Gastroenteritis Flashcards
what are common causative organisms of gastroenteritis
campylobacter (commonest)
salmonella
(outbreaks)
E coli 0157
C.diff, listeria, shigella, norovirus, rotavirus
how is gastritis mostly treated
supportive treatment- no antibiotics
how is it spread
faecal- oral transmission
what are the GI infection risk factors
malnutrition (micro nutrient deficiency), closed/ semi closed, exposure to contaminated food/ water/ travel, winter congregating, age <5, or elderly, acid suppression, immunosupression, microbiome, genetics
what organism is more common in acid suppression
C. diff
what bacterial factors allow them to infect patients
adherence/attachment to the gastrointestinal mucosa,
cellular invasion,
production of exotoxins,
changes in epithelial cell physiology,
loss of brush border digestive enzymes, and/or cell death,
increased intestinal motility, net fluid secretion, influx of inflammatory cells, and/or intestinal hemorrhage
what is the inoculum size
median infecting dose required to cause disease in 50%- low inoculum means easier spread
what affects inoculum size
pH and gastric mobility
what is diarrhoea
> 3 unformed stools a day (a departure from normal bowl habit) with no other cause (laxatives, drig abuse, stimulants) where the stool holds the shape of the container
what is dysnetry
gastroenteritis
what is gastroenteritis
An illness caused by eating food contaminated with micro-organisms, toxins, poisons etc
- inflammation of the intestine, particularly the colon, causing diarrhea associated with blood and mucus
what are the symptoms of gastroenteritis
diarrhoea with blood and mucus, fever, abdominal pain, rectal tenesmus (sense of incomplete defecation), frequent bowl movements
what is the acute duration of gastroenteritis
<2 weeks
how might yersinia enterocolitica mimic appendicitis
as it may envade mesenteric nodes
how can food cause gastroenteritis
cross contamination, waiting too long to eat, inadequate heating and cooling, contaminated environment, poor personal hygiene
why most spores be considered in cooking
as can survive the adverse conditions of many cooking methods
what does a large volume of bowl movements tent to mean
it comes from the small bowel- small volume= large bowel
describe the diarrhoea produced by cholera
large volume of rice water diarrhoea
what are factors that could mean a likelihood of gastroenteritis
foreign travel, recent camping or antibiotics, exposure to daycare or raw sea food, anal receptive sex, HIC positive status, outbreaks
why does gastroenteritis a very short incubation period
as pathogens pre form toxins
what organism cause gastroenteritis with an incubation period of 1-6 hours
bacillus cereus (gram +ve bacillus) found in starchy foods
staph aureus (pre formed toxin in food which acts on vomiting centre in the brain) gram +ve coccus- foods left at room temp
how does the lab identify the causative organism
traditional methods (culture), molecular methods (e.g. microarrays), viral pathogen PCR
why must you put details of the patients history on a stool sample
so lab can look for more specific causes
where is shigella common
refugees/ institutionalisation/ military
what does shiga toxin do
binds to receptors in renal cells, RBC and others- inhibits protein synthesis and causes cell death
what toxins does shigella produce
type 1 and type 2 (more potent)
what can produce shiga like toxins
other bacteria
what is a STEC
shiga like toxin producing e coli
what ecoli should be considered in association with shiga like toxin
e coli 0157
how can shiga toxin e coli cause blood clotting
Shiga toxins can then enter the bloodstream via damaged intestinal epithelium and cause the death of vascular endothelial cells by the same mechanism as absorptive enterocytes.
Endothelial cell lysis is accompanied by platelet activation and aggregation, cytokine secretion, vascular constriction contributing to fibrin deposition, and clot formation within the capillary lumen.
how can STEC cause HUS and what is it
haemolytic uraemic syndrome- toxins in blood are carried to the kidneys causing hematuria and renal failure
when should you suspect E coli 0157
bloody diarrhoea, food, person to person, very low infectious dose, children and elderly at highest risk of complications, haemorrhagic colitis
what is VTEC
verotoxin producing e coli
what is the presentation of HUS
Abdo pain, fever, pallor, petechiae, oliguria
bloody diarrhoea in 90% of cases
85% of HUS cases are under 16 years old
High white cells Low platelets Low HB Red cell fragments LDH>1.5 x normal May develop after diarrhoea stopped
how can HUS develop after diarrhoea stops
Toxin related not due to active proliferation of pathogen
what investigations should be done into HUS
stool culture samples, U&E, FBC, film LFT, clotting, urine
how should HUS NOT be treated
NO antibiotics: may precipitate HUS
NO anti-motility agents
NO NSAIDS
ANTIBIOTICS MAKE TOXINS WORSE- DONT GIVE UNTIL YOU KNOW ITS BENEFICIAL
what antibiotics should be given in gastroenteritis
NONE
where should all cases be reported to
health protection unit
what are the different pathotypes of e.coli
entero:
-toxigenic
produces heat stable/ labile toxin
-pathogenic
Synthesises, secretes and inserts its own reseptor into cell membranes, may be asymptomatic
-invasive
watery diarrhoea
-aggregative
travellers diarrhoea
what is the most common caustive pathogen of diarrhoea
campylobacter
what is the incubation period of campylobacter
16-48 hrs
where is campylobacter found
food: poultry, raw milk
what antibiotics are used against campylobacter
macrolide
what is treating e coli 0157 with antibiotics a possible risk factor of
HUS- haemolytic uraemic syndrome
name a subspecies of campylobacter
jejuni
what are the symptoms of campylobacter infection
diarrhoea, pain, blood (30%), fever
what does campylobacter look like
corkscrew appearance with bipolar flagella
what pathogen is found on lizards
salmonella- why HIV, immunosuppressed, sickle cell, malignancy ask to not have reptiles
what organisms cause outbreaks of gastroenteritis
salmonella, E coli 0157
what is the incubation period of salmonella
12-48 hr
where is salmonella found
poultry, meat, raw egg, animal gut
how goes salmonella infect
toxin and envasion
what are the symptoms of salmonella infection
D&V, blood, fever
what does salmonella’s structure contain
flagellum, lipopolysaccharide, O and H antigens
what is the use of serogrouping salmonella
pinpoint source of infection, detecting outbreaks/ contact tracing
why is listeria monoctogenes known as the fridge organism
an in unpasteurised milk products, deli counter
what are the symptoms of gastroenteritis caused by listeria monocytogenes
9-48 hours incubation period
fever, muscle aches, diarrhoea
what are the symptoms of an invasive listeria infection
2-6 weeks later in immunosuppressed
meningitis/ bacteraemia
(why you avoid unpasteurised food when pregnant)
what type of bacteria is listeria
gram +ve rod
how is listeria spread
food borne transmission, mother to child
name two viruses that cause viral gastroenteritis
rotavirus, norovirus, adenovirus, astrovirus
how is viral gastroenteritis diagnosed
stool sample, PCR assay, immunoassay, antigen detection, serology
how is rotavirus spread
person to person, faecal oral, usually in winter
what are the symptoms of rotavirus gastroenteritis
mild to profuse water diarrhoea, shock, fever, vomiting, self limitng
what is the most common cause of gastroenteritis in children under 3 years
rotavirus
what does rotavirus affect in the bowel
absorption and secretion
how big is the infectious dose of rotavirus
low
how is rota virus managed
hydration, vaccine
describe the rotavirus vaccine
oral, live attenuated
what is the winter vomiting bug
norovirus
how is norovirus spread
faecal oral, droplet, person to person, contaminated food/water
what is the reservoir of norovirus
the community circulation
what can happen 48 hrs after cessation of symptoms in norovirus
asymptomatic shedding
what is the incubation period of norovirus
less than 24 hours
how long does norovirus usually last
2-4 days
how is norovirus treated
hydration- usually self limiting
