L49

Question 1

Salmonella
GN or GP
Motile? 
Grow on MacConkey
Lactose -/+
Glucose ferment yes or no?

Answer 1

GN
Motile b/c of flagella 
Yes on MacConkey
Lactose - 
No glucose fermentation

Question 2

How are salmonella strains typed?

Answer 2

O & H antigens = serotyping

Question 3

Salmonella transmission

Answer 3

Food (undercooked chicken)
- For all types of salmonella disease this is true (w/ or w/o GI symptoms)
Cold blooded animals - turtles

Question 4

What are the 2 classifications of salmonella? Diseases caused by each.

Answer 4

Non-typhoid = inflam diarrhea
- Issue in AFRICA where causes bactermia in kids!!
Typhoid = typhoid fever, life threatening

Question 5

Treatment for salmonella food poisoning

Answer 5

NONE

Question 6

Which patients should you worry about if they get non-typhi salmonella food poisoning?

Answer 6

Immunocompromised - may progress to systemic bacteremia

Question 7

Which strains of salmonella cause typhoid fever?

Answer 7

S. typhi

S. paratyphi

Question 8

Typhoid fever clinical presentation

Answer 8

Look sick
Rose spots on stomach
Constipation - pea soup diarrhea (not prominent feature)

Question 9

How can you be a carrier of salmonella?

Answer 9

Asymptomatic if carried in gall bladder
- Remove gall bladder = no longer a carrier
Typhoid Mary

Question 10

Complications of untreated typhoid fever

Answer 10

Intestinal hemorrhage –> death

Question 11

How do you treat typhoid salmonella?

Answer 11

Indicated but unclear due to multidrug resistance

Question 12

What is the salmonella vaccine?

Answer 12

Vs. s.typhi strain

1. Oral, live attenuated
2. Polysaccharide of Vi capsule

Question 13

Where does a salmonella infection start in the body?

Answer 13

SI
Non-typhoid - stops here, causes GI symptoms
Typhoid - invades mucosa –> circulation

Question 14

How does typhoid salmonella get into the SI mucosa?

Answer 14

T3SS (SPI 1)- changes actin –> induce own update
A different T3SS (SPI 2) X PL fusion
Multiple inside protected phagosome
Escape –> inflammation

Question 15

Which type of salmonella do you see significant inflammation (vs. minimal)?

Answer 15

Non-typhoidal

Does this via surface LPS & flagella

Question 16

Which type of salmonella do you see large neutrophil response?

Answer 16

Non-typhoidal

Question 17

What virulence factors are unique to typhoid salmonella?

Answer 17

Vi capsule - decreased inflam response (why typhoid has little inflam)
- Prevents interaction of LPS w/ host PRRs
Can downregulate flaeglla

Question 18

Why is it adventageous that salmonella cause some inflammation?

Answer 18

Competitive advantage
Can secrete lipocalin to inhibit host antimicrobial peptides
BUT normal gut flora can’t!
Salmonella > other gut microbes

Question 19

Shigella
GN or GP
Shape
Motile?
Grow on MacConkey
Ferment lactose?
Ferment glucose?

Answer 19

GN
Rods
Non-motile
Grow on MacConkey
NO lactose fermentation 
YES glucose fermentation 
(Same GN flowchart path as salmonella)

Question 20

What is unique about how shigella is transmitted?

Answer 20

SMALL infectious dose

Therefore, transmitted person-person via fecal-oral

Question 21

Symptoms of shigella infection

Answer 21

1. Abdominal cramps

2. Dysentery = mucous, bloody diarrhea w/ WBCs

Question 22

What are the complications of untreated shigella?

Answer 22

Colitis –> hemorrhage
Malnutrition –> cognitive defects in kids
Rectal prolapse
Reiter’s syndrome

Question 23

Shigella pathogenesis

Answer 23

Infects M cells sampling lumen contents
Into macrophages --> kills them 
- Via T3SS
Apoptosis triggers inflam rxn (IL 8)
Invades other GI epithelial cells from BL side via vacuoles --> use host cell actin to move and infect neighboring cells

Question 24

What surface protein does shigella use to infect cells from BL side?

Answer 24

VirG

Question 25

Where are most of shigella’s virulence factors contained? What virulence factor is it lacking?

Answer 25

VF on plasmids + PI in chromosomes

Lacking Avl –> why this strain is so pathogenic vs E.Coli which still has this gene

Question 26

Treat shigella infection

Answer 26

Fluids
Antimicrobials can be helpful - but immune system will eventually clear the bug, question is how long/how severe are symptoms

Question 27

Which strain of shigella is more virulent than the others? Why?

Answer 27

S.dysenteriae
+ shiga toxin –> cleaves host rRNA
Associated with HUS complications in kids

Question 28

Why does s.dysenteriae often become epi/pandemic?

Answer 28

No baseline level of immunity for this