Foodborne diseases Flashcards
What is the WHO definition of a zoonotic disease?
Diseases and infections that are naturally transmitted between animals and humans
What are food borne diseases?
acute illnesses associated with arecent consumption of food
How many million deaths do you get per year from diarroheal diseases?
2.5
What is a foodborne toxin?
The result of a toxin produced by bacteria
What characterises a foodborne infection?
caused by the entrance of pathogenic microorganisms
they tend to have long incubation periods and are characterised by fever
What are the main attributes of salmonella?
- Gram negative
- In the gut
- bongori= cold-blooded animals
- enterica= major significance species, divided into 2500 specdies
What is the msot common salmonella infection in humans
S.Enteritidis
has a fatality rate of 0.12%
What kills the salmonellae
temperatures attained in commercial pasterurisation
they can remain alive in moist earth for one year and in dry earth
What are the attributes of campylobacter?
- Gram negative, spiral
- 2 species
- Microaerophilic, slightly thermophillic (41-42°C)
What food does campylobacter have a strong association with?
Poultry, water, milk
* It rarely grows on food and has a low infectious dose
What are the symptoms of campylobacter
watery/ bloody diarrhoea, abdominal pain, nausea
What kind of environments do listeria like?
Cold conditions, e.g the fridge
What are some of the symptoms of listeria?
- mild flu-like symptoms
- diarrhoea toa bortion/ life-threatening infections
What is E.Coli mostly linked to?
Poorly cooked beef or cross-contamination from raw infected meat
What is a major cause of death in HIV patients in sub-saharan africa?
Salmonella
What is a food-borne infection?
Where disease is caused by an infection (e.g salmonella/ campylobacter)
What are four types of foodborne infection?
- Bacterial foodborne e.g salmonelliosis, typhoid fever, cholera
- Viral foodborne- hepatitis A, norwalk fever
- Mycotic foodborne- candida spp
- Parasitic foodborne, including protozoa
What are the symptoms of salmonella spp.?
- Acute onset of fever
- diarrhoea
- abdominal pain
- nausea
- vomiting
- prolonged symptoms may lead to dehydration
What do salmonella grow well on?
They grow well on food
What does salmonella infect?
food item, major issue in europe
- S. Enteritidis (& S. Pullorum) can infect
developing eggs in ovaries and oviduct -
transovarian transmission - Other serovars may contaminate egg from
faeces
What are the two most common campylobacter species?
- Campylobacter jejuni
- Campylobacter coli
What is the reservoir for campylobacter?
Intestinal tract of wild/ undomesticated mammals
What are the symptoms of campylobacter?
Watery or sometimes bloody
diarrhoea, abdominal pain, fever, headache and
nausea
What is the public health significance of Campylobacter?
- It results in painful diarrhoea
- incredibly invasive disease especially in the over 65’s
- can cause neuropathological complications e.g guillan- Barre syndrome
- common cause of bacterial enteritis
What is the shape of the listeria pathogen?
Gram-positive and rod- shaped
What are almost all human cases of listeriosis caused by?
listeria monocytogenes
What temperatures does listeria grow at?
Can grow well at low temperatures
(psychrotrophic) - so particular risk
What is the reservoir for listeria monocytogenes?
Plant matter and soil
What is listeria associated with?
Cooked meats, pate, soft cheese,
How do listeria symptoms vary?
mild flu-like symptoms and
diarrhoea to abortion and life-threatening infections
characterised by septicaemia and meningoencephalitis
* Severe illness in developing fetuses, newborn infants, the
elderly and immunocompromised persons
What is the listeria fatality rate in europe?
12.7%
What are the majority of E.coli cases linked to?
poorly cooked ground/ miced beef
or cross contamination from cooked meats/ raw infected meats
How can E.coli be beneficial in the gut flora?
It can synthesise vitamin K
* E.Coli and related species form the normal gut flora
Where is E.Coli almost always found?
In the faeces, if its found in water it usually means faecal contamination
What are the groups that E.Coli strains are classified in?
- Enteropathogenic E. coli (EPEC)
- Enterotoxigenic E. coli (ETEC)
- Enteroinvasive E. coli (EIEC)
- Enterohemorrhagic E. coli (EHEC)
- Enteroaggregative E.coli (EAEC)
What is enteroinvasive E.Coli categorised by?
EIEC strains cause illness that is characterized by watery diarrhoea
in most patients.
* In addition, there is fever, nausea, and abdominal cramps.
* Bloody diarrhoea may occur in fewer than 10 % of patients.
* Illness is usually self-limiting, lasting for 2 to 3 days.
* A relatively high dose (108 cells) is necessary to produce disease
* The median incubation period is 18 hours (range 2-48h)
What is enterhoaemorrhagic E.Coli categorised by?
It is heat sensitive, but resistant to
freezing
It causes hemorrhagic colitis in humans that is
characterized by bloody diarrhoea, abdominal
pain which may be severe and vomiting.
Incubation period: 3-4 days
Few patients develop fever. Illness lasts for 4 to 8 days,
although it may extend to 13 days for severe cases
Deaths occur in patients who develop hemolytic
uremic syndrome (HUS)
What kind of bacteria are yersinia and shigella?
- Both Enterobacteriacae - similar to Salmonella & E .coli
What are the four species of shigella?
flexneri, boydii, sonnei,
dysentriae) all causing human dysentery
How is shigella usually transmitted?
Shigella can be transmitted by foodborne or person-toperson routes
What produces shiga toxins?
Some species of yersinia and shigella
What are the five types of bacterial intoxication?
- Bacterial intoxications
- Fungal intoxications
- Chemical intoxication
- Plant toxicants
- Poisonous animals
What bacterial food pathogens cause intoxication?
- staph aureus
- bacillus cereus
- clostridium
- perfringens
*
How would you categorise staph aureus?
Staphylococcus aureus is a facultative anaerobe, non-spore
forming gram positive coccus
* This type of food borne intoxication is caused by consumption of
food contaminated with staphylococcal enterotoxins produced
by certain strains of Staphylococcus aureus while growing in
food.
* The organism produces the following five serologically different
enterotoxins (A, B, C, D, E) that are involved in food borne
intoxication
* Individual strains of S. aureus may produce one or more of
enterotoxin types
How would you categorise the 5 staph aureus enterotoxins?
All the staphylococcal enterotoxins are heat stable (withstand
heating at 100 C for one hour) and ordinary cooking procedures,
pasteurisation and drying do not inactivate these enterotoxins
* They are insensitive to pH changes (pH stable) and resistant to
most proteolysis enzymes (trypsin, chymotrypsin, renin, and
pepsin)
* The enterotoxins are also not affected by irradiation.
* All five enterotoxins have the similar potency
Why does staph aureus grow poorly when growing with other mciroorganisms?
Its a poor competitor
What are the majority of staph aureus food poisonings due to?
due to foods in which the microbial flora is substantially reduced, such as cooked, cured or pasteurised foods.
What is the primary habitat of staph aureus in animals?
mucous membranes of the nasopharynx and skin of man and animals.
* Nose, skin, saliva, intestinal contents and feces.
What are the symptoms of staph aureus?
Incubation period is 1-6 hrs after consumption of food
contaminated with at least 1.0 µg of enterotoxin.
* Clinical signs include salvation, nausea, vomiting,
abdominal cramps, sometimes diarrhoea with
prostration.
* Duration of illness is 24-72 hrs.
* Dose of 1.0 µg or more is needed to cause disease
What is the structure of bacillus?
Bacillus cereus (and to a lesser extent B. subtilis) is a Gram
positive spore forming rod
What causes bacillus?
caused by consumption of
enterotoxins produced by some strains of B. cereus
What toxins does bacillus produce?
- Emetic toxin
- Two diarrhoeal enterotoxins:
a) hemolysin BL enterotoxin
b) non-hemolytic enterotoxin
What is the common source of bacillus?
bacillus is a common soil saprphyte
commonly isolated from meat, eggs, dairy products
pulses, spices, mashed potatoes
toxins are not destroyed by re-heating
What are the symptoms of emetic syndrome?
The syndrome is characterised by nausea, vomiting, abdominal
cramps and sometimes diarrhoea that occur 1-6 hrs after
consumption of contaminated food. The syndrome is associated
with ingestion of rice and pasta based foods.
What are the symptoms of diarrhoea syndrome?
In the diarrhoea syndrome, patients experience profuse diarrhoea
(watery stool), abdominal cramps and tenesmus (rarely vomiting)
beginning 8 to 16 hours after ingestion of contaminated food.
Fever is absent and symptoms resolve within approximately 12
hours.
What is the structure of clostridium?
is a genus of Gram positive spore
forming rods associated with a number of
diseases
