Gastroenteritis Flashcards
What is the estimated metabolic capacity of the normal flora of the gut?
That of the liver
What are example metabolic functions of the commensal flora of the gut?
Produce B12 and VitK
What are other functions of the gut microflora?
Antibody induction, colonisation resistance
What type of bacteria mostly inhabit the gut?
Obligate or facultative anaerobes
Give examples of commensal gut bacteria.
- Bacteroides sp. (Anaerobic GNB)
- Clostridium perfringens (Anaerobic GPB)
- Escherichia coli (Facultative GNB)
- Enterococcus faecalis (Facultative GPC)
What are the common bacterial causes of gastroenteritis?
- Salmonella,
- Shigella,
- E coli
- Campylobacter
- Vibrio cholerae
- Clostridium difficile
- Staph aureus
- Bacillus cereus
What are the common viral causes of gastroenteritis?
- Norovirus
- Rotavirus
What are the common parasitic causes of gastroenteritis?
- Entamoeba hist.
- Giardia lamblia
- Cryptosporidium
What are the clinical features of infective gastroenteritis?
- Acute onset
- Vomiting and/or
- Diarrhoea – frequency, mucous, blood
- Abdominal pain
- Systemic effects – fever etc.
What are the possible complications of infective gastroenteritis?
- Dehydration
- Renal failure
- HUS
- Toxic megacolon
- GBS
- Salmonella
What investigations should be performed for gastroenteritis?
- Bloods – FBC, U&E, CRP, blood cultures
- AXR – if severe
- Stool
- Ova, parasites and cysts ‘OCP’
- Microscopy, culture and sensitivity ‘MC&S’
- Clostridium difficile toxin ‘CDT’
- Viral PCR
What is the main and problematic route of spread of viral gastroenteritis?
Aerosol
What was the source of the largest outbreak of foodborne Cryptosporidium?
Bagged salads.
Which bacteria produce enterotoxins?
- Vibrio cholerae
- Escherichia coil (entertoxigenic – ETEC, verotoxigenic - - VTEC)
- Clostridium perfringens
- Staphylococcus aureus
- Bacillus cereus
- Clostridium difficile
Which bacteria adhere to the bowel wall?
- Shigella sonnei / flexneri
- Escherichia coil (entertoadherent – EAEC)
- Campylobacter jejuni
- Salmonellae
What virulence factor is produced by E. Coli O157 and what does it cause?
Shiga-like toxin - causes haemolytic uraemia syndrome
What is the mechanism of action of Shiga-like toxin?
Toxin activates G protein leading to increased levels of cAMP. Activates ion channels. Overexcrete Chloride ions. Water follows out of cells into bowel. Different toxins have different mechanisms of action but often diarrhoea is caused by an efflux of K or Cl ions, and the resulting water loss by osmosis.
This means that killing bacteria can actually release more toxin, making disease WORSE.
What is the difference between typhoidal and non-typhoidal Salmonella?
Typhoidal has the ability to dissemnate throughout the body.
Why should antibiotics generally be avoided in bacterial gastroenteritis?
Killing bacteria will cause the mass release of pathogenic toxins -> can make the disease much worse.
Can increase the duration of the infection.
What treatment should be given in bacterial gastroenteritis?
Usually supportive treatment and symptomatic relief.
What is the cause of antibiotic-associated diarrhoea?
- Disruption of gut microflora
- Change in metabolism (carbohydrates / bile acids)
- Overgrowth of pathogenic organisms
What are the symptoms of antibiotic-associated diarrhoea?
Symptoms range from mild diarrhoea to pseudomembranous colitis, toxic megacolon, perforation, shock
Aside from the most common organism, C. difficile, what other organisms can cause antibiotic-associated diarrhoea?
- C. perfringens
- S, aureas
- Candida spp.
- Klebsiella spp.
- Salmonella spp.
What is the current treatment for C.diff-associated diarrhoea?
- Oral metronidazole / oral vancomycin
- Both affect gut flora (anaerobes)
- Vancomycin and metronidazole use is a risk factor for VRE selection
- Potential for emergence of resistance to vancomycin / metronidazole in C. difficile
