L12 - Salmonella

Question 1

what type of pathogen is salmonella

Answer 1

Facultive intracellular bacteria

= can replicate inside and outside of host cells

Question 2

shape and gram of salmonella bacteria

Answer 2

gram negative motiles rods

Question 3

what is salmonella a close relative of

Answer 3

E.coli

Question 4

name the main resevoir of salmonella

Answer 4

Livestock - pigs,chicken,cattle

often asymptomatic

Question 5

what is the most common source of infection for salmonella

Answer 5

Food contamination

= good heigeine is important

Question 6

why is vacination preffered to antibiotics when treating salmonella and name 1 success of this movement (UK)

Answer 6

void promoting antibiotic resistance

= successdul vaccination strategies have made UK eggs salmonella-free

Question 7

name the type of disease caused by S.Typhimurium

Answer 7

Enteric disease

= unpleasant but usaully reistricted to the gut and non-lethal
= usual cause by contaminated food

Question 8

name the type of disease causes by S.Tpyhi

Answer 8

typhoid fever = systemic disease

severe and life threatening

= vaccines are imperfet but AMR - anti-microbial-resistance is a concern

Question 9

name 3 of salmonellas Virulence factors

Answer 9

1. Salmonella Pathogenicity Islands (SPIs)

= code for type 3 secretion system or effector or role in intracellular phase

2. Toxins - LPS , A2B5
3. Flagella and fimbrae

Question 10

M (microfold) cells features and properties

Answer 10

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

Question 11

How does salmonella exploit M cells for infection

Answer 11

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

Question 12

doesa salmonella replicate within M-cells

Answer 12

Not really

= used as a ferry to reach the immune cells or underlying epithelial cells

Question 13

name another way salmonella can reach underlying tissues WITHOUT T3SS

Answer 13

disrupt tight cell junctions

= pathogen passes between cells

Question 14

how many pathogenicity isalnds that code for T3SS do salmonella have

Answer 14

2

= SPI-1 and SPI-2

Question 15

what does SPI-1 code for

Answer 15

stuctural components of T3SS

some effector proteins

Question 16

effect of SPI-1 mutants on invasion of M-cells in Gut

Answer 16

impaired invasion of M-cells but limited effect on actual virulence once inside

Question 17

what does SPI-2 code for

Answer 17

effector proteins for intracellulatr trafficking and survival

= mutants have decreased chance of infection

Question 18

what are the main role of the 2 SPIs in salmonella pathogenisis

Answer 18

SPI-1:
intestinal invasion

SPI-2:
role in intracellular phase and systemuc disease

= but both do have roles in both parts

Question 19

what type of proteins are SopE and SopE2 screted by T3SS - SPI-1

Answer 19

GEFs

Guanine nucletide-exchange factors
= activate GTPase proteins by swapping the GDP (inactive) for GTP(active)

Question 20

explain the role of SopE, SopE2 and SptP on Rac1 GTPase and membrane ruffling - salmonella

Answer 20

Rac1 is a Rho GTPase witha role in modelling the cytoskeleton

1. injected proteins activate Rac1 causing production of lamelliopodia and filopdia

= protrusions of cytoskeleton
= ruffles/distorts membrane allowing salmonella to enter

2. once inside SptP inactiavtes Rac to stabilise membrane preventing further disruption

Question 21

what type of protein is SptP in salmella pathogensis

Answer 21

GAP

GTPase acting proteins = hydrolyse GTP –> GDP

inactivates the protein

SptP inactiavtes Rac1 preventing further disruption of membrane

Question 22

role of SipB,SipC and SipD in infection and what pathogenicity isalnd do they come from

Answer 22

SPI-1
form the ‘translocon’ to ensure delivery of effector proteins

SipD - forms tip of T3SS

Question 23

name the main SPI-1 proteins and brief role

Answer 23

Sope/SopE2:
GEFs acrtivate Rac1 = membrane ruffling

SptP:
inactivates Rac1 = stabilises host cell after internalisation

SipBCD:
form the translocon

Question 24

name the 2 key proteins coded by SPI-2

Answer 24

SifA

SpiC

Question 25

role of SpiC in salmonella infection and what SPI coded for this

Answer 25

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

Question 26

role of SifA in salmonella and which SPI coded for this

Answer 26

SPI-2

mimics the host cells GEF (guanine exchange factors) and activates GTPases

affects intracellular signalling = redirects lysosomes away

Question 27

compare the differences and similarities in invasion of hut between salmonella and shigella

Answer 27

salmonell and shigella both cause membrane ruffling by T3SS

however:
salmonella remians in vesicle wheras shifella rapidly escapes