Gastroenteritis Flashcards
epidemiology of gastroenteritis
poor sanitation and hygiene travel contacts - human and animal food - time, storage, reheating, washing, importation acid suppression immunosuppression microbiome genetics
risk factors for GI infection
malnutrition closed/semi-closed communities exposure to contaminated food/water/travel winter congregating/summer floods age<5, not breastfeeding elderly
pathogen infections common with acid suppression
Yersinia enterocolitica, Helicobacter pylori
Clostridium difficile
Vibrio cholera, non-typhoidal Salmonella, Campylobacter jejuni, Listeria, some E.coli
pathogen infections common with immunosuppression
Salmonella, Campylobacter, Shigella
Other organisms that are uncommon in immune competent
pathogen infections common with genetic differences
IL8 promoter variants and severe Clostridium difficile
O blood group and Vibrio cholerae
what is an inoculum
a substance introduced into the body to create or increase the body’s resistance or immunity to a disease
low infectious doses make spread of infection easier
pH affects the required dose
scoring system for diarrhoea
bristol stool chart
what is gastroenteritis
illness caused by eating food contaminated with micro-organisms such as bacteria, viruses and parasites
invasion tissue +/- toxin production
large volume tends tone small bowel
symptoms of gastroenteritis
diarrhoea associated with blood and mucus
fever
abdominal pain
rectal tenesmus
what is dysentery
a type of gastroenteritis - inflammation of intestine (especially colon)
what bacteria is dysentery caused by
shigella
campylobacter
Yersinia enterocolitica - may mimic appendicitis as it may invade mesenteric nodes
pathogens implicated in foreign travel causing gastroenteritis
E.Coli
Vibrio species
rotavirus
pathogens implicated in antibiotics causing gastroenteritis
C diff
pathogens implicated in day exposure causing gastroenteritis
rotavirus
pathogens implicated in anal sex causing gastroenteritis
shigella
salmonella
campylobacter
pathogens implicated in outbreaks causing gastroenteritis
norovirus
contaminated water/food - E.coli, salmonella, campylobacter
describe bacillus cereus
gram positive bacillus
heat resistant spores
short incubation; 1-6 hours
where Is bacillus cereus found
starchy foods - reheated rice
describe staph aureus
gram positive coccus
performed toxin in food - rapid absorption
short incubation; 1-6 hours
describe performed toxin of staph aureus
acts on vomiting centre in brain
vomiting/abdominal pain
where is staph aureus found
foods left at room temperature - milk, meat, fish
tests for gastroenteritis
stool sample
selection from normal bowel flora
enrichment for small number
genetic methods
action of shigella toxin
binds to receptors four on renal cells, RBS and others
inhibits protein synthesis - causing cell death
describe shigella toxin
type 1 and type 2 - 2 more potent
E.coli produces shiga-like toxins
describe shiga-toxin producing E.coli
competes with normal bacterial bowel flora
action of shiga-toxin producing E.coli
adheres to intestinal epithelial cells and elaborates shiga toxin
enters the cell, and irreversibly inhibit protein synthesis - resulting in death of enterocytes.
entry of shiga-toxin into the bloodstream
via damaged intestinal epithelium
causes death of vascular endothelial cells by inhibiting protein synthesis
endothelial cell lysis by shiga-toxin
accompanied by platelet activation and aggregation, cytokine secretion, vascular contraction contributing to fibrin deposition, and clot formation within capillary lumen.
complications of gastroenteritis
haemolytic uraemic syndrome (HUS) - a complication of E.Coli
how does HUS arise
associated primarily with serotypes that produce shiva toxin 2
may develop after diarrhoea has stopped
symptoms of HUS
abdominal pain fever pallor petechiae oliguria diarrhoea + blood
signs of HUS
high WBC low platelets low Hb red cell fragments LDH>1.5
tests for HUS
stool culture - blood faeces U&E FBC film LFT clotting urine lactase dehydrogenase
treatment for HUS
no antibiotics
no anti-motility agents
no NSAIDS
complications of HUS
acute renal failure
thrombocytopaenia
haemolytic anaemia
