Food Borne Infections And Toxins Flashcards Preview

PMVPH 4th Year > Food Borne Infections And Toxins > Flashcards

Flashcards in Food Borne Infections And Toxins Deck (47):
1

Give 2 old food borne diseases

* both spread feacal oral route*
> typhoid
- enteric fever caused by salmonella enterica Typhi, survives in macrophages, causes sepsis
- still present throughout the world but eradicated from UK
- carriers (GIT cells or gall bladder) can infect others, eradication hard
> cholera
- water borne
- vibrio cholerae

2

What is the best way to avoid food-borne enteritis ?

Cook your food properly
- but some foods eaten raw or rare
- can develop toxins on standing
- cooked food can be contaminated from raw food/feaces

3

5 primary agents of food borne disease in the UK

Campy
Salmonella
Listeria
E. Coli
Novovirus
(Severity and no cases in hospitals)

4

Other causes food borne illness LOOK

- s alerts
Bacillus cerise
C perfringens Yule a
Botulism
---

5

Why are burgers more likely to cause food poising than steak?

Ground meat contaminated throughout burger
- steaks only contaminated on the outside (inside equivalent to sterile wrt human pathogens)

6

Which pathogen accounts for majority of numbers of food poisoning

- campy 60%
- nori virus 30%
- salmonella very few
- norovirus and listeriosis very minimal

7

Which pathogens cause majority of HOSPITAL admission

- majority campy
- salmonella
- E. coli
- listeria
- norovirus (if immunocompromised/concurrent disease)

8

Which pathogens cause majority of deaths from food poisoning?

- campy 30%
- salmonella 20%
- E. coli 10%
- listeria 30%
- norovirus 10%

9

How has incidence of campy changed over time?

- was dropping
- since 2005 increasing again and now at higher level than initially

10

What is campy ? Subspecies? Diagnosis? How is it cultured? Incubation period?

- campylobacter jejuni (poultry)
- campylobacter coli (pigs)
- campylobacter upsaliensis (dogs)
> microaerophilic, 42*
> endemic in animals (birds and mammals)
- dx by culture of feacal sample
* zoonotic*
-2-5d incubation period

11

Pathogenesis of campylobacter

- colonised SI
- VD+ stomach pains
- fever (so innate immune system activated)

12

Majority of infection with campylobacter from which sources?

- most raw poultry
- raw meat
- infected pets and farm animals

13

Dx of campy?

- culture feacal sample
- blood agar with Abx selection
- 48hrs 42* microaerophilic
- curved G- rod

14

How can campylobacter be controlled?

COOKING ALWAYS KILLS CAMPY!

15

How does meat handling allow for campy growth

- not properly defrosted chicken
- frozen centre allows survival inside carcasse

16

What makes listeria monocytogenes special?

Can grow in the fridge (8-10*)

17

Sources of infection of listeria

- contaminated raw meat
- unpasteurised milk (pasteurising destroys listeria well)
- cheese made with unpasteurised milk
- foods containing raw vegetables
- esp organic vegetables in well manured soils

18

Incidence of listeriosis over time?

Roughly stable around 150 cases/year

19

How is listeria transmission?

- soil
- silage (can grow here)
- ingestion by animals -> encephalitis, bacteria email and abortion
- meat
- feaces
- udder -> dairy products
- humans

20

How is listeria virulent?

- get inside enterocytes
- produce haemolysin
- produce polymerised actin to propel into adjacent cells
- hide in cytoplasm safe from Abx and immune

21

Is listeria monitored and controlled tightly?

YES
- legislation

22

Who is commonly affected by listeria?

- immunocompromised individuals
- Young old
- pregnant women (people say don't have soft cheese - no reason for this! Don't have unpasteurised cheese)
- normal adults relatively resistant to disease

23

How can listeria be destroyed

COOKING ALWAYS KILLS LISTERIA

24

how has incidence of norovirus changed?

- increasing
- no actual cases 150-200,000 cases/year (lab confirmed cases 10x less than this)

25

What is norovirus ? Method of spread?

- winter vomintiing bug
- ss RNA virus
- person to person spread, food and food handlers, fomites
- feaces
> calicivirus
- single virus needed to infect, very resistant in the environment.

26

Dx of. Novirus

- RT qPCR
- unable to differentiate infective and non infective
- dx hard

27

How can norovirus be destroyed?

Proper disinfection and cooking

28

Incidence of E. Coli?

Stable but numbers higher than they should be!!

29

What is e. Coli

- Stec
- e. Coli 0157 (mostly, not all strains are this)
> bacteriophage transmits ability to product toxin (ST1 and ST2)

30

Does E. coli affect aniamlsb

Haemorrhagic D+ in calves but not major problem
- esp infects beef

31

Pathogenesis of E. coli STEC infection

- destruction of villi
- pedestals little spheres seen on micro villi characterstic

32

Is a high dose of E . Coli needed to cause disease? How does this compare tosalmonella?

- high dose salmonella needed
- low dose E. coli needed

33

Clinical, signs E. coli

- haemorrhagic colitis
- haemolytic ureamic syndrome -> renal failure

34

How have incidence of salmonella changed?

- decrease
- d/t testing and vaccination of poultry

35

Salmonella

S e term a typhimurium (poultry)
S enteridis (eggs)

36

Infectious dose salmonella

High ( relatively, still not much)
- animal feaces (human to human transmission poss but rare)

37

How have salmonella incidence been decreased?

Vaccination laying flocks

38

How can salmonella be destroyed?

Cooking

39

Dx salmonella

Enrichment selective media
- biochem serotyping O and H ???

40

How does s. Aureus cause food poisoning?

- 40% strains can produce heat stable enterotoxin (NOT DESTROYED BY COOKING)
- nasal secretion

41

Incubation period of s aureus? How long does it cause disease for?

12 hours
-> 12 hours V+
-> then resolves spontaneously (only toxin ingested, no bacterial invasion etc.)

42

How does bacillus cereus cause food poisoning?

- Cooking rice activates spores from bacillus cereus
- toxin produced on rice during subsequent incubation (eaten as reheated or fried rice)
- need to keep rice cold between cooking and reheating

43

How does clostridium perfringens type a cause food poisoning?

- feaces
- 5% strains produce enterotoxin
- contamination food stuffs incubated anaerobically
- released on sporulation

44

How does clostridium botulinum cause disease?

- from feaces and soil
- heated then bottled/canned (anaerobic)
- botulinum toxin present
- more common USA than UK
- can kill cattle if food left too

45

What is vibrio parahaemolyticus associated with?

- shell fish

46

Can you eat a 3 week old steak if it has been kept in the fridge?

Yes micro biologically safe!!

47

What can cause food poisoning?

Food borne infections
Bacterial toxins in food