GI Infections Flashcards
What is the Bristol stool chart?
Diagnostic medical tool designed to classify the form of human faeces into seven categories
1+2 = constipation
3+4 = normal
5-7 = diarrhoea
What questions needs to be asked when managing diarrhoea?
Duration
Frequency
Travel
Exposure/contact history – farm animal, sewage
Co-morbidities
Chemo, transplant, immunedef
Occupation = health worker, work with young children, care-worker
In general how are GI infections managed?
History = particularly travel and exposure history
Physical exam = include hydration status
Samples = request the right test
Treat = fluids, +/- Abx
Infection prevention
What are the major bacterial causes of infective diarrhoea?
Salmonella
Campylobacter jejuni
Shigella
Enterotoxigenic E. coli
Clostridium difficile
What are the major viral causes of infective diarrhoea?
Norovirus
Rotavirus
Adenovirus
What are the major causes of parasitic infective diarrhoea?
Cryptosporidium
Giardia
Entamoeba
Cyclospora cayetanensis
How is a stool sample cultured?
On selective agar = enables particular MO to grow
Stool contain huge number of natural flora
How does camplylobacter appear on gram stain?
Gram -ve
‘Seagull appearance’ = spirochete
How is campylobacter transmitted?
Food
Water
Direct contact with animals/animal products
Describe the symptoms seen in a campylobacter infection
Abdominal pain, cramps
Diarrhoea (may be absent or bloody)
Nausea
Prodromal symptoms (fever, rigors, aches, dizziness)
Colitis
May mimic appendicitis
Outline the acute complications of campylobacter
Cholecystitis
Peritonitis
Rash
Septic pseudoaneuysm
Pericarditis and myocarditis
Focal extraintestinal infections.
Outline the late complications of campylobacter
Reactive arthritis
Guillain—barre syndrome – muscle paralysis may be to the extent where they need ventilation
What special stain is used when there is a travel history accompanying diarrhoea?
Modified acid-fast stain
How is a camplyobacter infection treated?
Self limiting
Abx only when severe = fluoroquinolone or macrolide (only reduced symptom length by a day = limited purpose)
What is cyclospora cayetanensis and what does it cause?
Coccidian parasite
Travellers diarrhoea
How is cyclospora cayetanensis transmitted?
Faeco-oral transmission via contaminated food/water
Describe the symptoms seen in cyclospora cayetanensis infection
Average length of illness = ~3 weeks Anorexia Nausea Flatulence Fatigue abdominal cramping watery diarrhea low-grade fever weight loss
How is cyclospora cayetanensis treated?
Fluid rehydration
Trimethoprim-sulphamethoxazole
What is a lateral flow test?
Intended to detect presence/absence Ag/Ab
What lab technique is used to identify the norovirus?
Electron microscopy
What is the most common cause of epidemic gastroenteritis?
Norovirus
How is norovirus transmitted?
Faeco-oral, person-to-person
<100 viral particles required
How is a norovirus infection treated?
Fluid rehydration
No antiviral treatment available
Describe the key features of the gut immune response to infection
Villi and underlying surface = host immune cells
Peyer patches = scattered along surface, contain T/B cells, dendritic cells (IL-6, 12), macrophage, running to mesenteric lymph node
Mucosal barrier on the ep
M cells = enables transcytosis for Ag sampling
IL-10 = anti-inflam cytokine
Outline the function of gut-associated lymphoid tissue (GALT)
Largest collection of lymphoid tissues in the body
Consisting = mesenteric lymph nodes, peyers patches
Carry out immune attacks and education of the immune system = defence against pathogens
Describe the importance of the gut microbiome and the role of commensal organisms
Helps control digestion
Controls immune system = communicates with immune cells controlling how they respond
Describe an approach to a patient presenting with traveller’s diarrhoea
Take a history = travel
Explore symptoms = nausea, fatigue, abdo cramping, watery diarrhoea, low-grad fever
Causes = giardia, entamoeba, cyclospora cayentanensis
Describe the key features of Cryptosporidium
Parasite
Symptoms = watery diarrhoea, abdo pain, nausea, vomiting
Transmission = via faeces or coughing formites
Treat = most people recover without treatment, consume fluids
How can a parasitic infection of the GI tract be diagnosed?
Enzyme immunoassay (EIA)
Faecal stool exam = 3 or more samples on separate days
Cellophane tape test = looking for eggs
Endoscopy = used when stool exams do not reveal cause
Serology = Ab or parasitic Ag
Blood smear = under a microscope
Describe the importance of infection prevention and infection control measures with regard to GI infections
Hand washing Not sharing food PPE Isolation Environmental cleaning 48hr rule
What are the causes of travelers diarrhoea?
giardia
entamoeba
cyclospora cayentanensis
