gastroenteritis

Question 1

definition of gastroenteritis

Answer 1

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

manifested by nausea, vomiting, diarrhoea and abdominal discomfort

Question 2

types of aetiology of gastroenteritis

Answer 2

virus

bacteria

protazoa

toxins contained in contaminated food or water

Question 3

viruses causing gastroenteritis

Answer 3

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

Question 4

bacteria causing gastroenteritis

Answer 4

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

Question 5

protazoal causes of gastroenteritis

Answer 5

entamoeba histolytica

cryptosporidium parvum

giardia lamblia

cyclospora cayetanensis

trichinella

trichuriasis

intestinal flukes

Question 6

toxins that cause gastroenteritis

Answer 6

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

Question 7

commonly contaminated food causing gastroenteritis

Answer 7

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

Question 8

non-inflammatory mechanisms of gastroenteritis

Answer 8

V cholerae, enterotoxigenic e coli

produce enterotoxins that cause enterocytes to secrete water and electrolytes

Question 9

inflammatory mechanism of gastroenteritis

Answer 9

shigella, enteroinvasive E coli

release cytotoxins and invade and damage epithelium

with greater invasion and bacteraemia in the case of salmonella typhi

Question 10

epidemiology of gastroenteritis

Answer 10

common

under reported

serious cause of morbidity and mortality in the developing world

Question 11

sx of gastroenteritis

Answer 11

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

Question 12

signs of gastroenteritis

Answer 12

diffuse abod tenderness

abdo distension

increased bowel sounds

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

Question 13

investigations for gastroenteritis

Answer 13

• 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

Question 14

management of gastroenteritis

Answer 14

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

Question 15

complications of gastroenteritis

Answer 15

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

Question 16

prognosis of gastroenteritis

Answer 16

generally good

majority of conditions are self limiting

Question 17

different definitions of diarrhoea

Answer 17

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

Question 18

causative organisms of diarrhoea w/o blood ie enteritis

Answer 18

norovirus

rotavirus

astrpovirus

enteric adenovirus

enterotoxigenic E coli

enteropathogenic E coli

toxin producing staph aureus

cholera

clostridium perfringens

giardia

cyrptosporidium

cyclospora cayetaenensis

Question 19

causative organisms of diarrhoea with blood ie dysentry

Answer 19

shigellosis - bacillary dysentery

enterohaemorrhagic E colu

campylobacter enterocolitis

c diff

yersinia enterocolitis

entamoebic histolytica (amoebic dysentery)

trichuriasis (whipworm0

CMV

Question 20

summarise traveller’s diarrhoea

Answer 20

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

Question 21

summarise norovirus

Answer 21

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

Question 22

summarise rotavirus

Answer 22

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

Question 23

enterotoxigenic E coli

Answer 23

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

Question 24

clostridium perfringes (type A)

Answer 24

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

Question 25

cholera

Answer 25

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

Question 26

shigella (sonnei, flexneri, dysenteriae, boydii)

Answer 26

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

Question 27

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

Answer 27

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

Question 28

campylobacter

Answer 28

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

Question 29

salmonella enterocolitis (non-typhoidal)

Answer 29

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

Question 30

yersinia enterocolitica

Answer 30

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

Question 31

giardiasis

Answer 31

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%

Question 32

cryptosporidium

Answer 32

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

Question 33

amaebiasis

Answer 33

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

Question 34

cyclospora

Answer 34

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

Question 35

nematodes

Answer 35

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

Question 36

taeniasis (tapeworm)

Answer 36

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

Question 37

thyphoid fever mx

Answer 37

Third-generation cephalosporins. or quinolones and chloramphenicol. Notifiable disease

Question 38

summarise C difficile

Answer 38

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

Question 39

mx of c diff

Answer 39

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

Question 40

staphylococcus aureus

Answer 40

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

Question 41

clues from Hx of pathogens causing gastroenteritis

Answer 41

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