Bacterial foodborne pathogens Flashcards
Which bacterial foodborne pathogens are gram negative?
Salmonella Campylobacter E.coli Shigella Yersinia Vibrio
Which bacterial foodborne pathogens are gram positive?
Listeria
Staphylococcus
Clostridium
Bacillus
What is foodborne intoxication?
Organism produces toxins that are ingested
Does foodborne intoxication have a slower or faster onset?
Rapid onset
What are the two types of food borne infection? What do these mean?
Invasive infection - bacteria ingested in food and penetrate intestinal mucosa (can cause local or systemic disease)
Toxicoinfection - bacteria ingested in food and produce toxins in the GI tract
What bacteria causes Yersioniosis? Cool fact about Yersinia?
Yersinia enterocolitica
Another species caused the black death
Yersinia is the 3d most common food disease. Is it’s bacteria gram positive or negative? What shape is it? Is it motile?
Gram negative
Rod shaped - NON spore forming
Motile at room temperature only - not body temp
Where is Yersinia enterocolitica found?
Throat, tonsils and faeces of PIGS
avoid during evisceration
How is yersioniosis transmitted?
Faecal oral route
Asymptomatic carriers
What symptoms does Yersioniosis cause?
Fever
Gastroenteritis with haemorrhage diarrhoea
Pseudo-appendicitis
Vibrio species are what type of bacteria? (O2 requirement, shape, salt requirement)
Facultative anaerobes
Straight or curved rods
Halophilic - need NaCl
What is the primary source of Vibrio infection?
Contaminated water or shellfish
Poor sanitation
What bacteria causes cholera? What is the incubation period and symptoms?
Vibrio cholerae
6 hrs
Severe pain, profuse watery diarrhoea, vomiting, dehydration, acidosis shock and death if not rehydrated
How can Vibrio bacteria be controlled?
Consume clean water
Dispose of sewage correctly
Don’t eat seafood from waters containing cholera
What are the two other species of Vibrio (except cholerae). Which is mild and which is severe?
Vibrio parahaemolyticus - mild
Vibrio vulnificus - severe
What bacteria causes invasive listeriosis infection? What is the main source of this bacteria (organisms)?
Listeria monocytogenes Animal intestines (asymptomatic carries) and humans
Is listeria motile at room or body temperature? What is it very resistant to?
Room temperature = motile
Desiccation
What foods can listeria monocytogenes be found in?
Raw milk
Soft cheese
Vegetables
Unpasteurised juice
What is the incubation period of invasive listeriosis? How does it enter the CNS?
Up to 21 days
Invades GI mucosa, enters macrophages which go through the bloodstream to the CNS
What are the symptoms of invasive listeriosis?
Septicaemia
Meningitis
Encephalitis
Abortion
What are the symptoms of non-invasive listeriosis?
Diarrhoea
Mild fever
Headache
Myalgia (muscle pain)
How long is the incubation period of non-invasive listeriosis?
Much shorter = 1-3 days
Where is staph aureus found and what is the name of the disease it causes?
Skin, hands, nares, milk, environment
Staphyloenterotoxicosis
Is staph aureus motile or non-motile? What air conditions does it prefer? What is it very resistant to?
Non-motile
Facultative anaerobe
Desiccation (enterotoxin also resistant to heat)
Which bacteria are resistant to desiccation?
Listeriosis
Staph aureus
How many toxins does staph aureus produce? Which are the most common?
8
A and B
What is the incubation period of staphyloenterotoxicosis? What are the symptoms
1-6 hrs
NO FEVER
D+, V+, abdo pain
What bacteria causes botulism and infant botulism? What foods is it associated with?
Clostridium botulinum
Honey, poorly canned foods
What environment does clostridium botulinum need to form spores? How does it cause cell death?
Anaerobic
Produces toxins which block nerves - paralysis and death
What is the difference between botulism and infant botulism?
Botulism - intoxication, affects adults
Infant botulism - toxico-infection, children <1
Why are children more susceptible to infant botulism? What ar eat symptoms?
Don’t have established gut flora
Constipation, respiratory distress
How long is the incubation period of Botulism?
1-3 days
Are botulism spores heat resistant? How can botulism be prevented?
No
Toxins sensitive to heat - heat at 80 degrees for 30 mins
What two syndromes does bacillus cereus form?
Emetic syndrome
Diarrhoeal syndrome
What type of gram is bacillus cereus? What shape is it? Is it motile? Does it have spores/toxins?
Gram positive
Rod
Motile
Spores and toxins - v resistant to heat
What foods are associated with bacillus cereus?
Rice
Pulses
What type of infection is Bacillus cereus emetic syndrome? Can the cells be killed by cooking? What are the symptoms?
Intoxication
No - vegetative cells killed but spores and toxins are not
Rapid vomiting (within minutes)
What type of infection is Diarrhoeal syndrome by bacillus cereus? How is it caused? What are the symptoms?
Toxico-infection
Spores/vegetative cells ingested and toxins produced in the GI
Short, profuse painful D+ within hrs
Clostridium perfringens produce what type of toxin? What is interesting about this?
Type A toxin
Survives in GI tract = asymptomatic carriers
What affect does cooking have on spores? Why?
Activates them
Germinate in anaerobic conditions
What is the most common source of Clostridium perfringens?
Cooked meat
TURKEY
What are the symptoms of Clostridium perfringens infection? How long does it last?
Severe abdo pain
D+++
2 days - fatal if immunocompromised
How can foodborne bacterias be prevented?
Cook thoroughly
Rapid chill
Reheat to 75/80 degrees for over 30 mins
