Lecture 15: Food Toxicology Flashcards
T/F: Food is produced globally, so strict quality control is difficult
true
what are the two things food contain?
nitrients (carbs, proteins, lipids, vitamins/minerals)
non-nutrient substances
The Food, Drug and Cosmetics Act (USA) presumes that food is safe
if it is free of certain contaminants, how are foods banned?
needs to be clear evidence that death or
illness can result from consuming it
T/F: Anything can be added to food if it falls into a class called
‘Generally Recognized As Safe (GRAS)’
true!!
Many different types of toxins can be in
our food, leading to: (4)
fish and shellfish poisoning
meat poisoning
mycotoxins
botulism
(symptoms are severe and acute, so easy to treat!)
Certified colour additives have the prefix ______
FD&C
T/F: Natural additives do not need certification (animal or plant base)
true
______ can be produced by aquatic phytoplankton
Toxins
Different diatoms & dinoflagellates can
produce different ______
toxins
how do humans normally get poisoned by shellfish?
humans normally get poisoned by eating
shellfish that have filtered these organisms (phytoplankton) from the water and accumulated the toxin
what are diatoms?
photosynthetic
organisms with a cell
wall made of
transparent silica
what causes red tides in water?
blooms of dinoflagellates, Karenia brevis
how are harmful algal blooms (increasing in biomass) such a big issue near cities?
nutrients being put into water, lots near big populated cities! (point and non-point sources)
__________:
Most common and severe type of shellfish poisoning
- Most severe outcomes in children
- Most often from eating clams or mussels
Caused by dinoflagellates that produce saxitoxin(s)
– Blocks Na+ channels keeping them closed (opposite from DDT/pyrethroids)
- Can lead to flaccid paralysis (instead of rigid paralysis)
Symptoms: tingling and numbness of face and limbs, vomiting and
diarrhea, mental status changes and respiratory failure – symptoms
appear 30-60 mins after ingestion
Paralytic Shellfish Poisoning
what organisms produce saxitoxins? what type of poisoning does this cause?
dinoflagellates
paralytic shellfish poisoning
__________
– From various brevotoxins made by
the dinoflagellate Karenia brevis
- most well known “red tide”
– Also blocks Na+ channels, but not as
severe outcomes as PSP
– Can also get exposed by inhaling
aerosolized sea spray!
Symptoms: Usually gastroenteritis with neurological
symptoms – symptoms appear 30-180 mins after
ingestion
Neurotoxic Shellfish Poisoning
what type of organism produces brevotoxins? what illness does this produce?
dinoflagellate
neurotoxic shellfish poisoning
__________
Caused by okadaic acids produced by some algae
(Dinophysis and Prorocentrum spp.).
- Most cases from eating mussels and scallops.
Symptoms: abdominal pain, diarrhea, vomiting within 2
hrs of ingestion. Symptoms gone in 2-3 days, no deaths
reported.
Diarrheic shellfish poisoning
(doesn’t involve sodium channels!!)
what type of organism produces okadaic acids? what illness does it cause?
algae (dinophysis and prorocentrum)
causes diarrheic shellfish poisoning
___________
Domoic acid is produced by the diatom Pseudo-nitzschia spp.
- Relatively rare form of shellfish poisoning
Symptoms: abdominal pain, diarrhea, vomiting within 24hrs
of ingestion followed by headache, cognitive impairment and
memory loss.
Binds to excitatory amino acid receptors in neurons,
causing Ca2+ influx in nerve cells.
1987 outbreak in PEI: 156 cases, 3 deaths, 12 with permanent short-term memory loss
Amnesic shellfish poisoning
(affecting sea lions along coast right now! more and more common as we’re adding more nutrients to the water on the coast)
_________ is produced by the diatom Pseudo-nitzschia spp.
causes what illness?
Domoic acid
amnesic shellfish poisoning
where was the largest recorded outbreak of domoic acid?
Along the North
American west coast
in 2015
Possibly linked to a
large-scale ocean
temperature anomaly
“the blob” (super high temp water region was traveling through ocean) and nutrient
enrichment along the
coast. Huge spike in diatom that produces domoic acid
closure of shellfish/finfish fisheries to protect human health, many marine mammals showed signs of domoic acid poisoning (sea lions are accumulating the highest levels for some reason, most poisoned)
_______: toxin-producing cyanobacteria, often found in Lake
Winnipeg
blue-green algae
when ______ is limited in the water, blue-green algae out-
compete green algae and lead to harmful algal blooms.
nitrogen
Green algae (plants) uptake N and P
Blue-green algae (bacteria) fix their own N
the blue-green algae Microcystis spp. make a class of 80
different toxins called _______ that are liver toxins!
(This is very toxic to dogs, issue at Lake Winnipeg)
microcystins
what do microcystins do?
inhibit the activity of protein
phosphatases that remove
phosphate groups from proteins
that are necessary for their
regulation. In the liver, this can
affect glucose metabolism.
_____ or maitotoxin produced by
Gambierdiscus toxicus
(a dinoflagellate that grows on and
around coral reefs)
Ciguatoxin
_______:
Biomagnifies
Humans exposed when they eat
contaminated reef fish.
Toxins are concentrated in fish liver,
intestines, roe, and heads.
Symptoms: cardiovascular,
gastrointestinal, neurologic, and
neuropsychiatric illness develops
within 3–6 hours
ciguatera
_________:
Named for the family Scomberidae (tunas, mahi mahi, bluefish, sardines,
marlin, mackerels)
* Can involve any fish containing high levels of free histidine.
* Improper storage allows bacteria to break down free histidine into
histamine.
symptoms resemble an acute allergic reaction with 10-60 mins of
ingestion. Antidote is antihistamines!
Symptoms: abdominal cramps and diarrhea, blurred vision and
flushing of the face and upper body (resembling a sunburn),
headaches. Usually resolve within 12–48 hrs.
A cluster of cases helps exclude true fish allergies.
Scombroid poisoning
________:
Pufferfish accumulate _____ in (mostly) their liver and gonads.
potent Na+ channel blocker (neurotoxin)
Symptoms: paralysis of muscles
including respiratory tract. Can lead
to death due to respiratory failure
within 20 min to 24 hrs
Tetrodotoxin
_____ can also be found in:
parrot fish
* Taiwanese guppies
* arrow poison frogs (Atelopus in Costa Rica)
* the blue-ringed octopus (Australia)
* certain Japanese mussels
* sea snails
* starfish
* a few types of Philippine crabs
* California newt (taricha torosa).
tetrodotoxin
T/F: Pufferfishes are resistant to tetrodotoxin (TTX) that they
accumulate primarily through their diet.
true!!
how are pufferfishes resistant to TTX?
Due to amino acid substitutions in their Nav 1.4 channel
(voltage-gated Na+ channel)
Benefits: deter predators, can also eat contaminated prey,
may be used to attract mates
T/F: Nitrite as an additive creates carcinogenic compounds
true!!!
Nitrite (NO₂− ) is used in curing meat and fish products.
* Antimicrobial activity, sensory attributes, reacts with
myoglobin and hemoglobin to form red
nitrosylcompounds.
* Nitrite reacts with 2º, 3º amines to form stable _________.
* High temperature (i.e. cooking) and acidic conditions
(i.e. digestion) increase the rate of _______ formation.
nitrosamines
_______ can lead to DNA adducts and increase
risk of cancer
Nitrosamines
In _____, the WHO upgraded cured meats to Group 1
carcinogens
2015
The high temperature breakdown of carbohydrates and proteins when
grilling and smoking meats can form _____ and heterocyclic aromatic
amines (HAAs). Which can also form DNA adducts
PAHs
All meat is now considered to be a
Group 2A human carcinogen.
Higher incidence of stomach and
colorectal cancers in heavy meat
eaters.
______ are toxins produced by fungi
Mycotoxins
300 known _______, 30 (10%) are well-characterized
* A single species of fungus may make several toxins.
* Several species of fungi can make the same toxin.
* Often, only particular strains of a species will make toxins.
* High infection rates on drought-stressed and insect-eaten plants.
* High fungal growth rates when food is stored at high humidity.
mycotoxins
T/F: Mycotoxins can also be passed from animals we consume to humans
true!!
T/F: Up to 25% of all food produced globally are contaminated to some degree by
mycotoxins!
true!!
_______:
Affects cereals, figs, oilseeds,
nuts, tobacco, and a long list of
other commodities
acute toxicity in humans rare.
Human acute symptoms include
abdominal pain, pulmonary
edema, and fatty liver and
necrosis of the liver
aflatoxins
______: these are modified furanocoumarins that are made
via fungal polyketide biosynthesis.
There are four ‘major’ ______: B1, B2, G1, and G2 (difference between 1 & 2, 2 is missing double bond)
They can be extremely toxic.
aflatoxins
T/F: Aflatoxin content can get really high in some crops!!
true! North America and Europe monitor aflatoxin levels in harvested crops.
Limits are set to 20 ppb for human consumption… 300 ppb for animal feed.
Bt corn has reduced levels of aflatoxin contamination, why?
they don’t get as much fungal growth!!
A GMO corn that express protein normally
made by the soil bacteria
- Including endotoxins
- This makes the corn resistant to some
insects
- Bt corn was developed to increase yields by
reducing insect damage
- Decrease in insect damage leads to less
fungal infestation, resulting in reduced
aflatoxin levels
_______: Caused by eating grains infected by
the fungus Claviceps purpurea
Grows in wet and overwintered grains:
rye, barley, wheat
The fungus makes sclerotia or “ergots”
by consuming a whole seed and
replacing it with fungal hyphae.
These float in water… so are easily
separated out because rye and
barley grains sink!
ergotism
what species produces domoic acid?
diatom, Pseudo-nitzschia
Ergotism is caused by _______
ergot alkaloids
________
- potent vasoconstrictor
- 5HT1a agonist
(hallucinogenic)
- Used to facilitate the delivery
of the placenta and stop
bleeding in childbirth
- WHO ‘essential drug’
Ergometrine
_______
* a potent vasoconstrictor
* Used medically to treat migraine
headaches
Ergotamine
what are the symptoms and outcomes of ergotism?
- Gangrene
Not enough blood flow to the extremities - Convulsions
From disruption in serotonin levels - Hallucinations
From disrupting certain neuro receptors - Spontaneous abortions
Not enough blood flow to the developing child
Not all outbreaks exhibit all these symptoms… likely differences in
the alkaloid profiles in different C. purpuria strains
what are the three types of bacterial borne food toxins?
exotoxins
endotoxins
botulism
_______
Toxins that are made and secreted by bacteria, but can
also be released by lysis of the bacteria.
- Proteins with enzymatic function.
- Partially degraded by cooking.
- Can be made by bacteria in contaminated food and
persist even after the bacteria is dead
Exotoxins
_______
Cell-associated substances that are structural lipopolysaccharide
components of the outer membrane of Gram-negative bacteria.
- Released from dead bacteria.
- Causes a hyperactive immune response “toxic shock
syndrome”: fever, blood clots, hypotension, shock, death
Endotoxins
________: Caused by the exotoxin botulinum (Botulinum
Neurotoxin A – BnNT A) produced by the bacteria
Clostridium botulinum
- Outbreak of _____ in Belgium 1895 revealed the cause as neuroparalytic toxin produced by anaerobic bacterium.
- Treatment: Injection of anti-botulinum toxin antibodies.
botulism
_______: forms spores
Ubiquitous in the environment
* Resistant to heat, light, drying and radiation
* Specific conditions for germination
* Anaerobic conditions
* Warmth (10-50oC)
* Mild alkalinity
C. botulinum
C. Botulinum spores
contaminates food, and if
canned will germinate and
make the exotoxin.
how can we visually tell if a can/container might have spores within it?
Puffy cans = bad!
Avoid even dented cans!
what are the three types of botulism?
food borne
infant
wound
______ botulism
* Botulism spores infect food in
anaerobic conditions
* Toxin is produced and released into
food
* Toxin concentration can be reduced
through cooking
food borne
______ botulism
* Infants ingest C. botulinum spores
* Spores germinate in gut and
bacterial colony is established, since infant gut bacteria is not thoroughly developed yet
* Bacteria colony releases toxins
* Can get this from certain foods
(especially honey and corn syrup)
Infant
_____ botulism
* Mostly associated with IV drug use
Wound
All three types of botulism can impair
neuron function. (frem cleaving SNARE proteins) Symptoms include:
- Blurred vision, drooping eyelids.
- Difficulty swallowing, muscle
weakness.
- Flaccid paralysis.
- Death due to respiratory failure.
how would we treat these symptoms?
Treatment: Inject anti-toxin antibodies
and put the patient on a ventilator.
what are the medical uses of botulinum toxin? (i.e. botox)
Used to treat conditions when
muscles contract when they
should not. Blocks the nerve
transmission that causes the
muscle cells to contract.
Used to treat:
* Migraine headaches
* Back pain
* Multiple sclerosis spasms
* Excessive sweating
Exotoxins in E. coli
Most E. coli strains are non-pathogenic
Can be passed from animal to animal through feces.
E. coli O157:H7 is a strain that can make _________.
O157:H7 strain asymptomatically grows in cow guts. Contaminated
hamburger meat and produce are the most common exposure routes
for humans. (hamburger disease!!)
- Poop contamination!
shiga toxin
when was there a REALLY bad outbreak of O157:H7 (hamburger disease)?
In 1993, there was a really bad
outbreak of O157:H7
poisonings in the USA.
* 732 infected (mostly kids)
* 10 died
* 178 with permanent nerve
and kidney damage
describe the shiga toxin structure and function, produced by E Coli O157:H7
alpha (a) subunit
The toxic catalytic bit. Cleaves the 28S ribosomal
RNA, destroying ribosomes and halting all protein
translation.
beta (b) subunit
* Interacts with a specific lipid cell membranes
(which cows don’t have!)
* Cells take it in by endocytosis. (similar to C. botulinum)
primarily occurs in intestinal epithelial cells, causing acute hemorrhagic
diarrhea and fever. Often resolves in 10 days.
In kids under 5, the elderly and immunocompromised people, the infection from ________ can
spread and cause Hemolytic-uremic syndrome
* Direct destruction of kidney cells from toxin
* Direct nerve damage
* Indirect destruction of red blood cells
shiga toxin
T/F: Most E. coli strains are non-pathogenic
true!!
