GIT Pathogens - Bacteria - Invasive

Question 1

Types of invasive pathogens
1)
2)
3)
4)
5)

Answer 1

1) Shigella
2) Salmonella
3) Yersinia enterolytica
4) Campylobacter
5) Vibrio parahaemolyticus

Question 2

Major serotypes of Shigella
1)
2)
3)
4)

Answer 2

1) Shigella flexneri
2) Shigella dysentariae
3) Shigella boydii
4) Shigella sonnei

Question 3

Shigella infective dose

Answer 3

10^2 - 10^3 bacteria

Question 4

Shigella transmission

Answer 4

Human to human. No animal vectors.

Question 5

Shigella virulence plasmid contents
1)
2)
3)

Answer 5

1) Type III secretion system.
2) Invasion plasmid antigens (ipas).
3) IcsA - Recruits host actin for motility.

Question 6

Shigella virulence plasmid size

Answer 6

240kb

Question 7

Shigella host cell, and place of entry

Answer 7

Enterocytes, basal side

Question 8

Shigella pathogenesis
1)
2)
3)
4)
5)
6)

Answer 8

1) Shigella invades, enters through M cell
2) Enters lamina propria, phagocytosed by macrophage.
3) Induces macrophage apoptosis, releases IL-1, IL-8. This causes enterocytes to become more ‘leaky.’
4) Uses ipa to enter enterocytes.
5) Uses IcsA for transport between enterocytes.
6) Shigella passes between enterocytes without becoming extracellular. Invaded cells die, focal ulcers form.

Question 9

O Antigen

Answer 9

Fimbriae

Question 10

H antigen

Answer 10

Flagella

Question 11

Immune cells that contain shigella infection

Answer 11

Neutrophils

Question 12

Lab diagnosis of shigella:
1)
2)
3)

Answer 12

1) Lactose non-fermenter
2) No motility
3) O antigens (no H antigen)
4) Desoxycholate agar (DCA)

Question 13

Pathogenic species of salmonella

Answer 13

Salmonella enteritica

Question 14

Infectious dose of salmonella

Answer 14

High - salmonella are acid-labile

Question 15

Role of ipa

Answer 15

Induce membrane ruffling in host cell.

In shigella.

Question 16

Salmonella pathogenicity island I role

Answer 16

Enter host cell

Question 17

Salmonella pathogenicity island II role

Answer 17

Survive inside host cell

Question 18

Salmonella pathogenicity island I contents

Answer 18

Type III secretion system

Sip proteins - induce membrane ruffling

Question 19

Sip protein role

Answer 19

Induce membrane ruffling in salmonella

Question 20

Salmonella pathogenicity island II contents

Answer 20

Type III secretion system

Ssa protein - Inactivate elements of innate immune system.

Question 21

Ssa protein role

Answer 21

Inactivate elements of innate immune system.

Allow salmonella to survive intracellularly.

Question 22

Salmonella pathogenesis:
1)
2)
3)
4)
5)
6)

Answer 22

1) Invade m cells and enterocytes by inducing membrane ruffling.
2) Uptake mediators induce electrolyte accumulation in the lumen, inflammatory exudate.
3) Transcytose to basal membrane, are phagocytosed, carried to regional lymph nodes.
4) Multiply in regional lymph nodes. Results in reticuloendothelial hyperplasia and hypertrophy.
5) DIsease confined to GIT by neutrophils.
6) Prostaglandins released by neutrophils increase cAMP levels, increase active fluid secretion.

Question 23

Lab diagnosis of salmonella:
1)
2)
3)

Answer 23

Desoxycitrate agar (DCA).
H2S production
Lactose non-fermenting

Question 24

Yersinia enterolytica growth temperature

Answer 24

Lower than that of other enteropathogenic bacteria

Question 25

Yersinia virulence plasmid contents

Answer 25

Yersinia outer proteins (YOP)

Question 26

Yersinia outer proteins role

Answer 26

Cytotoxic

Injected into macrophages, prevent phagocytosis

Question 27

Yersinia enterolytica pathogenesis
1)
2)
3)

Answer 27

1) Invade M cells
2) Invade basal layer, kill macrophages attempting phagocytosis. Also inhibit TNF release
3) Local systematic dissemination

Question 28

Yersinia enterolytica lab diagnosis:
1)
2)
3)
4)

Answer 28

1) CIN agar, ‘bullseye’ colonies
2) Lactose non-fermenting
3) Urease positive
4) Oxidase negative

Question 29

Foods associated with yersinia

Answer 29

Unpasteurised milk, meat

Question 30

Campylobacter infective dose

Answer 30

High. Acid-labile

Question 31

Campylobacter incubation period

Answer 31

2-4 days

Question 32

Campylobacter transmission

Answer 32

Contaminated milk, meat. Coassociation with amoebae living in water.
Non-pathogenic in chickens.

Question 33

Campylobacter pathogenesis

Answer 33

Not well understood

Might release a cytolytic toxin

Question 34

Campylobacter lab diagnosis

Answer 34

CAMP medium
Incubated at 42 degrees C
Microaerophilic conditions

Question 35

Microaerophilic conditions

Answer 35

5% oxygen
10% carbon dioxide
85% dinitrogen

Question 36

Salmonella incubation period

Answer 36

8-72 hours.