Infectious Diarrhoea Flashcards
How is gastroenteritis defined clinically?
Three or more loose stools a day
What are the possible accompanying features of gastroenteritis?
Abdominal pain
Bloody diarrhoea
What are the common causes of gastroenteritis?
Most often viral
Most common bacterial cause is camplyobacter species
What is the epidemiology of gastroenteritis?
- Contamination of foodstuffs
- Poor storage of produce
- Travel related infection
- Person to person spread
What are the defences against enteric infection?
Hygiene (most important)
Stomach acidity
Normal gut flora
Immunity
What are the three kinds of diarrhoeal illness?
Inflammatory
Non-inflammatory
Mixed
How are non-inflammatory diarrhoeal illnesses characterised?
Characterised by secretory toxin mediated disease with frequent watery stools with little abdominal pain. The mainstay of therapy is rehydration.
Where is cholera most common?
In situations such as refugee camps where normal population systems are broken down.
How does cholera cause diarrhoea?
The mechanism of diarrhoea in cholera involves an increase of cAMP resulting in a loss of Cl- ions from cells along with K and Na. This causes osmotic effects leading to a massive loss of water from the gut
How are inflammatory diarrhoeal illnesses characterised?
Caused by inflammatory toxin damage and mucosal destruction. This is associated with bacterial infection/ amoebic dysentery and there is usually pain and fever present. Rehydration alone is often sufficient but in some cases antimicrobials may be required.
How is assessment of a patient with diarrhoea done?
- Taking note of their symptoms and duration (if symptoms have been present for >2 weeks then gastro-enteritis is unlikely)
- Risk of food poisoning (dietary, contact, travel history)
- Assess hydration- postural blood pressure (drop of 20 or more deemed significant), skin turgor, pulse
- Features of inflammation (fever, raised white cell count)
What are the signs of dehydration in children?
- Sunken eyes and cheeks
- Decreased skin turgor
- Sunken abdomen
- Few or no tears
- Dry mouth or tongue
- Sunken fontanelle
What are the effects of fluid and electrolyte loss in diarrhoea?
Fluid loss can cause hyponatraemia, which requires replacement with hypotonic solutions.
Hypokalaemia results from loss of K+ in stool
What investigations can be helpful in diarrhoea?
- Stool culture +/- molecular or antigen testing (three cultures recommended but infection usually picked up after one)
- Blood culture
- Renal function
- Blood count
- Abdominal X-ray/CT if abdomen distended or tender
What is included on a differential diagnosis of diarrhoeal disease?
Inflammatory bowel disease
Spurious diarrhoea secondary to constipation
Carcinoma
Sepsis outwith the GI tract (Lack of abdominal pain and tenderness and lack of blood or mucous indicators, most commonly UTI or pneumonia)
Generally, how is gastroenteritis treated?
Treatment of gastro-enteritis is mainly rehydration, which can be IV or oral. Oral rehydration is given with a salt or sugar solution and IV rehydration is given with saline
What are the implications of the long incubation period associated with campylobacter enteritis?
Long incubation period- up to 7 days Dietary history may be unreliable Stools can be negative within 6 weeks of infection Abdominal pain can be severe Very few infections invasive
What are the common post-infection conditions associated with campylobacter?
Guillain-Barre syndrome
Reactive arthritis
What should be done if campylobacter is detected in the blood?
Check the patient’s immune function
Which species of campylobacter cause disease?
Campylobacter jejuni (90%) Campylobacter coli (10%)
How do symptoms of salmonella gastroenteritis present?
Symptoms of salmonella gastroenteritis usually onset around 48 hrs post-exposure. Diarrhoea usually lasts less than ten days
What post-infection condition is common in salmonella gastroenteritis?
Post-infection irritable bowel
What are the species of salmonella and what isolates are most common in the UK?
There are two species of the salmonella genus; salmonella enterica and salmonella bongori. The commonest isolates in the UK are salmonella enteriditis and salmonella typhimurium
How is E.coli O157 transmitted?
From contaminated meat or person-person spread
What are the symptoms of E.coli O157?
Frequent bloody stools
What is the pathology of E.coli O157?
The bacteria causes Shiga toxin, which spreads to the blood whereas E.coli stays in the gut. The toxin can cause haemolytic-uraemic syndrome (HUS), which results in haemolytic anaemia, thrombocytopenia and renal failure. Treatment can be supportive but antibiotics are not indicated.
What are the more rare causes of food poisoning?
Staph aureus Bacillus cereus (re-fried rice) Clostridium perfringens (undercooked meat/food left out)
When are antibiotics indicated in gastroenteritis?
Patient immunocompromised
Severe sepsis
Invasive infection
Has chronic illness (ie malignancy).
What toxins are produced in a C.diff infection?
Enterotoxin
Cytotoxin
How is C.diff infection treated?
Metronidazole Oral vancomycin Fidamoxacin Stool transplants Surgery sometimes required
How can C.diff infection be prevented?
- Reduction in prescription of broad spectrum antibiotic
- Avoid “4 C’s” (cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin)
- Antimicrobial management team
- Isolate symptomatic patients
- Hand hygiene
- Cleaning environment
How is C.diff infection managed?
Stopping the precipitating antibiotic
Oral metronidazole if no severity markers
Oral vancomycin if two or more severity markers
What is parasitology caused by and how is it diagnosed?
Causes of parasitology are protozoa or helminths (worms). Diagnosis is generally done by microscopy. Stool samples should be sent with requests for parasites, ova and cysts
What is the most common cause of viral diarrhoea?
Norovirus
How is norovirus diagnosed?
PCR
What are the complications of E.coli0157 HUS?
Haemolytic anaemia
Thrombocytopenia
Renal failure
