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Yr 3 Infection > gastroenteritis > Flashcards

gastroenteritis Flashcards

1
Q

definition of gastroenteritis

A

acute inflammation of lining of the GI tract due to enteric infection

manifested by nausea, vomiting, diarrhoea and abdominal discomfort

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2
Q

types of aetiology of gastroenteritis

A

virus

bacteria

protazoa

toxins contained in contaminated food or water

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3
Q

viruses causing gastroenteritis

A
  • rotavirus
  • adenovirus
  • astrovirus
  • clacvirus
  • norwalk virus
  • small round structured virus
  • norovirus
  • sapovirus
  • cmv
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4
Q

bacteria causing gastroenteritis

A
  • campylobacter jejuni
  • E coli - particularly 0157
  • salmonella
  • shigella
  • vibro cholerae
  • listeria
  • yersinia enterocolitica
  • staph aureus
  • clostridium perfringes
  • yersinia entercolitica
  • bacillus cereus
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5
Q

protazoal causes of gastroenteritis

A

entamoeba histolytica

cryptosporidium parvum

giardia lamblia

cyclospora cayetanensis

trichinella

trichuriasis

intestinal flukes

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6
Q

toxins that cause gastroenteritis

A

from staphylococcus aureus, clostridium botulinum, clostridium perfringens, bacillus cereus, mushrooms, heavy metals, seafood

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7
Q

commonly contaminated food causing gastroenteritis

A

improperly cooked meat - s aureus, c perfringens

old rice - B cereus, S aureus

eggs and poultry - salmonella

milk and cheese - campylobacter, listeria

canned food - botulinism

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8
Q

non-inflammatory mechanisms of gastroenteritis

A

V cholerae, enterotoxigenic e coli

produce enterotoxins that cause enterocytes to secrete water and electrolytes

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9
Q

inflammatory mechanism of gastroenteritis

A

shigella, enteroinvasive E coli

release cytotoxins and invade and damage epithelium

with greater invasion and bacteraemia in the case of salmonella typhi

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10
Q

epidemiology of gastroenteritis

A

common

under reported

serious cause of morbidity and mortality in the developing world

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11
Q

sx of gastroenteritis

A

sudden onset nausea, vomiting and anorexia

diarrhoea - bloody or watery

abdo pain/dyscomfort

fever and malaise

enquire about recent travel, AB use and recent food intake - how cooked, source and whether anyone else is ill

time of onset - toxins = early ie 1-24hr. Bacterial/viral/protazoal 12hr or later

effect of toxin:

  • botulinism = paralysis
  • mushrooms = fits, renal or liver failure
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12
Q

signs of gastroenteritis

A

diffuse abod tenderness

abdo distension

increased bowel sounds

if severe - pyrexia, dehydration, hypotension and peripheral shut down

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13
Q

investigations for gastroenteritis

A
  • blood
    • FBC
    • blood culture - help identify bacteraemia
    • UE - dehydration
  • stool
    • faecal microscopy for polymorphs, parasites, oocusts, culture, electron microscopy (used to dx viral infections)
    • analysis for toxins, particularly for pseudomembranous colitis (C diff toxin)
  • AXR or US
    • exclude other causes of abdo pain
  • sigmoidoscopy
    • often unnecessary unless IBD needs to be excluded
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14
Q

management of gastroenteritis

A

bed rest, fluid and electrolyte replacement with oral rehydration soln (containing glucose and salt)

IV rehydration in severe vomiting

most infections are self limiting

AB treatment only needed if severe or the infective agent has been identified eg cuprofloxacin against salmonella, shigella, campylobacter

thyphoid fever management

boulinism - botulinum antitoxin IM and manage in ITU

public health - often a notifyable disease, educate on basic hygeine and cooking

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15
Q

complications of gastroenteritis

A

dehydration

electrolyte imbalance

prerenal failure

secondary lactose intolerance - particualry in infants

sepsis and shock - particularly salmonella and shigella

haemolytic uraemic syndrome - associated with toxins from E coli 0157

Guillian-Barre syndrome may occur weeks after recovery from campylobacter gastroenteritis

botulinism - resp muscle weakness or paralysis

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16
Q

prognosis of gastroenteritis

A

generally good

majority of conditions are self limiting

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17
Q

different definitions of diarrhoea

A

acute diarrhoea >= episodes partially formed or watery stool/day <14days

dystentry - infectious gastroenteritis with bloody diarrhoea

persistent diarrhoea - acutely starting diarrhoea lasting >14d

traveller’s diarrhoea - starting during or shortly after foreign travel

food poisening - disease (infection/toxin) caysed by consumption of food/water - notifyable disease

18
Q

causative organisms of diarrhoea w/o blood ie enteritis

A

norovirus

rotavirus

astrpovirus

enteric adenovirus

enterotoxigenic E coli

enteropathogenic E coli

toxin producing staph aureus

cholera

clostridium perfringens

giardia

cyrptosporidium

cyclospora cayetaenensis

19
Q

causative organisms of diarrhoea with blood ie dysentry

A

shigellosis - bacillary dysentery

enterohaemorrhagic E colu

campylobacter enterocolitis

c diff

yersinia enterocolitis

entamoebic histolytica (amoebic dysentery)

trichuriasis (whipworm0

CMV

20
Q

summarise traveller’s diarrhoea

A

affectes 20-60% travellers

high risk areas: south asia, central and south america, africa

major cause - enterotoxigenic E coli

prevention - boil water, cook thoroughly, peel fruit and veg. Avoid ice, salads adn shellfish. Drink with a straw. Hand wash with soap

Sx - during 1st week of travel

  • enterotoxigenic E coli = watery diarrhoea, preceded by cramps and nausea
  • giardia lamblia = upper GI symptoms eg bloating, belching
  • campylobacter jejuni and shigella = colitic symptoms, urgency, cramps

Rx

  • oral rehydration - clear fluid or oral rehydration salts
  • antimobility ageents eg loperamide, bismuth subsalicyclates - avoid if severe pain or bloody diarrhoea as may indicate invasive colitis
  • AB - not usually indicated - considered if rapid cessation of diarrhoea needed and/or limited access to sanitation or healthcare

AB prophylaxis

  • not recommended - severe disease is rare and risk of c diff
  • consider in immunosuppressed, GI pathology or increased risk of dehydration (sickle, CKD)

persistant diarrhoea

  • investigate if >14d or dysentry
  • FBC, UE, LFT, CRP, ESR, stool microscopy for ova, cysts, parasites
  • molecular testing for pre-defined microbes
  • ddx of persistant diarrhoea = giardia, entamoeba histolytica, shigella
  • post infectious OBS is a dx of exclusion
21
Q

summarise norovirus

A

sigle stranded RNA virus

highly infectious

transmission - contact with infected people, env, food (approx 10%)

most common cause of infectious GI disease (approx 600000 cases in eng/yr)

Sx - 12-48hr after exposure, lasting 24-72hr. Acute vom, watery diarrhoea, cramps, nausea

virus shed in stool even if asymptomatic

numerous genotypes and unknown longevity of immunity therefore repeat infection happens

Ix - clinical, stool sample reverse transcriptase PCR

Rx - supportive, anti-motility agents, usually self limiting

22
Q

summarise rotavirus

A

double strand RNA virus

wheel like appearance on EM

commonest cause of gastroenteritis in children

Sx - incubation 2d, watery diarrhoea and vom for 3-8d, fever, abdo pain

Ix - clinical, ag in stool

Rx - supportive

routine vaccine in UK

virus shed in stool post vaccine = careful hygiene if immunocomprimised and changing nappies

live vaccine therefore delay vaccination if in utero biologic agents with active transfer across the placenta eg infliximab, adalimumab

23
Q

enterotoxigenic E coli

A

gram -ve anaerobe

disease due to heat stable or heat-labile toxin which stimulates NaVL na dwater efflux into gut lumen

20% of all infective diarrhoea, 80% of traveller’s diarrhoea

sx - incubation of 1-3d, watery diarrhoea, cramps, lasts 3-4d

dx - clinical, stool culture to identify toxin

Rx - supportive

24
Q

clostridium perfringes (type A)

A

gram +ve anaerobe

produces enterotoxin

spores survive cookung and germinate during unrefriginated storage

2-30 outbreaks/yr in the UK

Sx - sudden onset diarrhoea, cramps, <24hr

Ix - stool toxin, quantification of faecal bacteria

Rx - supportive

B toxin of C perfringens type C can cause necrotozing enteritis with fuliment disease, pain, bloody diarrhoea, septic shock

B toxin is sensitive to trypsin proteolysis so increased risk with trypsin inhibition by sweet potatoes, ascaris infection therefore occurs in New Guinae (pigbel), central/south america, south east asia, china

25
Q

cholera

A

gram -ve, aerobic comma shaped flagellated motile vibrating/swarming rod

found in faecally contaminated water

serovars 01 and 0139 cause disease

approx 190000 cases in 2014

sx - incubation 2h-5d, approx 75% asymptomatic but shed bacteria, profuse (1L/hr) diarrhoea (rice-water stool), vomiting, dehydration, metabolic acidosis, circulatory collapse, death

dx - clinical - death due to watery diarrhoea = dehydration age >5 or any watery diarrhoea >5 during known epidemic. Identification of serovars 01 or 0139 in stool. Rapid dipstick testing available but culture confirmation is recommended

Rx - oral rehydration salts, safe water, adults might need 1L/hr initially - offer 100ml/5min. NG if vom. IV fluids if severly dehydrated: Ringer’s lactate or 0.9% saline plus ORS (beware low K+) up to 200mL/kg in first 24h. Antibiotics in severe dehydration to reduce diarrhoea - doxicycline or tetracycline

zinc shortens illness in children

prevention - clean water, oral cholera vaccines

26
Q

shigella (sonnei, flexneri, dysenteriae, boydii)

A

gram -ve anaerobe

sx - wateryu or bloody diarrhoea, pain, tenesmus, fever 1-2days after exposure

lasts 5-7days - more in MSM

complications - bacteraemia, reactive arthritis, HUS

dx - stool culture, PCR.enzyme immunoassay

Rx - supportive. Green bananas (more short chain fatty acids in colon), zinc if <6yrs, vit A. AB if systemically unwell/immunocomp

avoid anti-diarrhoeal - risk of toxic dilatation

27
Q

enterohaemorrhagic/shiga-toxin producing E coli (STEC) eg O157:H7

A

gram -ve anaerobe

produces veratoxins which are shiga like due to similarity with shigella dysentriae

sx - incubation 3-8d, diarrhoea, haemorrhagic colitis. HUS in up to 10%

Dx - stool culture. PCR/enzyme immunoassay for Shiga-toxin

Rx - supportive. NO AB - increase risk of HUS

28
Q

campylobacter

A

gram -ve spiral shaped rod

Sx - incubation 1-10d (usually 2-5d). bloody diarrhoea, pain, fever, headache

complications - bacteraemia, hepatitis, pancreatitis, miscarriage, reactive arthritis, Guillain-Barre

dx - stool culture/ PCR/enzyme immunoassay

Rx - supportive, AB only in invasive cases

29
Q

salmonella enterocolitis (non-typhoidal)

A

gram -ve, anaerobic motile bacilli

presentation - diarrhoea, cramps, fever, usually with 12-36hr of exposure

invasive infection (<10%) can cause bacteraemia/sepsis, meningitis osteomyelitis, septic arthritis

Dx - stool culture, PCR

Rx - supportive

consider AB in sever/extra-intestinal disease according to local sensitivities

30
Q

yersinia enterocolitica

A

gram -ve rod

presentation - incubation 4-7d. Diarrhoea, fever, pain (may mimic appendicitis) vomiting. May last 1-3wk. erythema dodosum, reactive arthritis

dx - stool culture, agglutination titres

Rx - AB in severe disease

31
Q

giardiasis

A

giardia lamblia is a flagellate protozoan

faecal-oral spread from infected drinking water/food/fomites

Sx - asymptomatic, incubation 1-3wk, diarrhoea, flatulance, bloating, pain, malabsorption. lasts 2-6wk. Most common dx if persistent traveller’s diarrhoea

dx - stool microscopy for cysts and trophozoites. Intermittent shedding so multiple samples (>3) may increase sensitivity. faecal immunoassay. PCR for dx/subtype. duodenal fluid aspirate analysis

rx - hygiene to prevent transmission. Metronidazole (treatment failure in up to 20%), tinidazole (single dose), albendazole (less SE, simultaneous treatment of other parasites)

lactulose intolerance develops in 20-40%

32
Q

cryptosporidium

A

apicomplexan protozoan

ingestion of oocytes in infected water

asymptomatic or self-limiting diarrhoea in immunocompetent hosts

chronic/severe diarrhoea with immunosuppression - HIV, transplantation, hypogammaglobulinaemia, immunosuppressive therapy

33
Q

amaebiasis

A

protazoan entamoeba haemolutica

10% worlds population, mortality 100000/yr

faecal oral spread

boil water to destroy cysts

sx:

  • asymptomatic passaghe of cysts in 90% - luminal amoebiasis
  • intestinal amoebiasis - dysentery (often insidious onset/relapsing), pain, colitis, appendicitis, toxic megacolon. Amoeboma - inflammatory abdominal mass, usually caecal/RIF +- obstruction
  • extra-intestinal (invasive) disease - amoebic liver abscess in 1%. single mass containing anchovy-sauce pus. High swinging fever, RUQ pain/tenderness. LFT normal or high - cholestatic. 50% have no history of amoebic dysentry. Also peritonitis (rupture of colonic abscess), pleuropulmonary abscess cutaneous/genital lesions

dx

  • microscopy of stool (cysts and trophozoites), aspirate or biopsy
  • enzyme immunoassay - ag detection as adjunct to microscopy, Ab detection in extra-intestinal disease
  • PCR can distinguish E histolytica from morphologically identical but non-invasive E dispar

Rx

  • metronidazole/tinidazole for amoebic dysentry and invasive disease
  • diloxanide furoate - luminal agent 10d course to destroy gut cysts, given in asymptomatic gut carriers adn symptomatic disease, in addition to other treatment.
  • abscess may require (image guided) drainage
34
Q

cyclospora

A

coccidean protazoan - cyclospora cayetanesis

approx 50 imported cases a yr

sx - flu like prodrome, watery diarrhoea, weight loss, marked fatigue, low grade fever in 35%. self limiting in 7-9wks

dx - autoflurescent oocytes in stool - appear blue-green under UV flurescence. PCR

treatment - co-trimoxazole

35
Q

nematodes

A

roundworm - ascaris lumbricoides approx 1 billion affected. Tricinella spiralis - contaminated meat source

whipworm - truchuris trichiura, 600-800 million affected

hookworm - nector americanus, ancyclostoma duodenale approx 700 million affected

threadworm - strongloides stercoralis, 30-100million affected

one of the most common infections in the world - affects the poor and deprived

parasites live in intestines, producing 1000s of egg/day in faeces

humans infected by eggs (ascariasis, trichinosis) or larvae (ancylostoma) in contaminated food or via direct penetration of the skin - kookworm, strongyloides

sx - diarrhoea, abdo pain, blood/protein loss, impaired growth/cognitive development. pruritis/urticaria if migration involves skin (strongyloides). Lung invasion (ascarias, hookworm, strongyloides) –> loeffler-like syndrome (cough, SOB, wheeze, haemoptysis, consolidation, eosinophilia). other tissue invasion (trichinosis) - myalgia, conjunctivitis, photophobia, meningitis, encephalitis, neuropathy

dx - clinical, eggs in stool, eosinophilia

rx - anthelmintic drugs

36
Q

taeniasis (tapeworm)

A

includes taenia solim (pork, 2-8m, 50000 eggs/worm) taemia saginata (beef 4-12m, 100000 eggs/worm), taemia asiatica (asian, 4-8m, millions of eggs)

sx - no or mild GI symptoms, tapeworm segments through anus/in faeces

dx - eggs/proglottids in faeces

rx - praxiquantel, niclosamide

37
Q

thyphoid fever mx

A

Third-generation cephalosporins.

or quinolones and chloramphenicol.

Notifiable disease

38
Q

summarise C difficile

A

gram +ve anaerobic bacillus

most common healthcare associated pathogen

part of flora in some people

coverts to vegetative (growth) state - production of enterotoxins A and B = colitis

happens when inhibition by competing flora is lost because of AB - consider in all diarrhoea with AB esp if neutrophilia

watery diarrhoea, mild -> fulminant colitis

ileus, toxic megacolon

ix - immunoassay for glutamate dehudrogenase (common ag), detection of toxin (toxin immunoassay, toxic gene nucleic acid amplification - distinguish infection from carrier

39
Q

mx of c diff

A

SIGHT

  • suspect
  • isolate with 2hr
  • gloves and aprons
  • hand wash with soap
  • test immediately

mild - metronidazole

severe (WCC >15x10(9)/L or AKI, or colitis, or >38.5 degrees) - vancomycin of fidaxomicin

non-responders - high dose vancomycin + IV metronidazole, fidaxomicin, IV immunoglobulin

recurrence - weaning vancomycin, fidaxomicin, faecal transplantation

40
Q

staphylococcus aureus

A

coagulase +ve

toxin release = disease distant from infection - preformed toxin in food = sudden D and V

dx - +ve culture from relevant site

Mx - sepsis management, supportive

41
Q

clues from Hx of pathogens causing gastroenteritis

A

C. Diff: Use of antibiotics, antiperistaltic drugs

Staph aureus: food, 1-6 hours after eating, short lived

Vibrio cholera: rice water diarrhoea, poor sanitation, shock

E. Coli: leafy vegetables

Bacillus cereus: reheated rice, can cause cerebral abscess

Salmonella: eggs, poultry may present with constipation, multiplies in Payer’s patches of the intestine

Campylobacter: uncooked poultry

Haemorrhagic E.coli: leafy vegetables - Bloody diarrhoea followed by haemolytic uraemic syndrome

Entamobea histolytica: poor sanitation, tropical places, MSM

Shigella: person-to-person contact, poor sanitation, MSM

Salmonella: eggs

Yr 3 Infection (25 decks)

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