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
role of SpiC in salmonella infection and what SPI coded for this
SPI-2
maintains SCV (salmonella-containing vacuole)
prevents fusion with lysosomes
aids development of Sifs (salmonella induced filaments) that extend from vaccuole and help get nutrinets for bacteria
role of SifA in salmonella and which SPI coded for this
SPI-2
mimics the host cells GEF (guanine exchange factors) and activates GTPases
affects intracellular signalling = redirects lysosomes away
compare the differences and similarities in invasion of hut between salmonella and shigella
salmonell and shigella both cause membrane ruffling by T3SS
however:
salmonella remians in vesicle wheras shifella rapidly escapes
