Human foodborne disease

Question 1

What is a foodborne infection?

Answer 1

Infection with an agent that results in (often diarrhoeal) disease
- frequently zoonotic

Question 2

What is food poisoning?

Answer 2

Exposure to toxins that results in disease - frequently caused by contamination, poor storage or poor handling

Question 3

What is food security, what does it exist?

Answer 3

Exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life

Question 4

What is the disability adjusted life year (DALY)

Answer 4

A measure of overall disease burden, expressed as the number of years lost due to ill health, disability or early death

Question 5

Which bacteria is the most common worldwide cause of human bacterial gastroenteritis?

Answer 5

Campylobacter jejuni and coli - 2 species

Question 6

Describe some features of campylobacter

Answer 6

Gram negative
Spiral rod
Thermophilic 41-42

Question 7

What are the symptoms of a campylobacter infection, who is most at risk of infection?

Answer 7

Diarrhoea, abdominal pain, fever, headache, nausea, vomiting 
illness can last 2 days to 2 weeks 
Affects children under 5 
Over 65s 
Bowel cancer patients

Question 8

What are the main campylobacter sources and how does transmission occur?

Answer 8

Chicken and other poultry

Bowel-to-mouth transmission via contaminated food or water

Question 9

Why is a broiler chicken so associated with campylobacter?

Answer 9

Core temp of 41-42 suits the thermophilic bacteria
Low oxygen tension in gut - microaerophiles
High faecal shedding
Intensive production, transport and processing

Question 10

What was the target set by the Food Standards agency for reducing campylobacter in broilers?

Answer 10

From 27% to 10% by 2015

Question 11

Where do most E.coli strands colonise?

Answer 11

The GI tract of cattle, sheep and goats without disease

Question 12

Give some features of Escherichia coli

Answer 12

• Gram negative rods
• optimum temp 37
• found in the GI tracts of man and animals
• heat sensitive

Question 13

What are the main sources of E.coli?

Answer 13

Undercooked beef, raw milk

Question 14

What are the most likely sources of food contamination for E.coli

Answer 14

Infected food handlers with poor personal hygiene or water contaminated by human sewage are likely sources of food contamination

Question 15

What are the symptoms of pathogenic E.coli infection?

Answer 15

Diarrhoea

Incubation period varies from 8 hours to 9 days depending on strain type

Question 16

What are some features of Listeria monocytogenes

Answer 16

Gram positive motile rod with flagellae
Optimum temp 37 - grows well at low temps
Heat sensitive

Question 17

What are the main sources of listeria monocytogenes?

Answer 17

Cooked meats, pate, soft cheese, pre-prepared sandwiches - processed food

Question 18

What are the main symptoms that come with an infection of Listeria monocytogenes

Answer 18

GI symptoms - diarrhoea, vomiting
Can cause spontaneous abortion or still birth in pregnant women
Flu like symptoms - fever

Question 19

How does infection with listeria monocytogenes occur?

Answer 19

Eating contaminated food

Question 20

Describe the features of Bacillus aureus

Answer 20

Large, gram +ve, rod, spore forming, aerobic
Wide temp range, optimum = 30-35
Heat resistant (Over 100C)

Question 21

What are the symptoms of a Bacillus aureus infection?

Answer 21

Diarrhoeal syndrome: 12 - 24h. Abdominal pain, diarrhoea and nausea.
Vomiting syndrome: 6 - 36h. Nausea, vomiting, sometimes followed by diarrhoea.

Question 22

How is bacillus aureus contaminated/transmitted?

Answer 22

Growth of bacteria in food with subsequent production of enterotoxin OR ingestion of large numbers of spores followed by their germination and enterotoxin production in the ileum

Question 23

What are the main food sources of bacillus aureus?

Answer 23

Cereals, dry vegetables, potatoes, milk and cream, rice, spices

Question 24

What are the features of clostridium botulinum?

Answer 24

Gram positive, spore forming
Proteolytic and non-proteolytic groups 
Wide temp ranges 
Doesn't grow in acidic pHs
Heat resistant

Question 25

Which clostridium species is a part of the normal gut flora?

Answer 25

Clostridium difficile

Question 26

What are the symptoms of a clostridium infection?

Answer 26

Relaxation of muscles, particularly in eyes (causes blurred vision) and around lungs (causes breathing difficulties)
Severe food poisoning: intense abdominal cramps and diarrhoea. The illness is usually over within 24 hours but less severe symptoms may persist in some individuals for 1 or 2 weeks.

Question 27

Which clostridium species causes food poisoning?

Answer 27

Clostridium perfringes

Question 28

What are the main food sources of clostridium?

Answer 28

Raw meat, poultry, vegetables

Poorly stored cooked meat - reheating

Question 29

How do bugs survive so well on food?

Answer 29

Attaching to the surface of foods or preparation areas, replicating and forming communities called biofilms