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Infectious diarrhoea Flashcards

(70 cards)

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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
investigations in a patient with gastroenteritis
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
26
differential diagnoses
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
27
treatment of gastroenteritis
oral rehydration w/ salt/sugar solution | IV saline
28
campylobacter enteritis
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
29
post-infection campylobacter sequelae
Guillain Barre syndrome | Reactive arthritis
30
salmonella gastroenteritis
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
E. coli O157
infection from contaminated meat or person-to-person spread (low inoculum) typical illness characterised by frequent bloody stools abdo pain
32
toxin produced by E. coli O157
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
what is HUS
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
how does E. coli O157 lead to HUS
toxin activated platelet activation | micro-angiopathy results
35
when are antibiotics indicated in gastroenteritis
immunocompromised pts severe sepsis or invasive infection chronic illness e.g. malignancy not indicated for healthy pt w/ non-invasive infection
36
what abx are used for campylobacter infection
macrolides | e.g. clarithromycin, azithromycin
37
what abx are used for salmonella infection
many salmonellas are still sensitive to ciprofloxacin | ceftriaxone is used for more resistant salmonellas
38
routine bacterial culture for bacterial gastroenteritis
difficult to find pathogen alongside complex normal flora selective and enrichment methods of culture necessary takes 3 days to complete all tests
39
routine bacterial culture - campylobacter
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
routine bacterial culture - salmonella
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
commonest salmonella infections in UK
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
other causative bacteria
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
which strains of Ecoli cause diarrhoea
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
occasional causes of food poisoning outbreaks
``` Staph aureus (toxin) Bacillus cereus (re-fried rice) Clostridium perfringens (toxin) ```
45
C. difficile diarrhoea
Clostridioides difficile patient usually has hx of prev abx treatment (4c abx) severity ranges from mild diarrhoea to severe colitis
46
what toxins does C difficile produce
enterotoxin and cytotoxin | inflammatory
47
how is C difficile treated
metronidazole ORAL vancomycin fidaxomicin stool transplants surgery may be required
48
C difficile infection prevention
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
what are the 4 Cs
cephalosporins co-amoxiclav clindamycin ciprofloxacin
50
management of C diff infection
stop precipitating abx (if possible) follow published treatment algorithm - oral metronidazle if no severity markers oral vancomycin is 2 or more severity markers
51
what are the severity markers
raised temp >38.5 WCC >15 acute rising creatinine suspicion of colitis/ileus/toxic megacolon
52
parasitology
protozoa and helminths diagnosis generally by microscopy send stool with request " parasites, cysts and ova" (P,C and O)
53
UK parasites
Giardia lamblia cryptosporidium parvum
54
Giardiasis
abdominal cramps bloating nausea and bouts of watery diarrhoea malabsorption and failure to thrive
55
Giardia lamblia
(aka G. duodenalis/intestinalis) protozoa contaminated water exists in 2 forms: cysts, trophozoites results in giardiasis
56
Giardia lamblia cysts and trophozoites
cysts - intermittent on stool microscopy trophozoites - diarrhoea specimen, duodenal biopsy or "string test" - gelatin capsule on absorbent string, swallowed and withdrawn
57
Giardia lamblia treatment
metrondiazole
58
cryptosporidium parvum
protozoa 2 forms: oocysts, trophozoites water treatment relies on filtration leads to cryptosporidiosis
59
cryptosporidiosis clinical presentation
watery diarrhoea N + V abdominal cramps low grade fever
60
cryptosporidiosis transmission
ingestion of oocysts in faecally contaminated water oocysts stool specimen seen on microscopy
61
cryptosporidiosis treatment
no specific treatment usually required
62
imported parasites
entamoeba histolytica
63
entamoeba histolytica
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
treatment for entamoeba histolytica
trophozoites - metronidazole | cysts in intestine lumen - diloxanide furoate
65
viral diarrhoea causes
rotavirus adenovirus norovirus
66
rotavirus
viral diarrhoea in children <5y/o vaccine now available in UK at 8 and 12wks common in winter
67
adenovirus
certain strains - 40/41
68
diagnosis of adenovirus and rotavirus
rapid test - antigen detection
69
norovirus
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
diagnosis of norovirus
PCR

Y2 infection (15 decks)

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