Gastroenteritis

Question 1

E. coli gram stain

Answer 1

• gram negative rods

- facultative anaerobes

Question 2

ETEC pathenogenesis

Answer 2

1. colonisation factor antigen (cfa) enables fimbrial adhesion
2. heat-liable (LT) toxin - AB5 cytotonic, permanent
3. heat-stable (ST) toxin - peptide, non-permanent

Question 3

EPEC pathenogenesis

Answer 3

1. bundle forming pili (bfp) enables fimbrial adhesion
2. T3SS transfers tir into cell
3. tir binds intimin
4. intimin mediates intimate adherence and A/E lesions

Question 4

EHEC pathenogenesis

Answer 4

1. stx 1 & stx 2 toxins - AB5 cytotoxic

2. toxins bind to gb3 receptor and stop protein production to kill cell

Question 5

ETEC incubation period

Answer 5

1-3 days

Question 6

EHEC incubation period

Answer 6

3-5 days

Question 7

Vibrio cholerae gram stain

Answer 7

• gram negative curved rods
• facultative anaerobes
• need 1% salt on media

Question 8

Vibrio cholerae pathenogenesis

Answer 8

1. toxin co-regulated pilus (tcp) enables fimbrial adhesion

2. AB5 cholera toxin causes intestinal hypersecretion

Question 9

Vibrio cholerae incubation period

Answer 9

1-3 days

Question 10

Vibrio parahaemolyticus pathenogenesis and incubation period

Answer 10

• invade epithelium causing bloody stools

- 6-96 hour incubation period

Question 11

Shigella gram stain

Answer 11

• gram negative rods
• facultative anaerobe
• lactose non-fermenting

Question 12

Shigella pathenogenesis

Answer 12

1. invasion plasmid antigens (ipa) via T3SS causes inflammatory immune response
2. leaky gut due to inflammation
3. icsa protein polymerises actin in bacteria
4. Stx 1 produced to kill cells

Question 13

Shigella incubation period

Answer 13

1-3 days

Question 14

ETEC sources

Answer 14

traveller’s diarrhoea - contaminated water & fruit/veg

Question 15

EPEC sources

Answer 15

contaminated water & food

Question 16

EHEC sources

Answer 16

undercooked mincemeat (hamburgers)

Question 17

Vibrio cholerae sources

Answer 17

• contaminated water & food
• coastal water & human intestinal flora
• asymptomatic human carriers (excretors)

Question 18

Vibrio parahaemolyticus sources

Answer 18

contaminated & raw shellfish

Question 19

Shigella sources

Answer 19

contaminated water & fruit/veg

Question 20

Salmonella gram stain

Answer 20

• gram negative rods

- lactose non-fermenting

Question 21

Salmonella incubation period

Answer 21

8-48 hours

Question 22

Salmonella pathenogensis

Answer 22

1. salmonella invasion proteins (sip) encoded by salmonella pathogenicity island (SPI 1)
2. SPI 2 encodes T3SS & salmonella survival antigens (ssa)
3. ssa transported to mesenteric lymph nodes via macrophages

Question 23

Salmonella sources

Answer 23

undercooked chicken and eggs

Question 24

Yersinia enterocolitica gram stain

Answer 24

• gram negative rod
• facultative anaerobe
• lactose non-fermenting

Question 25

Yersinia enterocolitica incubation period

Answer 25

4-7 days

Question 26

Yersinia enterocolitica pathenogenesis

Answer 26

1. invasin assist adhesion 2. RGD-tripeptide binds to beta 1 integrins 3. yersinia outer protein M (yopM) - regulates cell cycle 4. yopP - inhibits host cell immune response

Question 27

Yersinia enterocolitica sources

Answer 27

food borne, even when refrigerated, mostly pork

Question 28

Campylobacter gram stain

Answer 28

- gram negative curved rods | - microaerophilic

Question 29

Campylobacter incubation period

Answer 29

2-10 days

Question 30

Campylobacter pathenogenesis

Answer 30

invasion of mucosal surfaces

Question 31

Campylobacter sources

Answer 31

contaminated poultry, pets (animal reservoir)

Question 32

Staph. aureus gram stain

Answer 32

gram positive cocci

Question 33

Staph. aureus incubation period

Answer 33

1-8 hours

Question 34

Staph. aureus pathenogenesis

Answer 34

heat stable enterotoxin activates vomit centre

Question 35

Staph. aureus sources

Answer 35

food high in salt or sugar (preserved meats and cakes), found in normal skin & nose flora

Question 36

Bacillus cereus gram stain

Answer 36

gram positive rod

Question 37

Bacillus cereus incubation period

Answer 37

1-15 hours

Question 38

Bacillus cereus pathenogenesis

Answer 38

- emetic type: ST enterotoxin | - diarrhoeal type: LT enterotoxin

Question 39

Bacillus cereus sources

Answer 39

spores in rice & cereals, germinate at room temperature, do not die in flash frying

Question 40

Clostridium perfringens gram stain

Answer 40

- gram positive rod | - anaerobic

Question 41

Clostridium perfringens incubation period

Answer 41

6-24 hours

Question 42

Clostridium perfringens pathenogenesis

Answer 42

LT enterotoxin

Question 43

Clostridium perfringens sources

Answer 43

spores in soil, dust, and animals | germinate in rewarmed meat (animal reservoir)

Question 44

Rotavirus structure

Answer 44

non-enveloped, dsRNA

Question 45

Rotavirus incubation period & pathenogenesis

Answer 45

- 2 days | - enterotoxin and lysis of vili

Question 46

Norovirus structure

Answer 46

non-enveloped, positive sense ssRNA

Question 47

Norovirus incubation period & pathogenesis

Answer 47

- 1-2 days | - blunting of vili

Question 48

Adenovirus structure

Answer 48

non-enveloped dsDNA

Question 49

Entamoeba Histolytica pathogenesis

Answer 49

1. amebapores lyse host cell 2. lectin binds to host sugars for contact dependent killing 3. cystein protease breaksdown IgA & IgG 4. cleaving of complement proteins

Question 50

Giardia Lamblia pathenogenesis

Answer 50

malabsorption - attachment to gut via ventral sucking disc

Question 51

Cryptosporidium pathenogenesis

Answer 51

1. adherance via lectins and glycoproteins | 2. proteases

Question 52

Clostridium difficile incubation period & pathenogenesis

Answer 52

- days or weeks after antibiotic therapy (due to dysbiosis) - adheres to mucosa & produces cytotoxic toxins - causes pseudomembranous colitis