
what is the most common source of infection for salmonella
Food contamination
= good heigeine is important
why is vacination preffered to antibiotics when treating salmonella and name 1 success of this movement (UK)
void promoting antibiotic resistance
= successdul vaccination strategies have made UK eggs salmonella-free
name the type of disease caused by S.Typhimurium
Enteric disease
= unpleasant but usaully reistricted to the gut and non-lethal
= usual cause by contaminated food
name the type of disease causes by S.Tpyhi
typhoid fever = systemic disease
severe and life threatening
= vaccines are imperfet but AMR - anti-microbial-resistance is a concern
name 3 of salmonellas Virulence factors
- Salmonella Pathogenicity Islands (SPIs)
= code for type 3 secretion system or effector or role in intracellular phase
- Toxins - LPS , A2B5
- Flagella and fimbrae
M (microfold) cells features and properties
specialised epithelial cells with ‘microfold’ surface instead of microvilli
= transports antigens and pathogens to underlying peyers patch for immune response
contain few lymphocytes due to just being for transport
= preffered site of infection
How does salmonella exploit M cells for infection
M cells are considered a ‘weak’ spot in intestine due to lack of dense microvili
FimH binds to glycoportein-2 on M-cells for initial adhesion
T3SS ‘inject proteins’ for membrane ruffling
doesa salmonella replicate within M-cells
Not really
= used as a ferry to reach the immune cells or underlying epithelial cells
name another way salmonella can reach underlying tissues WITHOUT T3SS
disrupt tight cell junctions
= pathogen passes between cells
how many pathogenicity isalnds that code for T3SS do salmonella have
2
= SPI-1 and SPI-2
what does SPI-1 code for
stuctural components of T3SS
some effector proteins
effect of SPI-1 mutants on invasion of M-cells in Gut
impaired invasion of M-cells but limited effect on actual virulence once inside
what does SPI-2 code for
effector proteins for intracellulatr trafficking and survival
= mutants have decreased chance of infection
what are the main role of the 2 SPIs in salmonella pathogenisis
SPI-1:
intestinal invasion
SPI-2:
role in intracellular phase and systemuc disease
= but both do have roles in both parts
what type of proteins are SopE and SopE2 screted by T3SS - SPI-1
GEFs
Guanine nucletide-exchange factors
= activate GTPase proteins by swapping the GDP (inactive) for GTP(active)
explain the role of SopE, SopE2 and SptP on Rac1 GTPase and membrane ruffling - salmonella
Rac1 is a Rho GTPase witha role in modelling the cytoskeleton
- injected proteins activate Rac1 causing production of lamelliopodia and filopdia
= protrusions of cytoskeleton
= ruffles/distorts membrane allowing salmonella to enter
- once inside SptP inactiavtes Rac to stabilise membrane preventing further disruption
what type of protein is SptP in salmella pathogensis
GAP
GTPase acting proteins = hydrolyse GTP –> GDP
inactivates the protein
SptP inactiavtes Rac1 preventing further disruption of membrane
role of SipB,SipC and SipD in infection and what pathogenicity isalnd do they come from
SPI-1
form the ‘translocon’ to ensure delivery of effector proteins
SipD - forms tip of T3SS
name the main SPI-1 proteins and brief role
Sope/SopE2:
GEFs acrtivate Rac1 = membrane ruffling
SptP:
inactivates Rac1 = stabilises host cell after internalisation
SipBCD:
form the translocon
name the 2 key proteins coded by SPI-2
SifA
SpiC
