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GI lectures > Gastroenteritis > Flashcards

Gastroenteritis Flashcards

1
Q

what are the most important bug to know about?

A 
campylobacter
salmonella
E.coli 0157
C.diff
listeria
shigella
norovirus
rotavirus
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2
Q

describe the global impact of gastroenteritis?

A

1.4 million deaths per year

often due to poor hygiene/sanitation, commercialism, food imported, travel etc

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3
Q

what are the main risk factors for GI infection?

A

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

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4
Q

what infections are more common in acid suppression?

A 
Yersinia enterocolotica
H.pylori
C. diff
vibro cholera, non-typhoidal salmonella
campylobacter
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5
Q

what infections are more likely in immunosuppressed?

A

salmonella
campylobacter
shigella

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6
Q

what else can increase risk of GI infection?

A 
microbiome
genetics (IL8 promoter varients - C.diff, O blood group - vibro cholera)
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7
Q

how does inoculum size affect GI infection?

A

median infective does is required to cause disease in 50% of people
low infectious dose makes spread easier

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8
Q

what can affect required dose?

A

pH

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9
Q

what is diarrhoea?

A

> 3 unformed stools per day
must not be another cause (laxatives, drug abuse etc)
stool holds shape of container
New for the patient

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10
Q

what chart can measure type of diarrhoea?

A

Bristol stool chart

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11
Q

what is dysentery?

A

inflammation of the intestine (mainly colon) causing diarrhoea with blood and mucus

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12
Q

what are the symptoms of dysentery?

A 
fever
pain
rectal tenesmus (incomplete emptying)
<2 weeks
may mimic appendicitis
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13
Q

what can cause dysentery?

A

shigella

campylobacter

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14
Q

what is the classic presentation of gastroenteritis?

A 
diarrhoea
abdominal pain
vomiting
cholera = rice water diarrhoea
invasion of tissue +/- toxin production
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15
Q

what bacteria required short incubation (1-6 hours)?

A

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

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16
Q

traditional vs molecular lab identification?

A 
molecular = quicker, no sensitivities, broad range 
traditional = slow, cheaper, more narrow
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17
Q

why must you put all relevant history (eg. travel etc) on paper request for stool sample?

A

so they test for possible atypical causes

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18
Q

what is the standard test for a viral pathogen?

A

PCR

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19
Q

where is shigella more common?

A

developing world
refugees
institutionalisation
military if traveled

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20
Q

what disease does shigella cause?

A

dysentery

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21
Q

is shigella gram +ve or gram -ve?

A

-ve

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22
Q

what are the 4 groups of shigella?

A

A) S. dysenteriae (original)
B) S. flexneri
C) S. boydii
D) S. sonnei

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23
Q

what does shigella do?

A 
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)
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24
Q

what is the connection between shigella and E.coli?

A

> 30 types of E. coli produce shiga like toxins

called STEC or verotoxin producing E. coli, or EHEC

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25
Q

do you give antibiotics straight away in suspected gastroenteritis?

A

NO

26
Q

who is E.coli 0157 most common in?

A

<5s

also common in <16

27
Q

what does a culture negative bloody stool indicate?

A

toxin producing bacteria

28
Q

what bacterial factors can cause disease?

A

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

29
Q

what type of organism may mimic appendicitis?

A

Yersinia enterocolitica

as it invades mesenteric nodes

30
Q

what aspects of food prep can cause bacteria to multiply?

A 
time
temp
food source
moisture
cross contamination of raw/cooked meat
31
Q

what 3 types of organism can cause gastroenteritis?

A

bacteria
virus
parasites

32
Q

what are important components of a history of GI infection?

A 
diarrhoea:
- frequency
- blood
- mucous
- time course
other symptoms
epidemiology (travel contacts etc)
food history
age
comorbidities
medication history
33
Q

what is a pathotype?

A

group of symptoms and disease patterns associated with a type of bacteria

34
Q

what is the pathotype of enterotoxigenic (ETEC)?

A

produces heat labile and heat stable toxin
heat stable toxin similar to cholera and Yersinia toxins
travel related

35
Q

what is the pathotype of EPEC?

A

non breast-fed children
can be asymptomatic
non toxic, non invasive
secretes own receptor into cell membrane

36
Q

what are some other types of E. coli apart from EHEC?

A

ETEC
EPEC
EIEC
EAIC

37
Q

what is the most common cause of gastroenteritis?

A

campylobacter

38
Q

what are the classic features of a campylobacter infection?

A 
16-48 hrs after dodgy food
pain
blood
fever
often from poultry
39
Q

what bug can humans catch from reptiles?

A

salmonella

40
Q

why is salmonella more dangerous in immunosuppressed?

A

can become bacteraemia

41
Q

what is the classic presentation of salmonella?

A

12-48 hours after poultry, meat, raw egg

D&V, blood, fever

42
Q

give an example of an O antigen

A

0 0157 on E. coli 0157

43
Q

what can be used to trace a salmonella outbreak?

A

serogroups

44
Q

what is the “fridge organism”?

A

listeria

45
Q

who is listeria more likely to be invasive in (eg. meningitis)?

A

age>50
pregnant
immunosuppressed (particularly T cell)

46
Q

what is the classic cause of listeria?

A

unpasteurised milk products

deli counter

47
Q

what is the classic listeria gastroenteritis presentation?

A

9-48 hours after ingesting
fever, muscle aches, diarrhoea
mild symptoms in pregnant women

48
Q

what is the classic presentation of invasive listeria?

A

2-6 weeks after ingestion

49
Q

how is listeria diagnosed?

A

gram +ve rod
grows cell in cold (fridge temp)
easier from sterile site (eg blood, CSF) but stool can be used

50
Q

does listeria monocytogenes cause listeria in humans?

A

no

humans usually have lots of neutrophils in response

51
Q

what are the 2 most important viral causes of gastroenteritis?

A

rotavirus

norovirus

52
Q

what is the most common cause of diarrhoea in children < 3 years?

A

rotavirus

lasts a week

53
Q

how is rotavirus spread?

A

person-person
faecal-oral
direct and indirect
usually in winter

54
Q

how is rotavirus treated?

A

usually self limiting

has a vaccine (oral live attenuated)

55
Q

what is norovirus?

A 
winter vomiting disease
highly infectious (common in hospitals, cruise ships, schools)
56
Q

what are the symptoms of norovirus?

A

abrupt and unpredictable onset
D&V sudden and explosive
asymptomatic shedding (48 hrs post cessation of symptoms)

57
Q

how is norovirus treated?

A

short incubation (<24 hrs): lasts 2-4 days
usually self limiting
hydration is key

58
Q

how is norovirus diagnosed?

A

PCR on vomit and stool

59
Q

is all diarrhoea due to an infection?

A

no

60
Q

how can you protect yourself and patients from cross infection?

A

adhere to infection control precautions and prudent antibiotic prescribing
stay off 48hrs post cessation of symptoms

61
Q

what is one health?

A

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

GI lectures (75 decks)

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