1. Infectious diarrhoea Flashcards
How do you define gastro-enteritis
how do you define dysentery
Three or more loose stools/day
Accompanying fever
large bowel inflammation, bloody stools
How do people contract gastro-enteritis?
Contamination of foodstuffs
Poor storage of produce
Travel related infections
Person to person spread
What are the most common infectious agents that cause gastro-enteritis?
Campylobacter- 6,096
Salmonella- 751
E.coli 0157- 151
What are the best defences against enteric infections?
Hygiene
Stomach acidity
Normal gut flora
Immunity
What are the broad types of diarrhoeal illness?
Non inflammatory/secretory- E.g. Cholera
Inflammatory- e.g. Shigella dysentery
Mixed picture e.g. C-diff
Describe the course of Non inflammatory diarrhoea?
Secretory/toxin mediated, e.g. cholerea increased cyclic AMP levels, drawing out chlorine and with it water. This leads to frequently watery stools with little abdo pain
rehydration is the mainstay of therapy.
Describe the course of inflammatory diarrhoea
There is inflammatory toxin damage and mucosal damage. This leads to pain and fever.
Antimicrobials may be appropriate but rehydration alone is often sufficient
What should you do to assess the patient
Assess the duration- over 2/52 weeks, unlikely to be Infective gastro-enteritis
Assess risk of poisoning (food,diet,contact)
Assess hydration- postural BP, skin turgor pulse
Look for features of inflammation- fever, WCC
What is the major worry in patients with diarrhoea`
Fluid and electrolyte loss
Can lead to hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions
Hypokalaemia due to potassium loss in stool
How do you investigate a patient with diorrhoea
Stool culture +- molecular or Ag testing
Blood culture
Renal function
Blood count- neutrophilia, heamolysis (e.coli 0157)
Abdominal X-ray/CT if abdomen distended/tender
What are your differential diagnosis?
Inflammatory bowel disease
Spurious diarrhoea (secondary to constipation)
Carcinoma
Sepsis (lack of abdo pain, no blood/mucous)
How do you treat gastro-enteritis?
Rehydration therapy
oral- salt/sugar solution
IV- saline
Describe the course of campylobacter gastroenteritis?
Up to 7 days after incubation so dietary history may be unreliable Stools negative within 6 weeks Abdominal pain can be severe Post infection may develop gullain-barre or reactive arthritis Specialised culture conditions Mainly caused by C.jejuni and C.coli chicken milk and puppies cause it Isolated cases rather than outbreaks
How do you look for the casing agent of gastro-enteritis?
Difficult to ind pathogen within normal flora
Selective and enrichment methods of culture necessary- variety of media and incubation conditions
Takes 3 days to complete all tests
Molecular detection and antigen detection
Describe the course of salmonella gastroenteritis
Symptom onset usually <48 hours after exposure
Prolonged carriage of the bacteria
Post infective IBS common
Most common causes are S.enteritidis and s. typhimurium
Describe the course of E.coli 0157
Infection from contaminated meat or person to person spread
Typical illness characterised by frequent bloody stools
E.coli 0157 produces shiga toxin, toxxin goes into blood
May cause heamolytic uremic syndrome
What is haemolytic-uraemic syndrome?
Caused by shiga toxin produced by e.coli 0157
Causes heamoltic anaemia, thrombocytopenia and renal insufficiency
Symptoms abdo pain, bloody diarrhoea, fever, seizures, lethargy
Treatment mainly supportive, dialysis, no antibiotics, plamapharesis
When do you give antibiotics in gastro-enteritis?
Hardly ever
Immunocompromised
Severe sepsis or invasive infection
Chronic illness e.g. malignancy
Describe the course of C.diff
Typically HAI, caused by use of the 4 C’s
Cephalosporins, co-amoxiclav, clindamycin,ciprofloxacin
Produced enterotoxin and cytotoxin
Treat with metronidazole (frist line), oral vancomycin (high risk),
Stop precipitating antibiotics
How do we prevent C.diff?
Avoid broad spectrum antibiotics Avoid 4 C's Antimicrobial management team (AMT) Isolate symptomatic patients Wash hands between patients Clean environments
What do you do if you suspect someone has a parasite?
Microscopy diagnosis
Send stool with request for paracites, cysts and ova (PC and O)
What is giardia duodenalis
Parasite causing cysts, diarrhoea, gas, failure to thrive
Transmitted by animals and food/water with faeces
Duodenal biopsy with parasite tightly bound to villi
Treat with metronidazole
What is Cryptosporidium parvum
parasite causing diarrhoea, N+V, abdo pain
Caused by infected animals and water/food
oocysts seen on microscopy
No treatment required
What is entamoeba histolytica?
Amoebic dysentery
Typically no bowel symptoms, causes liver, brain pleura abscess
intestinal disease metronidazole and luminal agent given to clear colony
What is rotavirus?
Typically affect children under 5
Common in winter
Diagnose by antigen detection in school
What is norovirus?
"winter vomiting bug" Common cause of outbreaks in communities Diagnosed by PCR Very infectious Strict infection control measures needed
