Infectious Diarrhoea week 3 gi block lecture

Question Answer
define diarrhoea 3 or more loose or watery stools per day
what's the pathogenic mechanisms of diarrhoea? toxin mediated – produced prior to consumption (s.aureus, b.cereus), produced after consumption (c.difficile, e.coli 0157), damage to intestinal epithelial surface, invasion across intestinal epithelial barrier
what are some non intestinal manifestations of diarrhoea? botulism (rare and potentially fatal illness caused by a toxin produced by the bacterium Clostridium botulinium), Guillain Barre (campylobacter – group of bacteria that are a common cause of food poisoning)
what's a common symptom of infectious gastroenteritis? nausea – vomiting is less common
what does a sudden onset of vomiting within 6-12 hours of food ingestion suggest? pre formed toxin – s.aureus and b.cereus. the virus norovirus can also cause vomiting
what causes large volume watery diarrhoea? what symptoms do you get and what is rare with this type? fluid and enzyme secretion, nutrient absorbing, cramps, bloating, wind, weight loss, fever and blood in stool are rare
what causes frequent small volume, painful stool diarrhoea? What's common? absorption fluid and salt, potassium excretion – fever and blood common
give some bacteria that cause diarrhoea shigella, salmonella, clostridium difficile, e.coli 0157
what viruses cause diarrhoea norovirus, sapovirus, rotavirus, adenoviruses
what parasites cause diarrhoea Giardia, Isospora, Cyclospora
what do you do with a patient with suspected diarrhoea? take a history, faecal leukocytes/occult blood, stool examination/culture, endoscopy
what sort of questions do you need to ask whilst taking a history as a guide to potential pathogen? food history, residence, onset and nature of symptoms, travel, occupation, co morbidity, recent hospitalisation/antibiotics
what might the presence of faecal leukocytes indicate? But what? a colonic or 'inflammatory' cause – BUT poor sensitivity and specificity, not used clinically
what's faecal occult blood? refers to blood in the faeces that is not visibly apparent
if there is faecal occult blood what is the most likely cause of diarrhoea? bacterial cause
what can the levels of faecal calprotectin be like in diarrhoea? can be raised but not specific for infection
what should you consider if a parasitic cause is possible? consider microscopy of ova and cysts
how can you treat diarrhoea? oral rehydration solution – small intestinal Na-glucose cotransport remains intact. can absorb water if Na and glucose are also present. If patient is vomiting they may require i.v. fluid replacement
in which situation can antibiotics worsen the outcome? if the cause is E.coli 0157:H7
why aren't antibiotics that useful in treating diarrhoea? Because it's a self limiting illness – antibiotics reduce duration of diarrhoea by about 1 day
who should get antibiotics for diarrhoea? very ill patients – sepsis or evidence bacteraemia
how long do stool cultures take for a result 48-72 hours
what's the infecting dose of campylobacter? 9000 organisms
what's campylobacter sensitive to? sensitive to stomach acidity, so beware of things that reduce stomach acidity
what does campylobacter do? attach and invade intestinal epithelial cells in small and large bowel
what's the incubation period of campylobacter 3 days (1-7days)
give the clinical features of campylobacter diarrhoea (frequent and can be high volume), blood in stool common, often severe abdominal pain, fever, nausea common/vomiting rare
antibiotics for campylobacter? high rates resistance, develop resistance on treatment
late complications of campylobacter? reactive arthritis, Gullaine-Barre
what's the infectious dose of salmonella? 10,000 organisms
what increases the risk of getting salmonella? increased risk with decreased stomach acid, increased risk with diminished gut flora
what does salmonella do to enterocytes? invasion of enterocytes with subsequent inflammatory response
give symptoms of salmonella nausea, diarrhoea, abdominal cramps, fever
how long do you get ill after ingesting salmonella? 72 hours
what secondary infections can you get from salmonella? endocarditis, osteomyelitis, mycotic aneurysm
give the pathogenesis of E.coli 0157:H7 attachment, Shiga toxin production, enterocyte death, enters systemic circulation
infectious load of E.coli 0157:H7 infectious load as little as 10 organisms, sporadic outbreaks
symptoms of E.coli 0157:H7 ? bloody diarrhoea and abdominal tenderness, fever is rare
incubation period of e.coli 0157:H7 3 to 4 days
name a severe complication of E.coli 0157:H7 infection haemolytic uraemic syndrome – systemic effect of shiga toxin
what triad does haemolytic uraemic syndrome come with acute renal failure, thrombocytopenia, microangiopathic haemolytic anaemia
what do 50% of patients with haemolytic uraemic syndrome require? dialysis
what percentage of patients infected with e.coli 0157:H7 can get haemolytic uraemic syndrome? up to 9%. happens 5-10 days after onset of diarrhoea. associated with antibiotics
how can you prevent e.coli 0157:H7 infection? strict infection control for healthcare workers, screening of contacts, appropriate butchering of meat, public health measures in outbreaks
give risk factors for clostridium difficile infection antibiotic exposure, older days (65+), PPI use, hospitalisation
give the pathogenesis of clostridium difficile decrease in colonisation resistance, colonic colonisation, toxin production
symptoms of clostridium difficile infection loose stool and colic (excessive, frequent crying in a baby that appears to be otherwise healthy), fever, leucocytosis, protein losing enteropathy
diagnosis of clostridium difficile infection: toxin detection tissue culture assay: high sensitivity, time consuming, EXPENSIVE. detect C.diff antigen plus or minus the C diff toxin
treatment of clostridium difficile associated diarrhoea stop causative antibiotics if possible (narrow spectrum), metronidazole/vancomycin, recolonize with normal flora
what's the most common cause of gastroenteritis? viral cause – norovirus most common cause of epidemics
transmission of norovirus faecal oral route, infectious dose 10-100 viruses, very stable (up to 60 degrees, bleach, alcohol gel)
seasonality of norovirus? occur in all months with peak in winter
clinical features of norovirus acute explosive diarrhoea and vomiting, 24-48hours, no lasting immunity

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