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Y2 infection > Infectious diarrhoea > Flashcards

Infectious diarrhoea Flashcards

1
Q

define diarrhoea

A

subjective

change fluidity and frequency of stool in relation to normal

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2
Q

define gasto-enteritis

A

objective - clinical scenario and not dependent on microbiology
3 or more loose stools/day
accompanying features

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3
Q

define dysentery

A

large bowel inflammation

bloody stools

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4
Q

type 1 bristol stool

A

separate hard lumps
like nuts
hard to pass

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5
Q

type 2 bristol stool

A

sausage shaped but lumpy

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6
Q

type 3 bristol stool

A

like a sausage but with cracks on the surface

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7
Q

type 4 bristol stool

A

sausage or snake like

smooth and soft

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8
Q

type 5 bristol stool

A

soft blobs with clear cut edges

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9
Q

type 6 bristol stool

A

fluffy pieces with ragged edges

mushy

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10
Q

type 7 bristol stool

A

watery
no solid pieces
entirely liquid

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11
Q

epidemiology of gastroenteritis

A

contamination of food - intensively farmed chicken and campylobacter
poor storage of produce - bacterial proliferation at room temp
travel related infections e.g. salmonella
person to person spread - norovirus

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12
Q

prevalence of gastroenteritis

A

25% have infectious intestinal disorder each year
2% vitis GP because of GI infection p/a
>500 000 cases of food poisoning p/a from known pathogens

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13
Q

commonest cause of gastroenteritis

A

viruses are commonest cause with campylobacter being the commonest bacterial pathogen (280 000 cases p/a)
salmonella is the pathogen that causes the most hospital admissions (2500 p/a)

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14
Q

what food type is most commonly linked with food poisoning

A

poultry meat

244 000 cases p/a

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15
Q

defences against enteric infection

A

hygiene and adequate cooking
stomach acidity (reduced with antacids and infection)
normal gut flora (C. difficile diarrhoea when normal gut flora is reduced through abx use)
immunity (HIV and salmonella)

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16
Q

clinical features of diarrhoeal illness

A

non-inflammatory/secretory - cholera
inflammatory - shigella dysentery
mixed picture - C difficile

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17
Q

non-inflammatory diarrhoeal illness

A

secretory toxin mediated
frequent watery stools with little abdo pain
rehydration is the mainstay of therapy

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18
Q

examples of non-inflammatory diarrhoeal illness

A

cholera - increases cAMP levels and Cl secretion

enterotoxigenic E coli (travellers’ diarrhoea)

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19
Q

mechanism of diarrhoea in cholera

A

increased cAMP –> loss of Cl from cells along with Na and K
osmotic effect leads to massive loss of water from the gut

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20
Q

inflammatory diarrhoeal illness

A

inflammatory toxin damage and mucosal destruction
pain and fever

antimicrobials may be appropriate but rehydration alone is often sufficient

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21
Q

examples of inflammatory diarrhoeal illness

A

bacterial infection

amoebic dysentery

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22
Q

assessing a patient with gastro-enteritis

A

symptoms and their duration - >2/52 unlikely to be infection GE
risk of food poisoning - dietary, contact, travel hx
assess hydration - postural BP, skin turgor, pulse
features of inflammation (SIRS) - fever, raised WCC

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23
Q

features of gastro-enteritis in infants - clinical features of dehydration

A 
sunken eyes and cheeks 
sunken fontanelle 
few or no tears
dry mouth or tongue 
decreased skin turgor 
sunken abdomen
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24
Q

fluid and electrolyte losses

A

can be severe with secretory diarrhoea
1-7L fluid/day containing 80-100mmol Na
hyponatraemia due to Na loss with fluid replacement by hypotonic solutions
hypokalaemia due to K loss in stool (40-80mmol/L of K in stools)

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25
Q

investigations in a patient with gastroenteritis

A

stool culture +/- molecular of Ag testing
blood culture
renal function
blood count - neutrophilia, haemolysis (E. Coli O157)
abdo X-ray/CT is abdomen distended/tender

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26
Q

differential diagnoses

A

inflammatory bowel disease
spurious diarrhoea - 2y to constipation
carcinoma

diarrhoea and fever can occur w/ sepsis outside the gut - lack of abdo pain/tenderness goes against GE, no blood/mucus in stools

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27
Q

treatment of gastroenteritis

A

oral rehydration w/ salt/sugar solution

IV saline

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28
Q

campylobacter enteritis

A

up to 7 days incubation - dietary hx may be unreliable
stools -ve within 6wks
abdo pain can be severe
<1% invasive - +ve blood cultures (consider underlying pathology)
post-infection sequelae

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29
Q

post-infection campylobacter sequelae

A

Guillain Barre syndrome

Reactive arthritis

30
Q

salmonella gastroenteritis

A

symptom onset usually <48hrs after exposure
diarrhoea usually lasts <10 days
<5% +ve blood cultures
20% still have +ve stools at 20/52 (asymptomatic but can still pass on infection) - prolonged carriage may be associated w/ gallstones
post-infectious irritable bowel is common

31
Q

E. coli O157

A

infection from contaminated meat or person-to-person spread (low inoculum)
typical illness characterised by frequent bloody stools
abdo pain

32
Q

toxin produced by E. coli O157

A

Shiga toxin
E. coli O157 stays in the gut but the toxin gets into the blood
toxin can cause haemolytic uraemic syndrome (HUS) - generally in already compromised pts

33
Q

what is HUS

A

haemolytic uraemic syndrome
characterised by renal failure, haemolytic anaemia and thrombocytopenia

treatment is supportive - abx NOT indicated (may make it worse by destroying E. coli O157 and releasing more toxin into bloodstream)

34
Q

how does E. coli O157 lead to HUS

A

toxin activated platelet activation

micro-angiopathy results

35
Q

when are antibiotics indicated in gastroenteritis

A

immunocompromised pts
severe sepsis or invasive infection
chronic illness e.g. malignancy

not indicated for healthy pt w/ non-invasive infection

36
Q

what abx are used for campylobacter infection

A

macrolides

e.g. clarithromycin, azithromycin

37
Q

what abx are used for salmonella infection

A

many salmonellas are still sensitive to ciprofloxacin

ceftriaxone is used for more resistant salmonellas

38
Q

routine bacterial culture for bacterial gastroenteritis

A

difficult to find pathogen alongside complex normal flora
selective and enrichment methods of culture necessary
takes 3 days to complete all tests

39
Q

routine bacterial culture - campylobacter

A

specialised culture conditions
C. jejuni/ C. coli - commonest cause of bacterial gastro-enteritis in UK
chickens, contaminated milk, puppies
isolated cases rather than outbreaks

requires higher temperatures and lower oxygen levels to grow

40
Q

routine bacterial culture - salmonella

A

Salmonella enterica, salmonella bongori
thousands of serotypes with individual names
isolated in the laboratory - screened out as lactose non-fermenters
serotyping requires further antigen and biochemical tests

41
Q

commonest salmonella infections in UK

A

salmonella enteritidis
salmonella typhimurium
>50% of these are imported from abroad

S. typhi and S. paratyphi cause enteric fever (typhoid and paratyphoid) and not gastroenteritis

42
Q

other causative bacteria

A

Shigella ( 4 species) - outbreaks of Shigella sonnei in nurseries
E coli - part of normal gut flora, most strains non-pathogenic, several strains cause diarrhoea

43
Q

which strains of Ecoli cause diarrhoea

A

enterohaemorrhagic (O157)
enterotoxic (travellers’ diarrhoea)
enteroinvasive
enteropathogenic

routine diagnosis of these E coli strains not possible - only O157 is easily distinguished from “ordinary” E coli

44
Q

occasional causes of food poisoning outbreaks

A 
Staph aureus (toxin)
Bacillus cereus (re-fried rice)
Clostridium perfringens (toxin)
45
Q

C. difficile diarrhoea

A

Clostridioides difficile
patient usually has hx of prev abx treatment (4c abx)
severity ranges from mild diarrhoea to severe colitis

46
Q

what toxins does C difficile produce

A

enterotoxin and cytotoxin

inflammatory

47
Q

how is C difficile treated

A

metronidazole
ORAL vancomycin
fidaxomicin
stool transplants

surgery may be required

48
Q

C difficile infection prevention

A

reduction in broad spectrum abx prescribing
avoid 4 Cs
antimicrobial management team (AMT) and local abx policy
isolate symptomatic pts
wash hands between pts - soap and water

49
Q

what are the 4 Cs

A

cephalosporins
co-amoxiclav
clindamycin
ciprofloxacin

50
Q

management of C diff infection

A

stop precipitating abx (if possible)
follow published treatment algorithm - oral metronidazle if no severity markers
oral vancomycin is 2 or more severity markers

51
Q

what are the severity markers

A

raised temp >38.5
WCC >15
acute rising creatinine
suspicion of colitis/ileus/toxic megacolon

52
Q

parasitology

A

protozoa and helminths
diagnosis generally by microscopy
send stool with request “ parasites, cysts and ova” (P,C and O)

53
Q

UK parasites

A

Giardia lamblia

cryptosporidium parvum

54
Q

Giardiasis

A

abdominal cramps
bloating
nausea and bouts of watery diarrhoea
malabsorption and failure to thrive

55
Q

Giardia lamblia

A

(aka G. duodenalis/intestinalis)
protozoa

contaminated water

exists in 2 forms: cysts, trophozoites
results in giardiasis

56
Q

Giardia lamblia cysts and trophozoites

A

cysts - intermittent on stool microscopy

trophozoites - diarrhoea specimen, duodenal biopsy or “string test” - gelatin capsule on absorbent string, swallowed and withdrawn

57
Q

Giardia lamblia treatment

A

metrondiazole

58
Q

cryptosporidium parvum

A

protozoa

2 forms: oocysts, trophozoites

water treatment relies on filtration

leads to cryptosporidiosis

59
Q

cryptosporidiosis clinical presentation

A

watery diarrhoea
N + V
abdominal cramps
low grade fever

60
Q

cryptosporidiosis transmission

A

ingestion of oocysts in faecally contaminated water

oocysts stool specimen seen on microscopy

61
Q

cryptosporidiosis treatment

A

no specific treatment usually required

62
Q

imported parasites

A

entamoeba histolytica

63
Q

entamoeba histolytica

A

protozoa - cyst and trophozoite forms

leads to amoebic dysentery

microscopic examination for trophozoites (symptomatic patient) - “hot stools”, cysts (asymptomatic patient)

amoebic liver abscess may be long term complication - anchovy pus, trophozoites multiply in liver cells

64
Q

treatment for entamoeba histolytica

A

trophozoites - metronidazole

cysts in intestine lumen - diloxanide furoate

65
Q

viral diarrhoea causes

A

rotavirus
adenovirus
norovirus

66
Q

rotavirus

A

viral diarrhoea in children <5y/o
vaccine now available in UK at 8 and 12wks
common in winter

67
Q

adenovirus

A

certain strains - 40/41

68
Q

diagnosis of adenovirus and rotavirus

A

rapid test - antigen detection

69
Q

norovirus

A

winter vomiting disease
diarrhoea and vomiting
common cause of outbreaks: hospital, community, cruise ships
very infectious (low infectious dose - 18 virus particles)
ward closures common - staff and pts affected
strict infection control measures needed - alcohol gel not effective, isolation

70
Q

diagnosis of norovirus

A

PCR

Y2 infection (15 decks)

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