Food-borne bacterial infections

Question 1

What are the defences against infection in the GI tract of the mouth?

Answer 1

Flow of liquids
Saliva
Lysozyme
Normal bacterial flora

Question 2

What are the defences against infection in the GI tract of the oesophagus?

Answer 2

Flow of liquids

Peristalsis

Question 3

What are the defences against infection in the GI tract of the stomach?

Answer 3

Acid pH

Question 4

What are the defences against infection in the GI tract of the small intestine?

Answer 4

Flow of gut contents
Peristalsis
Mucus: bile
Secretory IgA
Lymphoid tissue (Peyer’s patches)
Shedding and replacement of epithelium
Normal flora

Question 5

What are the defences against infection in the GI tract of the large intestine?

Answer 5

Normal flora
Peristalsis
Shedding and replication of Mucus

Question 6

What are food-borne diseases?

Answer 6

Results from contamination of food by pathogens that can or cannot multiply in the food

Question 7

What is food poisoning?

Answer 7

Results from microorganisms having grown on the food to produce

Question 8

What are the two types of food poisoning?

Answer 8

Infection-type food poisoning

Toxin-type food poisoning

Question 9

What is toxin-type food poisoning?

Answer 9

Toxin (s) in the food (toxin causes clinical symptoms)

Question 10

What is infection-type food poisoning?

Answer 10

A sufficiently large population to produce an infective dose

Question 11

What are some examples of infection-type food poisoning?

Answer 11

Salmonella, Clostridium perfringens, E. coli- GI symptoms

Listeria monocytogenes- systemic symptoms

Question 12

What are some examples toxin-type food poisoning?

Answer 12

Staphylococcus aureus- enterotoxin
Clostridium botulinum- neurotoxin
Bacillus cereus- emetic and diarrhoeal toxins

Question 13

What are the two main food-related pathogens in the UK?

Answer 13

Campylobacter- food-borne

Salmonella- food poisoning

Question 14

What are the main food vesicles for passing disease?

Answer 14

Meat and poultry

Question 15

What are the greatest singe cause of human morbidity and mortality in the world?

Answer 15

Diarrhoeal diseases

Question 16

How many people are affected with a gastrointestinal infection in the UK each year?

Answer 16

1 in 5

Question 17

What is the cost of gastrointestinal infection?

Answer 17

£0.75 billion

Question 18

How many people with a gastrointestinal infection attend a GP?

Answer 18

1 in 6 cases

Question 19

What are the possible reasons for the increase in food-related illness?

Answer 19

Increase in large-scale catering
Fast food, convenience foods, packed meals-inadequate storage and reheating
Increase in factory farming (more potential pathogens in animals)
Changing patterns of shopping and food storage in the hormone
“Healthy eating”- non-processed, non-preserved food (not cooking fresh food, preserved foods have anti-bacterial products)
Staff, untrained in hygiene, working in catering establishments
Increase in travel

Question 20

What is the structure of salmonella

Answer 20

Motile, non-sporing Gram-negative rods

Facultative anaerobes

Question 21

How many types of serotypes are there in Salmonella?

Answer 21

> 2000

Question 22

What are serotypes?

Answer 22

Serotypes are groups within a single species of microorganisms, such as bacteria or viruses, which share distinctive surface structures.

Question 23

What is S. Typhi?

Answer 23

Human, systemic infection (typhoid fever)- no animal source- bloodstream and reticuloendothelial system infection

Question 24

Where does food poisoning salmonella come from?

Answer 24

Animal source

e.g. S. Enteritidies, S. Typhimurium- fever, diarrhoea, vomiting, abdominal pain

Question 25

What is typhoid and enteric fever?

Answer 25

Invasive disease restricted to humans

Question 26

What is typhoid and enteric fever associated with?

Answer 26

Associated with lack of public health services | Associated with contaminated food/water

Question 27

What is typhoid and enteric fever caused by?

Answer 27

Salmonella Typhi | Salmonella Paratyphi A, B, C

Question 28

What is the source of salmonella?

Answer 28

Live in food animals GI tract

Question 29

How can cross-contamination spread?

Answer 29

From raw meat and poultry to cooked food | Inadequate cooking and storage temperature

Question 30

What is the steps of pathogenesis for salmonella?

Answer 30

Toxins not clearly demonstrated Localised invasion of intestinal mucosa- facultative intracellular parasites Type III secretion systems essential for virulence Bacteria pass through M cells, taken up by macrophages, multiply and lyse macrophages Inflammatory response gives rise to disease symptoms Patients may continue to excrete the organism for weeks/months after recovery

Question 31

What are the steps of salmonella invading epithelial cells?

Answer 31

``` Cell opens up Produces a ruffle Induce membrane ruffle Goes inside the cell Goes into a vacuole Into the lamina propria of the gut Immune response produces macrophages Results in blood in diarrhoea ```

Question 32

What induces membrane ruffles?

Answer 32

Proteins

Question 33

What type of pathogen is salmonella?

Answer 33

Intracellular | Can survive and grow inside cells

Question 34

What does salmonella prevent allowing it to live in the cell?

Answer 34

Prevents the phagolysosome fusion

Question 35

What is Campylobacter?

Answer 35

C. jejuni (normal flora in chicken)- slender, motile, Gram-negative curved or spiral rods

Question 36

What are sources of getting campylobacter?

Answer 36

Common gut inhabitants of animals, poultry, domestic pets Meat infected with gut contents at slaughter Survive well on chickens processed rapidly and staying moist Cross contamination

Question 37

How does campylobacter survive in the GI tract?

Answer 37

Capsule

Question 38

At what age is person to person transmission of campylobacter more likely?

Answer 38

Children

Question 39

What is c. jejuni and c. coli most frequently identified to cause?

Answer 39

Acute infective bacterial diarrhoea

Question 40

What is zoonosis?

Answer 40

Pathogens acquired from animals via food (or direct contact)

Question 41

What is the pathogenesis of c. jejuni and c. coli?

Answer 41

Facultative intracellular parasites

Question 42

What do c. jejuni and c. coli invade?

Answer 42

The mucous membranesof the gut and produce Cytotoxin (s)- responsible for tissue Destruction and inflammatory diarrhoea

Question 43

What does c.jejuni and c.coli cause?

Answer 43

Causes blood in diarrhoea Sets up response in lamina propria Causes white cell production Caused by tissue invasion

Question 44

What are the 3 general preventative measures?

Answer 44

Prevention of contamination of food Prevention of growth of pathogen Rejection of suspected foods