Food- and Water-borne Infections (1-4)

Question 1

What are the 3 types of food borne disease?

Answer 1

1. infection
   → bacterial, fungal, eukaryotic parasites, viruses
2. intoxication
   → bacterial and fungal toxins, shellfish toxins, metals, chemicals
3. allergy
   → usually to specific proteins

Question 2

What is the causative chain of infection for food borne disease?

Answer 2

agent → source → contamination → suitability → growth conditions → consumption

break one of these connections to prevent infection

Question 3

What are some sources of food contamination?

Answer 3

1. food handler associated
   → inadequate personal hygiene, faecal contamination
2. food processing
   → equipment, packaging, personnel
3. food storage
   → time and temperature
4. food product
   → e.g meat and poultry - contaminated feed, animal-animal transmission, soil contamination

Question 4

What are the pros and cons of microbes in food?

Answer 4

pros:
→ food enhancement - improve taste in e.g. cheese, meat wine
→ food additives - for safety and stability, probiotics

cons:
→ food spoilage - shortened shelf life, failure to meet legal requirements
→ food safety - morbidity (feeling unwell), mortality

Question 5

How can food be preserved intrinsically?

Answer 5

1. water activity → availability of water for growth inhibition
2. ph - food acidity → growth inhibition
3. antimicrobial chemicals
4. biological: competitive flora, bacteriocins, enzymes

Question 6

How can food be persevered extrinsically?

Answer 6

1. heat treatment → destruction of cells and spores
2. low temp storage → growth inhibition
3. modified atmosphere packaging → growth inhibition, destruction of cells
4. radiation (UV, microwave, gamma) → destruction of bacterial cells

Question 7

What is hurdle technology?

Answer 7

Using a combination of actions to prevent growth - more hurdles for microbes to overcome
→ a number of food preservation factors are combined to improve food safety
→ allows the measures to be milder, food more natural
→ can be more effective than individual processing measures

? can lead to development of ‘tougher’ more resistant bacteria

Question 8

How does salmonella affect the human body?

Answer 8

Salmonella is found in the intestinal tract of birds and other animals - human contamination occurs through consumption of contaminated animals, animal products, water
→ infection results in gastroenteritis or typhoid fever

Question 9

What is typhoid fever?

Answer 9

Bacterial infection of the lymph nodes, liver, spleen and gall bladder
symptoms → occasional vomiting/diarrhoea, severe fever, cough, occasionally fatal
→ not endemic to the UK

Question 10

How can Campylobacter infection be prevented?

Answer 10

Commonly found in poultry, read meat (GI tract of animals), untreated water
→ prevented by sufficient cooking, good hygiene, correct processing by food/water providers

Question 11

What is the difference between non invasive and invasive Listeriosis?

Answer 11

Non invasive → infects digestive system, mild, symptoms: fever, muscle pains, nausea, diarrhoea

Invasive → infects blood, CNS brain, more severe, septicaemia, symptoms: sever headache, stiff neck, confusion, seizure, tremors, high risk people for susceptible

Question 12

What is the difference between enterohemorrhagic and enterotoxigenic E. coli infection?

Answer 12

Enterohemorrhagic → infects colon, symptoms: sever stomach cramps, vomiting, diarrhoea, complications: development of Haemolytic Uremic Syndrome

Enterotoxigenic → infects gut, symptoms: diarrhoea, occasional vomiting, complications: rare, usually self limiting

same at risk population → elderly, young, newborns

Question 13

What are the common methods used to ensure food safety?

Answer 13

1. intrinsic preservation → e.g. water, pH
2. extrinsic preservation → e.g. heat treatment, packaging
3. huddle technology
4. hygiene

Question 14

What are the major food-borne pathogens?

Answer 14

E.coli
Salmonella
Listeria

Question 15

What can cause water to be unclean/unsafe?

Answer 15

Bacterial, viruses, protozoa, chemicals, mud, particulate matter, sewage

Question 16

What is being done to improve water management?

Answer 16

WHO sates: no one should die/get sick from contaminated water, no child should have to stay home from school due to lack of clean toilet and privacy, no one should suffer indignity of having to defecate in the open

WHO + unicef → want to provide equitable access to safe sanitation (manage waste) by 2030 and soap and water for hand washing in all homes by 2030

Question 17

What does it take to make our water clean?

Answer 17

Water filtration → removing particulate matter
Sewage treatment → raw sewage screened, clarified, aerated, clarified, disinfected

Question 18

How is bottled water treated?

Answer 18

Source: groundwater
Ozonisation → destroy bacteria
Sand/carbon filters
Polisher filter
Reverse osmosis
Mineral control

Question 19

What defines if water is safe?

Answer 19

Acceptable limits for clean safe drinking water
→ E.coli = 0/100 ml
→ coliforms = 0/100 ml
total viable counts
→ 37C = 10 cfu (colony forming units)/ml

Indicator organisms include (if found unfit for consumption): Campylobacter, norovirus, Cryptosporidium

Question 20

What are the main waterborne diseases?

Answer 20

Bacterial → Vibrio cholerae: Cholera, E. coli: gastroenteritis

Viral → norovirus, rotovirus

Protozoan → Cryptosporidium parvum: cryptosporidiosis, Plasmodium spp,: Malaria

Question 21

Why is norovirus deemed a ‘shape-shifter’?

Answer 21

Ability to mutate rapidly and frequently, created variation in binders and antibodies
→ high variability means no future protection if previously infected
(caspid has lots to do with virulence factors)

Question 22

Why was NASA involved in improving food safety guarantee?

Answer 22

NASA needed a food safety programme to guarantee 100% foo safety
→ feed astronauts nutritional, good quality, safe food
→ wanted to identify hazards and eliminate so made HACCP

Question 23

What is HACCP?

Answer 23

Hazard Analysis and Critical Control Points
→ monitoring critical control points, keep records of the history of food products
→ identify, evaluate and control food hazards

Question 24

What are the 7 principles of HACCP?

Answer 24

1. list all potenial hazards
2. determine CCPs (critical control points)
3. establish critical limits for each CCP
4. establish a monitoring system
5. establish corrective measures
6. establish verification procedures
7. establish documentation/record-keeping

Question 25

What is an advantage of food hurdle technology?

Answer 25

Many small hurdle used together is more managable and doesn’t compromise quality or taste

Question 26

How is hurdle technology used in jam making?

Answer 26

Hurdle 1: heat treatment + acidity
→ reduction in microbial population
Hurdle 2: addition of sugar
→ low growth
Hurdle 3: vacuum formed
→ limits exposure to oxygen, growth inhibited

Question 27

What is the Maillard reaction?

Answer 27

Occurs during cooking, browned food: amino acids and sugar react together
→ makes sugar unavailable to microbes, limiting growth

Question 28

How can shelf life of pineapple be extended?

Answer 28

1. dipping in sugar solution - osmotic drying, reduces water activity
2. dipping in potassium metabisulfite solution - inhibits enzymatic browning
3. infrared drying - reduces water activity

Question 29

Does bacteria community composition change at different body locations?

Answer 29

Yes - in a healthy human bacterial community composition changes depending on the body locations

Question 30

What discovery did Elie Metchnikoff make?

Answer 30

First scientist to suggest that is was possible to modify the gut microbiome by replacing with good bacteria
→ hypothesised that seeding the gut with healthy bacteria by drinking fermented milk products could fight off harmful bacterial and prolong life

Question 31

What is the gut microbiome?

Answer 31

Trillions of bacteria in the GI tract
→ mostly commensal bacteria (reside without harming human health)
→ associations between individuals related to whether they were breastfed, gender, education level

Question 32

What is disruption to microbiota homeostasis called?

Answer 32

Dysbiosis
→ leads to chronic inflammation

Question 33

What are some phyla and genera present in gut microbiomes?

Answer 33

Firmicutes
Bacteroidetes
Actinobacteria
Proteobacteria
Fusobacteria

Question 34

What is the Human Microbiome Project?

Answer 34

An attempt to characterise the structure and function of the microbiome
→ 300 healthy adults, 18 body sites
→ isolated and sequenced over 1,300 reference strains
→ build a stronger picture of microbiomes

Question 35

What is the microbiome influenced by?

Answer 35

→ mode of delivery
→ mode of initial feeding
→ ageing process
→ diet
→ geography
→ medication (antibiotics)
→ stress

Question 36

How does exercise induced stress affect the microbiome?

Answer 36

Bidirectional communication between ANS and GI tract, the gut-brain axis, by the vagus nerve
→ exercise stress leads to release of noradrenaline and adrenalin and glucocorticoids
→ microbiome affected by this stress and influences these reactions

Question 37

How do bacteria connect to the brain?

Answer 37

Bacteria signals with host by:
→ bacterial sub products via the bloodstream
→ cytokine release from mucosal immune cells
→ release of gut hormones like serotonin
→ afferent neural pathways, vagus nerve
→ LPS-induced intestinal permeability

Question 38

How is the GI tract affected by over exercise?

Answer 38

Over exercise increases permeability of gut microbiome → flood of signals
intestinal barrier compromised → increased temperature, reduction in blood flow, dysbiosis

Question 39

How can alcohol effect the microbiome?

Answer 39

Alcohol effects the composition of the microbiome
→ can be restored by pro-biotic supplementation

Question 40

Can diseases effect the microbiome?

Answer 40

Yes
→ e.g. inflammatory bowl disease, type 2 diabetes, necrotising enterocolitis

Question 41

What is faecal microbiota transplantation?

Answer 41

Transfer of processed stool of healthy bacteria form a donor into patients intestine
→ restores balance of bacteria in microbiome + ability to fight infection