lectures 1-4 Flashcards
what are the three types of food born disease and what do they entail?
- infection - bacterial, fungi, eukaryotic parasites, viruses
- intoxication - bacterial and fungal toxins, shellfish toxins, metals and chemicals
- allergy
what are the stages of the causative chain of food-borne infections?
agent -> source -> contamination -> suitability -> growth conditions -> consumption
what are the most common sources of food-borne contamination?
- food handler
- natural food contamination
- direct contamination
- water based contamination
what are the benefits of microbe presence in food?
- food enhancement
- food additives - food safety and stability, probiotics
what are the drawbacks of microbe presence in food?
- food spoilage - shortened shelf life & failure to meet legal requirements
- food safety - morbidity & mortality
how can lactobacillaceae be a beneficial bacteria?
- it ferments sugars to lactic acid, which is used in probiotics, yoghurt, and cheese
- it outcompetes pathogens
what pH range does lactobacillaceae grow at?
pH 4-5
what is intrinsic food preservation?
- putting things in food to reduce pathogens and help in preservation
- water activity and food acidity are used for growth inhibition
- other methods are used, including antimicrobial chemicals and biological methods (competitive microflora, bacteriocins, and enzymes
what are methods of extrinsic food preservation?
- heat treatment - destruction of cells and spores
- low temperature storage - growth inhibition
- modified atmosphere packaging - growth inhibition/destruction of cells
- radiation - destruction of bacterial cells
what is hurdle technology?
- multiple preservation factors are combined to improve food safety which allows each individual measure to be milder
- can be more effective than individual processing methods
what are the key features of salmonella bacteria shape and growth?
- the bacteria is Gram negative, motile, and rod shaped
- grows at pH 4-5
- ferments sugars to lactic acid
what are salmonella’s virulence factors?
- salmonella invasion proteins
- secreted proteins
- lipopolysaccharides
what disease does salmonella cause?
enteric salmonellosis
how does human infection by salmonella occur?
- consumption of contaminated animals, animal products, or water
what does infection by salmonella result in?
- gastroenteritis
- typhoid fever
how many lab confirmed cases are there of salmonella each year in the UK?
8,500
what are the symptoms, incubation period, morbidity period, and infection type of gastroenteritis?
- symptoms - occasional vomiting, severe diarrhoea, mild fever, muscle aches
- incubation period - 8-48hrs
- morbidity period - 3-6 days
- infection type - superficial infection of the gut
what are the symptoms, incubation period, morbidity period, and infection type of typhoid fever?
symptoms - occasional vomiting, occasional diarrhoea, severe fever, sore throat/cough
incubation period - 10-14 days
morbidity period - 2+ weeks
infection type - invasive infection of the lymph nodes, the liver, the spleen, and the gall bladder
what are the key features of campylobacter sp. shape and growth?
- structure - Gram negative, mobile, spiral shaped
- growth - microaerophilic, non-fermenting
what are the virulence factors of campylobacter sp.?
- enzymatic colonisation
- adherence and invasion factors
- flagellum
- toxin (cytolethal distending toxin)
what disease is caused by the bacteria campylobacter sp.?
campylobacteriosis
where is campylobacter sp. normally found in hosts?
normally inhabits the GI tract of animals
how many people globally do not have access to safe drinking water?
785m
how is sewage treated?
1 - the raw sewage is passed through screens to separate out the grit
2 - the water moves through a series of clarifiers
3 - the clean water is floated through an aeration tank and is then disinfected
how is water treated to be used as bottled water?
1 - ozonisation occurs to help destroy all the bacteria and viruses
2 - it goes through filters to remove coarse particles, pesticides, and salts and minerals
3 - reverse osmosis occurs to remove remaining salts and minerals
4 - mineral control adds back in some minerals
name 2 waterborne diseases caused by bacteria
- cholera
- gastroenteritis (E.coli)
name 2 viral waterborne diseases
- norovirus
- rotavirus
name 3 protozoan waterborne diseases
- cryptosporidiosis
- schistosomiasis
- malaria
what are some structural features of norovirus?
- non-enveloped
- icosahedral
- single stranded RNA
what are the host and virulence factors of norovirus?
- highly contagious
- small dose needed for infection
- sheds billions of viral particles
what are the 3 open reading frames in norovirus?
ORF 1 - encodes for replicase proteins
ORF 2 - encodes the capsid proteins
ORF 3 - encodes the minor structural proteins
what type of pathogen is cryptosporidium?
- protozoan (eukaryotic parasite)
what are the 2 human pathogens associated with cryptosporidium?
C. parvum
C. hominis
what are the risk factors of cryptosporidium?
- defecating in swimming pools
- petting zoos
what are the host factors and virulence of cryptosporidium?
- symptomatic episodes of uncontrolled diarrhoea
- immune suppression
what is the life cycle of cryptosporidium?
1 - an oocyte is ingested
2 - the pathogen excyses out of the oocyte
3 - it adheres to the gut and invades and multiplies
4 - future oocytes are released in faeces
what does HACCP stand for and what are its 7 principles?
- Hazard analysis and critical control points
7 principles:
1 - list all potential hazards
2 - determine the 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 and record keeping
what elements are considered in HACCP?
- biological
- physical
- chemical
- allergen
what is hurdle technology?
- a number of preservation factors are combined to improve food safety
- it allows individual measures to be milder, increasing the naturalness of food
what is the Maillard reaction and how does it prevent microbial contamination?
- it is the non enzymatic browning of food
- it removes nutrient sources for bacteria
describe the structure and growth conditions of Listeria sp.
- structure: Gram positive, motile, rod-shaped
- growth: facultative anaerobe
what are the virulence factors of Listeria sp. ?
- biofilm formation
- haemolysis factors
- adhesion and invasion factors
- flagella
what disease does Listeria sp. cause?
Listeriosis
what are the symptoms of listeriosis?
- can be invasive or non invasive
invasive: severe headache, stiff neck, confusion, seizures, tremors
non-invasive: fever, nausea, diarrhoea, chills
what is the structure and growth conditions of Escherichia coli ?
structure: Gram negative, rod shaped
growth: facultative anaerobe
what are the virulence factors of Escherichia coli?
- LPS
- flagella
- shiga-like toxin
what disease does E.coli cause?
gastroenteritis
what was the first suggestion about the existence of the gut microbiome?
in the early 1900s, Metchnikoff was the first scientist to suggest that it was possible to modify the gut microbiome by replacing bad bacteria with good bacteria
what are commensal bacteria?
bacteria that derive an advantage from the body but do no damage
what relationship is displayed between the GI tract and the intestinal microbiota?
symbiotic
what is disruption of the intestinal microbiota homeostasis called?
dysbiosis
what are the important phyla and genera in the microbiome (give Gram stain result and examples)
- firmicutes - Gram pos - e.g. Clostridia & Lactobacillales
- bacteroidetes - Gram neg - e.g. Bacteroides spp.
- actinobacteria - Gram pos - e.g. Bifidobacteria spp.
- proteobacteria - Gram neg - e.g. Escherichia, Shigella
- fusobacteria - Gram neg - e.g. fusobacterium spp.
what did the Human microbiome project do?
- reported the structure and function of 300 healthy adults at 18 body sites
- isolated and sequenced over 1300 strains of bacteria
what factors can influence the microbiome?
- mode of delivery (vaginal/c-section)
- mode of initial feeding (breastfed/formula)
- ageing process
- diet
- geography
- medication
- stress
how does first contact influence the microbiome?
- in utero - meconium is shown to contain microorganisms but most gut microbes are acquired post-partum
- delivery mode - in vaginal births the infant is inoculated with vaginal microbiota, and skin microbiota in c-sections
when does the majority of colonisation of the microbiome occur and what influences this stage?
- environmental exposure early in life is crucial
- colonisation occurs in stages with initially only aerobic organisms
- breast milk contains over 600 species of bacteria (such as Bifidobacterium)
- breast fed infants have lower concentrations of some pathogens such as Clostridia spp.
- the microbiome stabilises in adulthood
how can ageing lead to dysbiosis and what are the effects of this?
- change in diet can lead to dysbiosis
effects: - intestinal permeability
- immune dysregulation
- potential for GIT disorders
- increased risk of C.diff infections
how can exercise induced stress lead to dysbiosis?
- the gut signals that the human host is in exercise
- the autonomic nervous system is activated, and there is bidirectional communication between the ANS and the GI tract (the gut-brain axis) mainly by the vagus nerve
- this leads to an increase in cytokines
how does alcohol cause dysbiosis? how can this be prevented?
- some people will develop alcohol induced pathology
- there is a potential decrease in the abundance of bacteroidetes and firmicutes, and an increase in proteobacteria and actinobacteria
- probiotic supplements can prevent this
