Lecture 1 Infectious Diarrhoea Flashcards
Define Diarrhoea
Changes in fluidity and frequency of stool
Define Gastro-enteritis
Three or more loose stools/day and accompanying features (abdominal pain, vomiting)
Define Dysentry
Large bowel inflammation, bloody stools
Describe the epidemiology of gastro-enteritis
Contamination of foodstuffs
Poor storage of produce
Travel-related infections e.g. salmonella
Person to person spread- Norovirus
Name defences against enteric infections
- Hygiene
- Stomach acidity- antacids (no protection) and infection
- Normal gut flora- Cl. Difficile diarrhoea
- Immunity- HIV and Salmonella
Clinical features of non-inflammatory diarrhoeal disease (Cholera)
Frequent watery stools with little abdo pain
How does cholera lead to watery stools
increases cAMP levels and Cl secretion and loss from cells along with Na and K
Osmotic effect leads to massive loss of water from the gut
Clinical features of inflammatory diarrhoeal disease (Shigella dysentery)
Inflammatory toxin damage and mucosal destruction leading to bloody stool
What organism may produce inflammatory and inflammatory clinical features
C.difficile
If the symptoms are 2 weeks is it likely to be gastro-enteritis
No
How do you assess the patient?
Risk of food poisoning Assess hydration - Postural BP - Skin turgor - Pulse
Features of inflammation
- Fever
- Raised WCC
What features would you look for in an infant
- Sunken fontanelle
- Few or no tears
- Sunken eyes and cheeks
- Decreased skin turgor
- Dry mouth or tongue
- Sunken abdomen
What investigations would you carry out?
- Stool culture +/- molecular or Ag testing
- Blood culture
- Renal function
- Blood count- neutrophilia, haemolysis (E. coli O157)
- Abdominal X-Ray/CT if abdomen distended, tender
Differential diagnosis of infectious diarrhoea disease
- Inflammatory bowel disease
- Spurious diarrhoea- secondary to constipation
- Carcinoma
What is the incubation time of Campylobacter Gastroenteritis
Up to 7 days
What is the post infection sequelae
Guillain-Barre syndrome, reactive arthritis
When do symptoms of Salmonella Gastroenteritis appear?
<48 hours after exposure
How long does Salmonella Gastroenteritis diarrhoea last
Diarrhoea usually lasts <10 days
Prolonged carriage of Salmonella Gastroenteritis may be associated with what?
Gall stones
How does E.coli cause symptoms
Produces shiga toxin
E.coli stays in the gut but the toxin gets into the blood
Toxin can cause haemolytic-uremic (HUS) syndrome (haemolytic anaemia and renal failure)
What clinical features characterised by
Renal failure
Haemolytic anaemia
Thrombocytopenia (toxin stimulates platelet activation)
How do you treat an E.coli infection
• Treatment supportive, dialysis, transfusion- antibiotics not indicated- can release more toxins into the blood stream
When should antibiotics be given when someone has gastroenteritis
o Immunocompromised
o Severe sepsis or invasive infection
o Chronic illness e.g. malignancy
Describe the routine bacterial culture of gastroenteritis
- Difficult to find pathogen in the midst of complex normal flora
- Selective and enrichment methods of culture necessary- variety of media and incubation conditions
Describe the routine bacterial culture of Campylobacter
- Specialised culture conditions
* C. jejuni/C. coli
Describe the routine bacterial culture of Salmonella
• 2 species recognised
o Salmonella enterica
o Salmonella bongori
Common Salmonella Infections
- Salmonella enteriditis
* Salmonella typhimurium
Occasional causes of food poisoning outbreaks
- Staph aureus (toxin)
- Bacillus cereus (re-fried rice)
- Clostridium perfringens (toxin)
Patients infected with C.difficile usually give a previous history of what
The 4C antibiotics
What type of toxins do C.difficile produce
Enterotoxin (A) and cytotoxin (B) (inflammatory)-
How do you treat a C.diff infection
- Metronidazole
- Oral vancomycin
- Fidaxomicin
- Stool transplants
- Surgery may be required
How do you prevent CDI Prevention
- Reduction in broad spectrum antibiotic prescribing
- Avoid 4 Cs- cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin
- Antimicrobial Management Team (AMT) and local antibiotic policy
- Isolate symptomatic patients
- Wash hands between patients
How is CDI managed?
• Stop precipitating antibiotic
• Follow published treatment algorithm-oral metronidazole if not severity markers
o Raised temp. >38.5
o WCC >15
o Acute rising creatinine
o Suspicion of colitis/ileus/toxic megacolon
• Oral vancomycin if 2 or more severity markers
How are protozoa and helminths infection diagnosed
By microscopy
Send stool with request “parasites, cysts and ova please” or P, C and O
What are the symptoms of Giardia lamblia infection
Abnormal cramps, bloating, nausea and bouts of watery diarrhoea, malabsorption and failure to thrive
What are the causes of Giardia lamblia
Contaminated water
What are the 2 forms of Cryptosporidium parvum (protozoa)
Oocysts and Trophozites
What are the symptoms of Cryptosporidium parvum infection
Watery diarrhoea, nausea and vomiting, abdominal cramps, low grade fever
What are the routes of infection for Cryptosporidium parvum infection
Ingestion of oocysts in faecally contaminated water
What is the most common cause of diarrhoea under 5?
Rotavirus
What are the symptoms of norovirus
Diarrhoea and vomiting
Where are the most common places for outbreaks of norovirus
Hospitals, community and cruise ships
How is norovirus diagnosed
PCR test
