Infectious Diarrhoea - part 1 Flashcards
what is Diarrhoea?
• subjective definition
fluidity and frequency - a change in fluidity and frequency in comparison to normal
what is Gastro-enteritis?
• objective
- three or more loose stools/day
- accompanying features
what is Dysentery?
• obvious
- large bowel inflammation, bloody stools
intestinal inflammation, primarily of the colon. It can lead to mild or severe stomach cramps and severe diarrhea with mucus or blood in the feces
picture of the bristol stool chart
Guide on wards to see if things are getting better or worse
Gastroenteritis tend to have a score of 6 or 7
what is the epidemiology of gastro-enteritis?
- Contamination of foodstuffs - Intensively farmed chicken and campylobacter
- Poor storage of produce - Bacterial proliferation at room temperature
- Travel-related infections e.g. Salmonella
- Person-to-person spread - norovirus
how common are infectious intestinal diseases and how many of them need medical treatment?
- 25% of population have Infectious intestinal disorder each year
- 2% of population visit GP because of GI infection each year
- For each reported case there are 10 GP consults and 147 community cases that are unreported
what are the commonest causes of infectious intestinal diseases?
• Viruses are commonest cause with campylobacter being the commonest bacterial pathogen
only a _____ proportion with infectious intestinal diseases come into hospital
small
what are the trends seen in food poisoning?
- There are more than 500,000 cases of food poisoning a year from known pathogens
- Campylobacter is the most common foodborne pathogen, with about 280,000 cases every year
- Salmonella is the pathogen that causes the most hospital admissions – about 2,500 each year
- Poultry meat was the food linked to the most cases of food poisoning, with an estimated 244,000 cases every year
Global mortality
what are the numbers of the different causes of gastro-enteritis in scotland?
- Campylobacter 6,096 - 112.8 per 100,000 population
- Salmonella 751 - 13.9 per 100,000 population
- E. coli O157 151
What is the defences against enteric infections?
- HYGIENE
- stomach acidity - antacids (If taking antacids then much less protection and more risk) and infection
- normal gut flora (Gut flora protect against infections) - Cl. difficile diarrhoea
- immunity - HIV + salmonella
what is the mos timportant defence against enteric infections?
hygiene
what are the different kinds and clinical features of diarrhoeal illness?
- Non-inflammatory/secretory e.g. cholera
- Inflammatory e.g. shigella dysentery
- Mixed picture e.g. C. difficile
what causes non-inflammatory diarrhoeal illness?
secretory toxin-mediated
- cholera - increases cAMP levels and Cl secretion
- enterotoxigenic E. coli (travellers’ diarrhoea)
what are the clinical features of non-inflammatory diarrhoeal illness?
frequent watery stools with little abdo pain
No inflammation, just frequent watery stools
what is the treatment of non-inflammatory diarrhoeal illness?
rehydration mainstay of therapy
What is the mechanism of diarrhoea in cholera (non-inflammatory)?
Increased cAMP results in loss of Cl from cells along with Na and K
Osmotic effect leads to massive loss of water from the gut
what causes inflammatory diarrhoeal illness?
bacterial infection/amoebic dysentery
what are the clinical features of inflammatory diarrhoeal illness?
inflammatory toxin damage and mucosal destruction
pain and fever
what is the treatment of inflammatory diarrhoeal illness?
antimicrobials may be appropriate but rehydration alone is often sufficient
how do you assess a patient?
- Symptoms and their duration - >2/52 unlikely to be infective gastro-enteritis (may be IBD)
- Risk of food poisoning - Dietary (often unreliable), contact, travel history
- assess hydration - postural BP, skin turgor, pulse
- features of inflammation (SIRS) - fever, raised WCC
Fluid and electrolyte losses - how much is lost?
• Can be severe with secretory diarrhoea - 1-7 l fluid per day containing 80-100 mmol Na
what may occur due to sodium and potassium loss?
Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions
Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)
what are some investigations you may do to assess the pateint?
- stool culture (main stay of investigation) +/- molecular or Ag testing (Molecular techniques to detect toxins)
- blood culture (gets taken in any patient with a fever)
- Renal function
- blood count - neutrophilia, haemolysis (E. Coli O157)
- abdominal X-Ray/CT if abdomen distended, tender (Imaging can demonstrate dilatation of the large bowel)
what are some differential diagnosis?
- Inflammatory bowel disease (if diarrhoea more than 2 weeks and bloody)
- Spurious diarrhoea - secondary to constipation
- Carcinoma
- Diarrhoea and fever can occur with sepsis outside the gut
- lack of abdo pain/tenderness
goes against gastroenteritis - no blood/mucus in stools
What is the treatment of gastro-enteritis?
• Rehydration - iv or oral?
- Oral rehydration with salt/sugar solution
- iv saline
Iv in hospital
In community will depend upon oral rehydration
Glucose and salt together is better than just salt as the transport of glucose is linked to sodium across the cell wall
what are the features of Campylobacter gastroenteritis?
Most common
Up to 7 days incubation so dietary history may be unreliable
Stools negative within 6 weeks
abdominal pain can be severe
<1% invasive
Post-infection sequelae - Guillain-Barre syndrome, Reactive arthritis
what are the features of Salmonella gastroenteritis?
symptom onset usually <48 hrs after exposure
diarrhoea usually lasts <10 days
<5% positive blood cultures
20% patients still have positive stools at 20/52 - Prolonged carriage may be associated with gallstones
Post-infectious irritable bowel is common
How is E.coli O157 spread?
Infection from e.g. contaminated meat or person-to-person spread (low incoulum)
What does E.coli O157 cause?
Typical illness characterised by frequent bloody stools
Prominent bloody stools
Abdominal pain
Not much fever
How does E.coli O157 cause problems?
E. coli O157 produces Shiga toxin (same toxin also produced by Shigella spp) (previously called verocyto- toxin) - Organism it self is not the problem, it’s the toxin
E. coli O157 stays in the gut but the toxin gets into the blood
toxin can cause hemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure)
What are the effects of hemolytic-uraemic (HUS) syndrome and how are they caused?
HUS characterised by renal failure, haemolytic anaemia and thrombocytopenia. Treatment supportive - antibiotics NOT indicated
Toxin stimulates platelet activation and micro-angiopathy results
Micro-angiopathy haemolytic anaemia by clotting of the platelets in the blood vessels so the blood cells are squeezing through these platelet clots and becoming haemolysed
Lose platelets and get renal insufficiency and uraemia
General supportive measures required and no antibiotics needed and may make it worse
E. coli rates
someitmes get spikes
When should I give antibiotics?
Indicated in gastroenteritis for
- immunocompromised
- severe sepsis or invasive infection
- chronic illness e.g. malignancy
Not indicated for healthy patient with non-invasive infection
Vast majority of patients don’t need antimicrobial treatment - Treatment all about maintaining hydration
Summary:
- Gastroenteritis is a common illness which can be diagnosed _______
- A _______ of patients with gastroenteritis are admitted to hospital
- The main stay of treatment is _________ and this can usually be oral rather than iv
- A minority of patients require ________
clinically - Not dependent on microbiological conformation
minority
rehydration
antibiotics
