Gastroenteritis Flashcards
what are the most important bug to know about?
campylobacter salmonella E.coli 0157 C.diff listeria shigella norovirus rotavirus
describe the global impact of gastroenteritis?
1.4 million deaths per year
often due to poor hygiene/sanitation, commercialism, food imported, travel etc
what are the main risk factors for GI infection?
malnutrition/micronutrient deficiency
closed/semi-closed community
exposure to contaminated food/water/travel
winter congregating (people stay inside in winter so closer together)
summer floods
age <5, not breast feeding
old age
what infections are more common in acid suppression?
Yersinia enterocolotica H.pylori C. diff vibro cholera, non-typhoidal salmonella campylobacter
what infections are more likely in immunosuppressed?
salmonella
campylobacter
shigella
what else can increase risk of GI infection?
microbiome genetics (IL8 promoter varients - C.diff, O blood group - vibro cholera)
how does inoculum size affect GI infection?
median infective does is required to cause disease in 50% of people
low infectious dose makes spread easier
what can affect required dose?
pH
what is diarrhoea?
> 3 unformed stools per day
must not be another cause (laxatives, drug abuse etc)
stool holds shape of container
New for the patient
what chart can measure type of diarrhoea?
Bristol stool chart
what is dysentery?
inflammation of the intestine (mainly colon) causing diarrhoea with blood and mucus
what are the symptoms of dysentery?
fever pain rectal tenesmus (incomplete emptying) <2 weeks may mimic appendicitis
what can cause dysentery?
shigella
campylobacter
what is the classic presentation of gastroenteritis?
diarrhoea abdominal pain vomiting cholera = rice water diarrhoea invasion of tissue +/- toxin production
what bacteria required short incubation (1-6 hours)?
bacillus cereus (gram +ve):
- heat resistant spores from starchy foods (eg. reheated rice)
Staph aureus (gram +ve coccus):
- foods left at room temp
- preformed toxin in food (eg coleslaw) acts on vomiting centre in brain
traditional vs molecular lab identification?
molecular = quicker, no sensitivities, broad range traditional = slow, cheaper, more narrow
why must you put all relevant history (eg. travel etc) on paper request for stool sample?
so they test for possible atypical causes
what is the standard test for a viral pathogen?
PCR
where is shigella more common?
developing world
refugees
institutionalisation
military if traveled
what disease does shigella cause?
dysentery
is shigella gram +ve or gram -ve?
-ve
what are the 4 groups of shigella?
A) S. dysenteriae (original)
B) S. flexneri
C) S. boydii
D) S. sonnei
what does shigella do?
binds to receptors found on renal cells, RBCs and others inhibit protein synthesis causes cell death produces 2 toxins: - type 1 - type 2 (more potent)
what is the connection between shigella and E.coli?
> 30 types of E. coli produce shiga like toxins
called STEC or verotoxin producing E. coli, or EHEC
do you give antibiotics straight away in suspected gastroenteritis?
NO
who is E.coli 0157 most common in?
<5s
also common in <16
what does a culture negative bloody stool indicate?
toxin producing bacteria
what bacterial factors can cause disease?
adherence/attachment to the gastrointestinal mucosa
cellular invasion
production of exotoxins
changes in epithelial pathology
loss of brush border digestive enzymes and/or cell death
increased intestinal motility , net fluid secretion, influx of inflammatory cells, and/or intestinal haemorrhage
what type of organism may mimic appendicitis?
Yersinia enterocolitica
as it invades mesenteric nodes
what aspects of food prep can cause bacteria to multiply?
time temp food source moisture cross contamination of raw/cooked meat
what 3 types of organism can cause gastroenteritis?
bacteria
virus
parasites
what are important components of a history of GI infection?
diarrhoea: - frequency - blood - mucous - time course other symptoms epidemiology (travel contacts etc) food history age comorbidities medication history
what is a pathotype?
group of symptoms and disease patterns associated with a type of bacteria
what is the pathotype of enterotoxigenic (ETEC)?
produces heat labile and heat stable toxin
heat stable toxin similar to cholera and Yersinia toxins
travel related
what is the pathotype of EPEC?
non breast-fed children
can be asymptomatic
non toxic, non invasive
secretes own receptor into cell membrane
what are some other types of E. coli apart from EHEC?
ETEC
EPEC
EIEC
EAIC
what is the most common cause of gastroenteritis?
campylobacter
what are the classic features of a campylobacter infection?
16-48 hrs after dodgy food pain blood fever often from poultry
what bug can humans catch from reptiles?
salmonella
why is salmonella more dangerous in immunosuppressed?
can become bacteraemia
what is the classic presentation of salmonella?
12-48 hours after poultry, meat, raw egg
D&V, blood, fever
give an example of an O antigen
0 0157 on E. coli 0157
what can be used to trace a salmonella outbreak?
serogroups
what is the “fridge organism”?
listeria
who is listeria more likely to be invasive in (eg. meningitis)?
age>50
pregnant
immunosuppressed (particularly T cell)
what is the classic cause of listeria?
unpasteurised milk products
deli counter
what is the classic listeria gastroenteritis presentation?
9-48 hours after ingesting
fever, muscle aches, diarrhoea
mild symptoms in pregnant women
what is the classic presentation of invasive listeria?
2-6 weeks after ingestion
how is listeria diagnosed?
gram +ve rod
grows cell in cold (fridge temp)
easier from sterile site (eg blood, CSF) but stool can be used
does listeria monocytogenes cause listeria in humans?
no
humans usually have lots of neutrophils in response
what are the 2 most important viral causes of gastroenteritis?
rotavirus
norovirus
what is the most common cause of diarrhoea in children < 3 years?
rotavirus
lasts a week
how is rotavirus spread?
person-person
faecal-oral
direct and indirect
usually in winter
how is rotavirus treated?
usually self limiting
has a vaccine (oral live attenuated)
what is norovirus?
winter vomiting disease highly infectious (common in hospitals, cruise ships, schools)
what are the symptoms of norovirus?
abrupt and unpredictable onset
D&V sudden and explosive
asymptomatic shedding (48 hrs post cessation of symptoms)
how is norovirus treated?
short incubation (<24 hrs): lasts 2-4 days
usually self limiting
hydration is key
how is norovirus diagnosed?
PCR on vomit and stool
is all diarrhoea due to an infection?
no
how can you protect yourself and patients from cross infection?
adhere to infection control precautions and prudent antibiotic prescribing
stay off 48hrs post cessation of symptoms
what is one health?
there is many ways we can be exposed to bacteria which are resistant
antibiotic treatment of animals can affect the resistance profiles of bugs that are in contact with humans
