Diarrhoea Flashcards
What is diarrhoea?
Subjective - increase in fluidity or frequency of stools
How is gastroenteritis defined?
3 or more loose stools in 24 hours plus one of; fever vomiting pain blood/mucus in stools
What is dysentery?
Large bowel inflammation, resulting in severe diarrhoea with blood/mucus in stools
What are the main bacteria responsible for causing diarrhoea in the UK?
Salmonella
Clostridium difficile
Campylobacter
E. coli O157
What campylobacter species are most commonly responsible for causing diarrhoea in the UK?
C. jejuni
C. coli
What is the commonest cause of bacterial food poisoning in the UK?
Campylobacter
What are the sources of campylobacter causing food poisoning?
Chickens
Contaminated milk
Puppies
What pattern of infection does campylobacter result in?
Isolated cases rather than outbreaks - person-to-person spread is rare, outbreaks would have to result from a common contaminated source
Symptoms/signs of campylobacter infection
Severe abdominal pain
Colitic picture e.g. pain, diarrhoea
How long does it usually take a campylobacter infection to clear?
3 weeks
How are Salmonella species screened for?
Screened out as lactose non-fermenters, followed by antigen and further biochemical tests
Most serotypes of salmonella causing diarrhoea are of the same species - what is this?
Salmonella enterica
What are the commonest isolates of salmonella species causing diarrhoea in the UK?
Salmonella enteritidis
Salmonella typhimurium
What salmonella species cause enteric fever rather than gastroenteritis?
S. typhi and S. paratyphi
Features of salmonella gastritis
Symptom onset usually < 48 hours after exposure
Diarrhoea usually lasts < 10 days
Features of blood and stool cultures in patients with salmonella gastroenteritis
< 5% will have positive blood cultures
20% of patients will still have positive stool cultures at 20 weeks
What might prolonged carriage of salmonella be associated with?
Gallstones
What is a common post-infective side effect of salmonella gastroenteritis?
Post-infectious irritable bowel
What kind of bacteria is E. coli O157?
Enterohaemorrhagic gram negative bacilli
What is the source of E. coli O157?
Cattle reservoir
When does excretion of E. coli O157 typically occur?
3 weeks after symptoms
What is the time frame between onset of diarrhoea and HUS in E. coli O157 infection?
5-9 days
Shigella infection is largely a disease of
childhood and travel
What kind of bacteria is shigella?
Gram negative anaerobic
What is leading to the resistance of Shigella?
Widespread quinolone use against shigellosis in the developing world
What would be typical of a history of a patient with clostridium difficile diarrhoea?
History of previous antibiotic therapy - particularly the four C antibiotics (clindamycin, cephalosporins, co-amoxiclav, ciprofloxacin)
How do antibiotics increase the risk of C. diff diarrhoea?
Knock out the normal gut flora, reducing competition for C. diff
Range of severity of C. diff diarrhoea
Ranges from mild diarrhoea to severe colitis, which can result in death particularly in the elderly or those with co-morbidities
What toxins are produced by C. diff?
Enterotoxin A
Cytotoxin B
These cause damage to the colonocytes
What is the treatment of C. diff diarrhoea?
Further antibiotic therapy
Metronidazole Oral vancomycin Fidaxomicin (new and expensive) Stool transplants Surgery
Why is oral vancomycin a suitable treatment for C. diff diarrhoea?
It is not absorbed anywhere else in the GI tract so produces a local effect on colon
What might C. diff diarrhoea result in?
Pseudomembranous colitis
What account for 80% of tourist infections (traveller’s diarrhoea)?
Enterotoxigenic E. coli
Campylobacter
Shigella
What fraction of travellers from industrialised to developing countries will develop a bout of diarrhoea?
about 1/3
How long does traveller’s diarrhoea normally last?
Usually lasts < 1 week Persistent diarrhoea (> 30 days) occurs in 1-3% Significantly shortened by antibiotics
What other bacteria less commonly cause diarrhoea?
Shigella (shigella sonnei in nurseries)
Several other forms of E. coli
What other organisms are occasionally responsible for causing food poisoning outbreaks?
Staphylococcus Aureus
Bacillus Cereus
Clostridium Perfringens
How is routine bacterial culture of stools carried out?
Routinely look for four pathogens
Selective and enrichment method
Takes 3 days to complete all tests
Difficult to find pathogen in the complex flora
What are the parasites commonly detected in stool specimens in the UK?
Protozoa
Helminths
Giardia Lamblia
Cryptosporidium Parvum
Diagnosis by microscopy
What percentage of diarrhoea in developed countries are cryptosporidiosis species responsible for?
3-6%
How is cryptosporidiosis transmitted?
Water-borne outbreaks
Cattle are the principal reservoir
Features of cryptosporidiosis infection in the immunocompromised
Self limiting but protracted illness
Transmission and treatment of Giardia infection
Present in surface water
Asymptomatic carriers
Treatment with metronidazole/tinidazole
What disease might entamoeba histolytica mimic?
Ulcerative colitis
How is symptomatic entamoeba histolytica infection treated?
10/7 metronidazole
Furamide for cyst carriage
Features of Giardia Lamblia infection
Spread in infected water
Diarrhoea, malabsorption and failure to thrive
Vegetative form in duodenal biopsy or string test
Cysts seen on stool microscopy
Treatment of Giardia Lamblia infection
Metronidazole
In what patients was cryptosporidium first recognised?
Patients with AIDS
Features of Cryptosporidium Parvum infection
Spread in contaminated water (from animal faeces)
Cysts seen on microscopy
No treatment
Features of infection due to imported parasites
Vegetative form in symptomatic patient
Cysts seen in asymptomatic patient
Amoebic liver abscess as long-term complication
Treatment with metronidazole
At what time of year is viral diarrhoea most common?
Winter
How is viral diarrhoea diagnosed?
Antigen detection
Common causes of viral diarrhoea
Rotavirus
Adenovirus
Norovirus
In what settings is viral diarrhoea due to norovirus most common?
Hospitals
Community
Cruise ships
etc.
How is norovirus infection diagnosed?
Viral DNA PCR
Treatment of norovirus infection
Supportive
Ward closures
Strict infection control measures
What is food poisoning?
Illness caused by bacteria or other toxins in food, typically with vomiting and diarrhoea
What is gastroenteritis?
Inflammation of the stomach and intestines, typically resulting from bacterial toxins or viral infection and causing vomiting and diarrhoea
What is dysentery?
Infection of the intestines resulting in severe diarrhoea with the presence of blood and mucus in the faeces
What is colitis?
Inflammation of the colon
What factors affect the host’s natural defence against enteric infection?
Age Hygiene Gastric acid Gut motility Normal flora Gut immunity
Possible sources of infection causing gastroenteritis
Contamination of foodstuffs - intensity of farming
Storage of produce e.g. bacterial proliferation to infective doses at room temperature
Travel related infections e.g. Salmonella
Person-to-person spread e.g. norovirus
What percentage of the population will have an infectious intestinal disorder each year?
25%
What percentage of the population will visit their GP due to a GI infection each year?
2%
What is the commonest cause of gastroenteritis?
Viral infection
Campylobacter is the most common bacterial pathogen
What is the most common viral cause of gastroenteritis?
Rotavirus
How many deaths are caused yearly by rotavirus in children under 5?
> 800,000
What is the route of transmission of rotavirus?
Faecal-oral
How does rotavirus result in gastroenteritis?
Infects mature enterocytes of the villous body and tip resulting in cell death and lactose intolerance
How many cases of food poisoning from known pathogens are there per year?
more than 500,000
What is the most common food-borne cause of food poisoning?
Campylobacter
How can C. diff infection be prevented?
Reduction in broad spectrum antibiotic prescribing
Avoid the 4C antibiotics
Antimicrobial management team and local antibiotic policy
Isolate symptomatic patients
Ensure hand washing between patients
Management of C. diff infection
Stop the precipitating antibiotic if possible
Oral metronidazole if no severity markers are present
Oral vancomycin if 2 or more severity markers are present
Mechanisms by which infecting organisms can cause diarrhoea
Toxin mediated
Invasion
Attachment
Features of non-inflammatory diarrhoea
Secretory toxin mediated e.g. cholera or enterotoxigenic E. coli Frequent watery stools Little abdominal pain Rapid dehydration Treated with rehydration therapy
Features of inflammatory diarrhoea
Inflammatory toxin damage and mucosal destruction
Pain and fever
Bacterial infection or amoebic dysentery
Rehydration therapy often sufficient, antimicrobials may be appropriate
What percentage of patients given antimicrobials will get diarrhoea?
5-10%
In what percentage of antibiotic-associated diarrhoea is C. diff the causative organism?
10-15%
What percentage of patients carry C. diff when;
coming into hospital
leaving hospital?
Coming into hospital - 7%
Leaving - 28%
What percentage of stool cultures and toxin detection in C. diff infection will have false negatives?
up to 33%
Defences against enteric infections
Hygiene
Stomach acidity
Normal flora
Immunity
Important features when assessing a patient with diarrhoea
Symptoms and their duration
Risk of food poisoning
Assess hydration
Features of inflammation
Over what length of time is diarrhoea unlikely to be due to infective gastroenteritis?
> 2 weeks
Important aspects of history when determining risk of food poisoning
Dietary Contact Travel history Occpation Institution
Ways to assess hydration
Postural BP Skin turgor Urine flow Patient appearance Muscle cramps
Features of inflammation
Fever
Raised WCC
Tachycardia
Raised respiratory rate
How to assess children for dehydration
Skin turgor
Sunken eyes, cheeks, fontanelle
Few or no tears produced
Dry mouth/tongue
How does diarrhoea affect fluids and electrolytes?
Fluid and electrolyte loss, can be severe in secretory diarrhoea
Hyponatraemia due to sodium loss with fluid replacement
Investigations commonly done for patients with diarrhoea
Stool culture Blood culture Renal function Blood count Sigmoidoscopy Abdominal x-ray
Differential diagnoses for diarrhoea
Inflammatory bowel disease Spurious diarrhoea Carcinoma Obstructive pathology Sepsis
Common treatments of diarrhoea
Rehydration
Fasting
Antimicrobials
Treatment of complications
Features of campylobacter gastroenteritis
Up to 7 day incubation Stools negative within 6 weeks Abdominal pain very severe < 1% invasive Post-infective sequelae
When are antibiotics indicated in the treatment of gastroenteritis?
Immunocompromised patients Severe sepsis or invasive infection Valvular heart disease Chronic illness Diabetes
Typical characteristics of E. coli O157 infection
Frequent bloody stools
Not dehydrated as severely as in other forms of diarrhoea
Abdominal pain
What is haemolytic-uraemic syndrome (HUS) and how is it caused by E. coli O157?
Haemolytic anaemia, renal failure and thrombocytopenia
E. coli O157 produces verocytotoxin which gets into the blood and causes HUS
Characteristics of HUS
Haemolytic anaemia which may result in breathlessness and fatigue Renal failure Thrombocytopenia Low platelet count Lactate dehydrogenase
What is the treatment of HUS? In what groups of patients are complications more common?
Treatment is supportive, antibiotics not indicated
Commoner in the very young, elderly, or those with co-morbidities
Within what time frame will HUS occur following E. coli O157 infection?
Within 10 days of diarrhoea onset
Pathophysiology of haemolytic-uraemia syndrome
Toxin binds to globotriaosylceramide Platelet activation stimulated Micro-angiopathy Attachment to endothelial, glomerular, tubule and mesangial cells Progressive uraemia/renal failure
