Food poisoning Flashcards
What number and above on the bristol stool chart signifies diarrhoea?
Type 5
What is food poisoning?
Illness caused by eating food contaminated with micro-organisms, toxins, poisons etc
What sorts of pathogens can cause food poisoning?
Bacteria, viruses and parasites
Why might there be blood in the stool in food poisoning?
If the bacteria/pathogen has invaded the bowel wall
What GI symptoms are usually present with food poisoning?
Abdominal pain, vomiting, diarrhoea
Name a protozoa and a virus which are transmitted via food but do not cause diarrhoea
Hep A and toxoplasma
Which bacteria is the commonest cause of food poisoning?
Campylobacter
Which bacteria causes outbreaks?
Salmonella
Name a bacteria which is rare but causes significant morbidity and outbreaks
E. coli 0157
Where do most cases of food poisoning occur?
At home
What are relevant aspects of a patient’s history?
Diarrhoea- is there blood? History- travel, functions, contacts Suspect food Anyone else suffering? Time from ingestion of suspect food Age of patient- children have a different risk for different pathogens than adults Underlying medical problems
Which pathogens have a short incubation (time from ingestion to onset of symptoms) period of 1-6 hours?
Why is this time short?
What symptoms are there?
Staph aureus
Bacillus cereus
There is a preformed toxin which is rapidly absorbed. This acts on the vomiting centre in the brain.
There is vomiting and severe abdominal pain
Which pathogens have a medium intubation period of 12-48 hours?
What symptoms do they cause?
Salmonella
CI perfringens
There is diarrhoea which is often bloody
Which pathogens have a long intubation period of 2-14 days?
What symptoms do they cause?
Campylobacter
E.coli 0157
Diarrhoea which is often bloody
Where does bacillus cereus live?
Cereus = cereal
it lives in rice and cereal crops
used to be called chinese restaurant syndrome, as they would leave rice out overnight at room temp and fry it the next day, which did not remove the toxins.
What is the incubation period of campylobacter?
16-48 hours
What food is campylobacter found in?
Poultry and raw milk
Is campylobacter invasive?
What are the main symptoms?
Yes it is invasive.
The main symptoms are pain, blood in the stool (30%) and fever.
How should a patient with campylobacter infection be managed?
Rule of thumb is don’t use antibiotics unless you have to, i.e. if the patient has comorbid factors.
If antibiotics are used: ciprofloxacin/erythromycin
Any person with diarrhoea should be in a single room but not so vital for campylobacter because there is less chance of person to person spread.
What is the incubation period for salmonella enteritidis?
12-48 hours
What foods are salmonella enteritidis found in?
Poultry, meat and raw egg
How does salmonella enteritidis cause symptoms?
What symptoms does it cause?
By releasing toxins and invading the gut wall
It causes diarrhoea and vomiting, blood and fever
How should salmonella enteriditis be managed?
If antibiotics are required (i.e. if the patient has comorbid factors), ciprofloxacin should be used.
How is salmonella enteriditis prevented?
Food hygeine
Vaccination of hens
Animal hygeine
What type of animals that may be kept as pets can carry another type of salmonella?
Reptiles
How is salmonella typed?
- By serogrouping by different antigens on the body (e.g. the O antigen).
This is done by slide agglutination: the antigen agglutinates with the corresponding antibody - Serotyping- the serogroups are further divided by looking at the antigens on the tail of the bacterium.
E.g. salmonella enteriditis: eggs, poultry
sal. typhimurium- cooked ham
What are the commonest groups of salmonella in Tayside, in the O antigen group?
B, C and D
When should E.coli 0157 be suspected?
With bloody diarrhoea or blood per rectum
How is E.coli 0157 contracted?
Beef, raw water/milk
Person to person contact- both direct and indirect
Animal contact
Does E coli 0157 have outbreak potential?
Yes
Which toxin does E.coli 0157 produce that causes symptoms?
Verotoxin (VTEC)
What is the incubation period of E.coli 0157?
1-14 days
What are the symptoms caused by E.coli 0157?
Bloody diarrhoea
Haemorrhagic colitis
Haemolytic Uraemic Syndrome
Why should stool samples be sent as soon as possible when E.coli 0157 is suspected?
Excretion of the pathogen declines
How does haemolytic uraemic syndrome present?
Abdominal pain Fever Pallor petechiae (small red or purple dot on skin caused by haemorrhage) oliguria- low output of urine Bloody diarrhoea in 90% of cases
What ages are affected most by HUS?
Under 16 years old
Describe the blood components in HUS
High white cells Low haemaglobin Low platelets High red cell fragments LDH > 1.5 x normal May develop after diarrhoea has stopped
Can verotoxin be produced by other E coli strains as well as E.coli 0157?
Yes- there was an outbreak of 0104
What does verotoxin do?
What is its effect?
It binds to receptors found on renal cells, RBCs and others. Inhibit protein synthesis Cell swelling Intravascular coagulation Platelet aggregation Mechanical damage RBC
Causes cell death
Gives rise to HUS
What investigations are done when HUS is suspected?
Stool culture samples of all patients with bloody faeces U & E FBC LFT clotting urine lactate dehyrdrogenase
What complications can patients with HUC develop?
Acute renal failure
Thrombocytopaenia (decrease in platelets)
Haemolytic anaemia
What should patients with suspected HUC/HUC not be given?
Antibiotics- may precipitate HUC
Anti-motility agents
NSAIDs
How is E.coli diagnosed microbiologically?
Selective culture for E.coli
Sorbitol non fermenter
E coli isolated
Check if it has 0157 antigen
If there is bloody stool but negative culture:
Send for more sensitive tests
Verotoxin gene may be detected
It is typed to trace the source
When should E coli be suspected ?
Infectious bloody diarrhoea Acute onset non-bloody diarrhoea with no other explanation and likely exposure to 0157: Contact with farm animals Private drinking water Burgers Unpasteurised dairy product Contact with confirmed/susepcted case
When must be health protection unit be notified?
What do they do?
Confirmed cases of HUS or 0157
There is contact tracing and investigation
Environmental Health inspect food premises
