Diarrhoea Flashcards
Definition of gastroenteritis
Inflammation of the stomach/intestines often causing three or more loose stools per/day with accompanying features of vomiting and pain
What chart shows the different types of stools?
Bristol stool chart
Causes of gastroenteritis
Contamination of food stuff e.g. chicken and campylobacter
Poor storage of produce e.g. bacterial proliferation at room temperature
Travel related infections e.g. salmonella
Person to person spread e.g. norovirus (principally for viruses)
What is the commonest bacterial pathogen of infection?
Campylobacter
Differential diagnosis of gastroenteritis
IBD (history >2 weeks)
Spurious diarrhoea
Carcinoma
What is spurious diarrhoea secondary to?
Constipation
Treatment of gastroenteritis
Rehydration
- oral with salt/sugar solution
- IV saline
Antibiotics possibly (not in healthy patient with non-invasive infection)
Antibiotics are indicated in gastroenteritis for….
Immunocompromised Severe sepsis or invasive infection Valvular heart disease Chronic illness Diabetes
Incubation of campylobacter gastroenteritis
up to 7 days so dietary history may be unreliable
usually 2-3 days - a week unlikely
Do you get chronic infection with campylobacter gastroenteritis?
No - stools negative within 6 weeks
Post infective sequalae of campylobacter gastroenteritis includes;
Guillian-Barre syndrome
Reactive arthritis
What is the commonest cause of food poisoning in the UK?
Campylobacter
- C. Jejuni
- C. Coli
When does the symptoms for salmonella gastroenteritis usually occur after exposure?
Symptom onset usually <48 hours after exposure
How long does diarrhoea usually last with salmonella gastroenteritis?
< 10 days
Commonest salmonella infections in the UK
Salmonella enteriditis
Salmonella Typhimurium
What do S. typhi and S. paratyphi cause?
Enteric fever (typhoid and paratyphoid) NOT gastroenteritis
What bacteria causes food poisoning from reheated rice?
Bacillus cereus
Definition of infection in respect to food poisoning
Ingesting the pathogen that duplicates
Definition of intoxication in respect to food poisoning
Damage to the host cells from the toxins that were in the food
What history is usually present with C. Diff diarrhoea?
Previous antibiotic treatment - “the 4Cs antibiotics”
What is Clostridium Difficile (C. Diff)?
Gram positive anaerobe
Does C. Diff form spores?
Yes, heat resistant anaerobic spores
What does C. Diff produce?
Enterotoxin (A)
Cytotoxin (B)
(C-diff transferase)
What does C. diff do to the gut?
Target enterocytes and cause necrosis which will damage the integrity of the gut
Severity of C. Diff
Ranges from mild diarrhoea to severe colitis
Treatment of C. Diff
Stop precipitating antibiotic (if possible)
Methonidazole (oral if no severity markers)
Oral vancomycin (if two or more severity markers)
Fidaxomicin
Stool transplants
Surgery may be required
Complications of C. diff infection
Pseudomembranous colitis
Prevention of C.diff infection
Reduction in broad spectrum antibiotic prescribing
Avoid 4Cs
Antimicrobial management team (AMT) and local antibiotic policy
Isolate symptomatic patients (due to spores spreading rapidly)
Wash hands in between patients (spores not affected by gels)
4Cs to avoid in the prevention of C. Diff infection
Cephalosporins Co-Amoxiclav Clindamycin Clarithromycin (Ciphrofloxacin)
What are protozoa and helminthes (parasites) generally diagnosed by?
Microscopy
Examples of UK parasites
Giardia lamblia
Cryptosporidium parvum
Where is giardia lamblia found?
Contaminated water
Presentation of giardia lamblia
Diarrhoea Malabsorption (vit B12) Failure to thrive Flatulence Greasy stools that are foul smelling
Definition of diarrhoea
A subjective term describing frequent loose/liquid stools
Definition of foodstuffs
Gastroenteritis caused by contaminated foodstuffs
Definition of dysentery
Infections of the intestines resulting in pain and often bloody/mucoid diarrhoea
What infections of viruses/parasites/bacteria cause localised infection in GI lumen?
Cholera
Rotavirus
Norovirus
What infections of viruses/parasites/bacteria cause toxin mediated disease?
E.coli 0157
C. Diff
Staphylococcus aureus
What infections of viruses/parasites/bacteria cause systemic infection +/- bacteraemia?
Campylobacter
Entamoeba Histolytica
How do you catch E. Coli 0157?
Agriculture
Animal faeces exposure
What does enterotoxigenic E. coli cause?
Travelers Diarrhoea
How do you catch salmonella spp?
Contaminated animal products
tortoises/terrapins/reptiles
How do you catch campylobacter spp?
Contaminated chicken
How do you catch Clostridium Difficle infection?
Broad spectrum antibiotic usage
How do you catch Vibrio Cholerae?
Contaminated water in developing countries/crisis zones
Which bacteria is associated with Guillian Barre syndrome?
Campylobacter jejuni/coli
What is E. Coli 0157 associated with?
Haemolytic Uraemia Syndrome
What can C. diff infection lead to?
toxic megacolon, perforation and death
What post infective condition can salmonella lead to?
IBS
What organism causes cholera?
Vibrio Cholerae
Where is entamoeba histolytica found?
Foreign travel to areas of poor hygiene
What can entameoba histolytica result in (complication)?
Amoebic liver cysts
What does entameoba histolytica cause?
Ameobic dysentery
When would blood cultures be carried out?
To exclude invasive campylobacter/salmonella
When would toxin testing be carried out?
To confirm C. Diff infection
When would stool cultures be carried out?
To isolate bacterial pathogens e.g. campylobacter, salomonella, shigella, E. coli
When would stool microscopy be carried out?
Parasitic causes - looking for ova, cysts and parasites along with relevant travel history
When would Viral PCR/antigen testing be carried out?
To confirm norovirus/rotavirus infection
How to assess fluid status in an infected patient?
Fluid balance (in/out) BP and HR (postural drop in BP is very sensitive for fluid depletion) mucuous membranes (dry vs moist) Weight (assess trend) Leg raising test Skin turgor
Using antibiotics when infected with what can make the infection worse?
E. Coli 0157
Two forms of giardia lamblia
- Hard cyst
- when in stable environment - Trozozytes
- in the gut the cyst exocytes itself into two trozozytes which live in the duodenum - when they get back into the colon they endocyst themselves back into cysts
Where are giardia lamblia cysts seen?
On stool microscopy
Where is the “vegetative form” of giardia lamblia seen?
Duodenal biopsy
“String test”
Treatment of giardia lamblia
Metronidazole
Where is cryptosporidium parvum found?
Contaminated water (animal faeces) - have to filter water as not affected by chlorine
Where are the cysts of cryptosporum parvum seen?
Microscopy
Treatment for cryptosporum parvum
No treatment
Cryptosporum parvum has a particular problem in who and why?
Immunocompromised patients, it can move loads of places in these patients e.g. pancreatic ducts, resp systems
What does entamoeba histolytica form?
8 trophocytes
What does entamoeba histolytica cause/presentation?
Ameobic dysentery - causes blood + mucus in stool
Can cause different ranges of damage
- mild inflammation which is asymptomatic to
- deep infiltration into portal circulation and so flow into brain, liver etc
vegetative form in symptomatic patient - “hot stool”
Cysts seen in asymptomatic patient
Ameobic liver abscess (long term complication - “anchovy pus”
Treatment of entaemeba histolytica
Metronidazole
What strains of adenovirus cause diarrhoea?
40/41
Who gets the rotavirus?
Children < 5 years
When is rotavirus common?
Winter
How is rotavirus diagnosed?
Antigen detection
Transmission of norovirus
Faecal-oral route
Ingestion of aerosol particles from vomit in surrounding air
outbreaks of norovirus are common where?
In isolated areas e.g. cruise ships, community, hospital
Diagnosis of norovirus is done by…
PCR
How infectious is norovirus?
Very infectious - do not need many viral particles to pass on the infection
Defence against enteric infections
Hygiene
Stomach acidity (antacids + infection)
Normal flora (C. Diff diarrhoea)
Immunity (HIV - salmonella)
Diarrhoeal illness is predominately one of two pictures
- Secretory
2. Inflammatory
An example of non-inflammatory secretory diarrhoeal illness would be….
Cholera
An example of an inflammatory diarrhoeal illness would be….
Shigella dysentery
An example of a mixed picture of inflammatory and secretory diarrhoeal illness would be…
C. Difficle diarrhoea
Presentation of non-inflammatory diarrhoeal illness
Frequent watery stools with little abdominal pain
Pathology of cholera as a secretory-toxin mediated infection
Increased cAMP levels
Increased Cl secretion
Rise in osmotic pressure in gut lumen so lose a lot of fluid
Definition of travellers diarrhoea
Any diarrhoea that occurs on holiday
Treatment of non-inflammatory secretory diarrhoea
Rehydration
Presentation of an inflammatory diarrhoeal illness
Diarrhoea with pain and fever
Pathology of an inflammatory diarrhoeal illness
Inflammatory toxin damage and mucosal destruction
Treatment of inflammatory diarrhoeal illness
Antimicrobials may be appropriate but rehydration alone is often sufficient
Over how many days of the history does it mean it is unlikely to be gastroenteritis?
> 14 days
Things to ask in the history of diarrhoeal illness
Dietary
Contact
Travel
Features of dehydration and inflammation in babies/children
fever raised WCC sunken eyes and cheeks few/no tears Decreased skin turgor sunken fontanelle Sunken abdomen Dry mouth/tongue
Investigations of diarrhoeal illness
Stool culture (3) Blood culture (invasive or not) Renal function Blood count (neutrophilia, haemolysis) Abdominal X ray if distended or tender
Secretory diarrhoea fluid and electrolyte loss
1-7l fluid per day containing 80-100mmol Na
Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions
Hypokalaemia due to K loss in stool (40-80mmol/l of K in stool)
In E. Coli 0157, what does O stand for?
Somatic antigen
How to catch E. coli 0157
Contaminated meat
Person-to-person spread (low inoculum)
Can be imported
Strong link to cattle and slurry
Presentation of E. coli 0157 infection
Frequent bloody stools
Pathogenesis of E. Coli 0157
Produces (verocyto-) toxin
Stays in gut but toxin gets into the blood
Toxin can cause haemolytic uraemic syndrome (HUS)
What does haemolytic uraemic syndrome (HUS) consist of?
Renal failure
Haemolytic anaemia
Thrombocytopenia
Forms of E. Coli that cause diarrhoea
0157
Enteropathogenic
Enterotoxic (travellers diarrhoea)
Enteroinvasive
Diagnosis of E. coli strains
Routine diagnosis not possible
Only E. coli 0157 is easily distinguishable from “ordinary” E . coli
Treatment of E. coli infection
Supportive
Antibiotics NOT indicated
Pathology of haemolytic uraemic syndrome
Toxin binds to globotriaosylceramide
Platlet activation stimulated
Micro-angiopathy results
Attach to endothelial, glomerular, tubule and mesangial cells
