Infectious diarrhoea Flashcards
What is the definition of diarrhoea?
Increased fluidity & frequency
What is the definition of gastro-enteritis?
3 or more loose stools/ day
Accompanied with abdominal pain & bloody stools)
What occurs with dysentery?
Large bowel inflammation
Bloody stools
What type of stool is diarrhoea classified as by the bristol stool chart?
Type 7
What are some of the causes of gastro-enteritis?
Contamination of foodstuffs (chicken)
Poor storage of produce
Travel related infections
Person to person spread
What is the commonest bacterial pathogen which causes diarrhoea?
Camplyobacter
What are the most common causes of infectious diarrhoea?
Campylobacter
Salmonella
E.coli o157
What are some of the defences against enteric infections?
Hygiene
Stomach acid
Normal gut flora
Immunity
What effect do antacids have on infection?
More at risk of gastro-enteritis due to loss of protective acid
What effect do ABIs have on infection?
Increase risk of C. diff & diarrhoea
What are the 3 main clinical features of diarrhoea illness?
Non-inflammatory/ secretory
Inflammatory
Mixed
What is a secretory (non-inflammatory) form of diarrhoea illness?
Cholera
What is an inflammatory cause of diarrhoea illness?
Shigella dysentery
What infection demonstrates a mixed picture of diarrhoea disease?
C. diff
What is the mechanism of action of secretory toxin-mediated diarrhoea?
Increases cAMP levels & Cl secretion
Osmotic effect leads to massive water loss
What is the main treatment of secretory diarrhoea?
Rehydration therapy
What are the mechanisms of action of inflammatory diarrhoea disease?
Inflammation & toxin damage leads to mucosal destruction
Pain & fever
In a history, when is it unlikely to be infectious diarrhoea?
> 2 weeks duration
How can you assess hydration of patient with diarrhoeal disease?
Postural BP
Skin turgor
Pulse
What are some of the electrolyte imbalances which can occur in diarrhoea?
Hyponatreamia
Hypokalaemia
What investigations could be done in a patient with diarrhoeal disease?
Stool culture Blood culture Renal function Blood count Abdominal Xray
What are some of the differential diagnosis of diarrhoeal disease?
Inflammatory bowel disease
Spurious diarrhoea (secondary to constipation)
Carcinoma
In what incidence can diarrhoea & fever occur?
Sepsis outside the gut
What are some of the treatment options for gastro-enteritis?
Oral rehydration therapy
IV saline
What is the commonest cause of gastro-enteritis?
Campylobacter
How long is the incubation period of campylobacter gastro-enteritis?
7 days
How long does it take for campylobacter to clear from the gut?
6 weeks
Is campylobacter invasive/ non-invasive?
Non-invasive
What are some of the post-infection diseases which can occur following campylobacter gastro-enteritis?
Guillain-Barre syndrome
Reactive arthritis
What are the mechanisms for bacterial culture?
Molecular detection
Antigen detection
What are the 2 types of campylobacter which are most commonly the source of infection?
C. jejune (90%)
C. coli (9%)
What is the commonest cause of bacterial food poisoning in the UK? What are the main sources?
Campylobacter
Chicken, contaminated milk,
When do symptoms of salmonella gastroenteritis occur within?
<48hrs after exposure
How long does Salmonella diarrhoeal disease last?
10 days
How long could stools be positive for salmonella following disease?
20 weeks
What are the most common species of salmonella?
S. enterica
S. bongori
How are salmonella species screened in lab?
Lactose non-fermenters (biochemical testing)
How can E.coli O157 be contracted?
Contaminated meat
Person-to-person
How is E.col O157 typically characterised?
Frequent bloody stool
What toxin is produced by E.coli O157?
Shiga toxin
What is responsible for E.coli O157 infection?
Toxin - moves into the blood
E.coli remains in the gut
What syndrome can the shiga toxin cause?
Haemolytic -uraemic (HUS) syndrome
What is NOT recommended in the treatment of E.coli O157?
ABIs - causes increased lysis of the bug therefore increases the risk of toxin release
What does shiga toxin stimulate in the blood?
Toxin stimulates platelet activation
Micro-angiopathy
What other forms of E.coli cause diarrhoea?
Enteroinvasive
Enteropathogenic
Enterotoxic (travellers diarrhoea)
How can E.coli O157 be distinguished from other strains?
Non-sorbitol fermenting
What are some of the occasional cause of food poisoning outbreaks?
S. aureus
Bacillus cereus (rice)
C. perfringens (meat)
When could ABIs be used in gastroenteritis?
Immunocomprised
Severe sepsis or invasive infection
Chronic illness eg malignancy
When are ABIs not advised in gastroenteritis?
In an healthy patient with non invasive infection
What ABIs are associated with C diff diarrhoea infection?
4Cs : cephalosporin, co-amoxiclav, clindamycin, ciprofloxacin
What are the toxins produced by C. Diff?
Enterotoxin
Cytotoxin
What are the main treatments for C diff infection?
Metronidazole
Oral Vancomycin
Which ABI is normally administered IV but used orally in C. diff infection?
Vancomycin
What important actions should be taken with a patient with C. diff?
Isolate symptomatic patient
Wash hands between patients
Contact precautions
How should you manage C. diff?
Stop precipitating ABIs
Oral metronidazole or vancomycin
What are some examples of parasites?
Protozoa or helminths
How are parasites usually diagnosed?
Microscopy
Stool sample - parasites, cysts & ova (P,C,O)
What symptoms are observed in parasite disease (G. lambia)?
Diarrhoea
Malabsorption
Gas
Failure to thrive
How are parasites transmitted?
Direct contact with animals or people
Contaminated water/ food
How are parasites treated?
Metronidazole
What does entamoeba histolytica cause?
Amoebic dysentery
What parasite causes liver abscess?
Entamoeba histolytica (anchovy pus)
What are the different types of viral diarrhoeal disease?
Rotavirus
Norovirus
Adenovirus
What population does Rotavirus usually affect?
Children under 5 yrs
When did cases of rotavirus decrease significantly?
Introduction of vaccination
Where can outbreaks of norovirus usually occur?
Institutions, hospitals, community & cruise ships
How can norovirus be diagnosed?
PCR
How can spread of norovirus be controlled?
Strict infection control
