Introduction to Infection - Diarrhoea Flashcards
What is Diarrhoea?
An increased fluidity and frequency of stool
What is Gastro-Enteritis?
Describes diarrhoea in the setting of other symptoms
What are the features of Gastro-Enteritis?
- 3 or more loose stools/day
- Pain
- Blood/mucous in stool
- nausea and vomiting
- fever
What is dysentery?
An infection/inflammation of the large bowel causing a large degree of bloody diarrhoea, abdo pain, N+V and fever
What are the 2 main types of dysentery?
- Bacillary dysentery - caused by shigella bacteria
- Amoebic dysentery - caused by entamoeba histolytica
What are the main causes of gastro-enteritis?
- Contaminated food; e.g. campylobacter in chicken
- Poor food storage/hygiene
- Salmonella in outbreaks and related to travel
- Person to person spread - especially in norovirus
- Viruses are most common
What is the impact of diarrhoeal illness on mortality?
Tiny in the western world, massive in the developing countries
What are our defences against enteric infections?
- Hygiene
- Stomach acid (antacids bad)
- Normal flora (broad abx bad)
- Immunity (HIV and immunosuppression bad)
What is a common bacterial illness for HIV to present with?
Salmonella infection
What are the 3 different types of diarrhoea?
- Non-inflammatory/Secretory (Cholera)
- Inflammatory (shigella dysentery)
- Mixed (C. diff)
What happens in secretory diarrhoea?
Toxins cause an increased secretion of fluid to cause frequent watery stools with little abdo pain.
Cholera increases cAMP levels and Cl secretion; enterotoxigenic E.coli in travellers’ diarrhoea
What is the mainstay treatment for secretory diarrhoea?
Rehydration - mostly ORT
What happens in inflammatory diarrhoea?
- inflammation of the gut mucosa leads to pain and fever
- occurs with bacterial infection and amoebic dysentery
What is the treatment for inflammatory diarrhoea?
- Rehydration alone is often sufficient (ORT)
- May use antimicrobials/abx
What important things do we look for in Hx/Ex of diarrhoeal illness?
- Symptoms/duration - >2/52 then unlikely to be infective
- Food poisoning - diet, contact, travel
- Assess hydration - look out for postural hypotension, skin turgor and pulse
- Look for signs of SIRS - fever and raised WCC
- Watch electrolytes
- Children may also see sunken fontanelles, eyes, cheeks and abdomen and few tears
What investigations may be useful in diarrhoeal illness?
- Stool culture
- Blood culture
- Renal function
- Blood count - neutrophilia/haemolysis
- Abdo X-ray - if abdomen is distended and tender be wary of toxic dilatation and the risk of perforation
What are some possible differential diagnoses for diarrhoea?
- gastro-enteritis/dysentery
- IBD
- Spurious diarrhoea - secondary to constipation
- Cancer
- Sepsis outside the gut (UT or pneumonia)
What signs might suggest that diarrhoea is a result of sepsis from outside the gut?
- lack of abdominal pain/tenderness or localising symptoms
- no blood/mucous in the stools
What are the features of campylobacter gastroenteritis?
- Up to 7 days incubation
- Stools negative within 6 weeks
- can be severe abdo pain
- rarely ever invasive <1%
- Post infection can develop Guillain-Barré or reactive arthritis
What are the main types of campylobacter which we look for?
Campylobacter jejuni
Campylobacter coli
The most common cause of bacterial food poisoning in the UK - usually in isolated cases from chicken, contaminated milk, puppies
What are the features of salmonella gastroenteritis?
- Symptoms usually onset in under 48h after exposure
- Diarrhoea usually for <10 days
- Will rarely have a positive blood culture (<5%) but if it does then suspect HIV
- Carriage in stool can last up to 20 weeks
- Can be associated with gall stones and post-infectious IBS
What are the particular features of salmonella on culture?
- Lactose non-fermenter
- Antigen/biochemical tests
What are the most common salmonella infections in the UK?
Salmonella enteritidus
Salmonella typhimurium
From pet reptiles or abroad
(different from S. typhi and S. paratyphi - enteric fever)
What is the most common form of E.coli in UK gastroenteritis?
E.coli O157
How does E.coli O157 spread?
Contaminated meat or person-to-person
What are the typical features of E.coli O157?
- Frequent, small volume bloody stools
- Abdominal pain
- Stays in gut but toxin gets into the blood where it causes HUS
What is HUS?
Haemolytic Uraemic Syndrome - often in 10 days after E.coli O157 infection.
Renal Failure - Haemolytic Anaemia - Thrombocytopaenia
Where is E.coli O157 more common?
Rural areas - contaminated water supplies, more livestock etc.
What are some other bacteria that we may look for in gastroenteritis?
(Not campylobacter, salmonella or E.coli O157)
- Shigella - highly infectious and easily causes outbreaks
- E.coli - other forms not looked for routinely including enterotoxic E.coli (traveller’s diarrhoea)
- Staph aureus
- Bacillus cereus (reheat)
- Clostridium perfringens
When should you give antibiotics in gastroenteritis?
If... - Immunocompromised - Severe sepsis - Valvular heart disease - Chronic illness - Diabetes
What causes Clostridium difficile diarrhoea?
C.diff infection due to broad spectrum antibiotic use
5 C’s; cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin and clarithromycin
How do you treat C.diff infection?
- Rehydration
- Metronidazole in minor
- Oral vancomycin (not absorbed)
- Fidaxomicin
- Stool transplant
- Colectomy
How does C. diff cause diarrhoea?
Two toxins:
- Enterotoxin (secretory)
- Cytotoxin (inflammatory)
What test do you ask for if you suspect parasite cause?
Microscopy: Parasites, cysts and ova
What are some common UK parasites?
- Giardia lamblia - contaminated water (metronidazole)
- Cryptosporidium - common in AIDS and immunocompromised (no treatment, report)
What are some imported parasites?
Entamoeba histolytica - amoebic dysentery - liver abscess - treat with metronidazole
What are some causes of viral diarrhoea?
- Rotavirus in under 5s
- Adenoviruses
- Noroviruses - outbreaks in hospital, community, cruise ships
How does norovirus spread?
Contact and aerosol spread
