Human foodborne disease Flashcards
What is a foodborne infection?
Infection with an agent that results in (often diarrhoeal) disease
- frequently zoonotic
What is food poisoning?
Exposure to toxins that results in disease - frequently caused by contamination, poor storage or poor handling
What is food security, what does it exist?
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
What is the disability adjusted life year (DALY)
A measure of overall disease burden, expressed as the number of years lost due to ill health, disability or early death
Which bacteria is the most common worldwide cause of human bacterial gastroenteritis?
Campylobacter jejuni and coli - 2 species
Describe some features of campylobacter
Gram negative
Spiral rod
Thermophilic 41-42
What are the symptoms of a campylobacter infection, who is most at risk of infection?
Diarrhoea, abdominal pain, fever, headache, nausea, vomiting illness can last 2 days to 2 weeks Affects children under 5 Over 65s Bowel cancer patients
What are the main campylobacter sources and how does transmission occur?
Chicken and other poultry
Bowel-to-mouth transmission via contaminated food or water
Why is a broiler chicken so associated with campylobacter?
Core temp of 41-42 suits the thermophilic bacteria
Low oxygen tension in gut - microaerophiles
High faecal shedding
Intensive production, transport and processing
What was the target set by the Food Standards agency for reducing campylobacter in broilers?
From 27% to 10% by 2015
Where do most E.coli strands colonise?
The GI tract of cattle, sheep and goats without disease
Give some features of Escherichia coli
- Gram negative rods
- optimum temp 37
- found in the GI tracts of man and animals
- heat sensitive
What are the main sources of E.coli?
Undercooked beef, raw milk
What are the most likely sources of food contamination for E.coli
Infected food handlers with poor personal hygiene or water contaminated by human sewage are likely sources of food contamination
What are the symptoms of pathogenic E.coli infection?
Diarrhoea
Incubation period varies from 8 hours to 9 days depending on strain type
What are some features of Listeria monocytogenes
Gram positive motile rod with flagellae
Optimum temp 37 - grows well at low temps
Heat sensitive
What are the main sources of listeria monocytogenes?
Cooked meats, pate, soft cheese, pre-prepared sandwiches - processed food
What are the main symptoms that come with an infection of Listeria monocytogenes
GI symptoms - diarrhoea, vomiting
Can cause spontaneous abortion or still birth in pregnant women
Flu like symptoms - fever
How does infection with listeria monocytogenes occur?
Eating contaminated food
Describe the features of Bacillus aureus
Large, gram +ve, rod, spore forming, aerobic Wide temp range, optimum = 30-35 Heat resistant (Over 100C)
What are the symptoms of a Bacillus aureus infection?
Diarrhoeal syndrome: 12 - 24h. Abdominal pain, diarrhoea and nausea.
Vomiting syndrome: 6 - 36h. Nausea, vomiting, sometimes followed by diarrhoea.
How is bacillus aureus contaminated/transmitted?
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
What are the main food sources of bacillus aureus?
Cereals, dry vegetables, potatoes, milk and cream, rice, spices
What are the features of clostridium botulinum?
Gram positive, spore forming Proteolytic and non-proteolytic groups Wide temp ranges Doesn't grow in acidic pHs Heat resistant
Which clostridium species is a part of the normal gut flora?
Clostridium difficile
What are the symptoms of a clostridium infection?
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.
Which clostridium species causes food poisoning?
Clostridium perfringes
What are the main food sources of clostridium?
Raw meat, poultry, vegetables
Poorly stored cooked meat - reheating
How do bugs survive so well on food?
Attaching to the surface of foods or preparation areas, replicating and forming communities called biofilms
