GI Infection Flashcards
What is the difference between an endogenous organism and exogenous organism associated with GI infection?
Endogenous:
- due to alteration of organisms within the GI system due to disruption to balance of organisms
- leads to overgrowth of remaining bacteria
Exogenous
-entry of organism into the GI system from environment
What can cause alteration to gut glora?
What organisms is the gut flora made of?
Which organisms are commonly associated with the subsequent infection?
Immunosuppression/medication
Anaerobic and gram negative organisms
Anaerobes i.e. bacteriodes + clostridioides
Gram negative organisms i.e. enterobacteraeciae
Gram positive i.e. enterococcus
Fungi i.e. candida
What are the 3 main types of exogenous organisms responsible for infection?
What are the most common organisms within this types?
Bacteria
- campylobacter
- salmonella, Shigella, E coli
- vibrio
- staph enterotoxin
- clostridium perfringens
Virus
- rotavirus
- norovirus
Parasites
- giardia
- worms
What is diarrhoea?
Inflammation of the intestine leading to them not being able to absorb water from the stool
Therefore leads to water/loose type 5-7 stool which occurs 3(+) time per day
What is gastro-enteritis?
What might someone present with?
Inflammation of stomach and small intestine
Diarrhoae Vomiting Fever Abdominal pains Dehydration i.e. lossing lots of fluid
What is oesophagitis?
What causes it and who is at an increased risk?
What might someone present with?
What would you expect to see on endoscopy and histology?
How is it treated?
Infection and inflammation of the oesophagus
Caused by CMV
-immunosuppressed individuals at increased risk due to weakened immune system enabling reactivation of dormant CMV
I.e. HIV or immunosuppressant drugs or diabetes
Present:
- dysphagia
- odynophagia (painful swallow)
- nausea
- vomiting
Endoscopy= ulcers Histology= inclusion bodies (owl eye appearance which is the location of viral replication)
Tx:
-reduce immunosuppression
+/- ganciclovir (targets CMV)
What is thrush?
What causes it and who is at an increased risk?
What would you expect to see on endoscopy and histology?
How is it treated?
Thrush candidiasis is an overgrowth og candida albicans fungus
Causes:
- steroids/immunosuppression meaning immune system unable to control fungal overgrowth
- antibiotic alteration of flora
White plaques in oral cavity + oesophagus
Tx:
-antifungals= fluconazole
What are the charactertistic features of helicobacter pylori?
What can this bacteria cause?
What tests are used to identify a H pylori infection?
What can untreated H pylori lead to?
How is it treated?
Gram negative rod bacteria
- helical shape penetrates mucosa to avoid acid
- flagella used to motility
- converts urea to ammonia and bicarb using urease enzyme to neutralised stomach acid
Associated with stomach + duodenum ulcers
Urea breath test
-labelled carbon enters stomach in carbonate form where H pylori will convert to CO2 i.e. labelled C can be detected in CO2
Rapid urease test (CLO)
- sample taken on endoscopy and placed on CLO
- change of colour from yellow -> pink == POSITIVE
Untreated:
- stomach cancer
- gastric MALT lymphoma
Treatment= TRIPLE THERAPY for 1 week
- PPI
- clarithromycin
- amoxicillin or metronidazole
What are the key points in a diarrhoea history?
Nature of stool:
-bloody or watery?
Timeline
-when did it start and how long/often since then
Food
Travel
Acute or chronic
How does diarrhoae associate with small bowel differ from that associated with large bowel?
Small bowel
- watery diarrhoae
- caused by enterotoxin i.e. toxins produced by bacteria
Large bowel
- bloody diarrhoae (dysentery)
- caused by direct damage to musosa
What are common infectious causes of watery diarrhoae?
Enterotoxin produced by:
- staph aureus
- clostridium perfringens
- clostridium difficile
- bacillus cereus
- vibrio cholera
What are the common infectious causes of dysentery?
Salmonella
Shigella
Campylobacter
E coli
I.e. gram negative bacilli
Where does staph aureus bacteria live?
How can someone become infected and get diarrhoea?
How might someone present if they had diarrhoea associated with staph aureus infection?
Lives on skin and can be transfered to food
- bacteria multiple on good and produce enterotoxins
- bacteria are killed when food cooked but the enterotoxins survive
Rapid onset of symptoms i.e. 1-6hrs Resolves within day Vomiting Fever Abdo pain
How might someone become infected with clostridium perfringens?
How does the toxin production differ from staph aureus infection and how does this influence the presentation?
What symptoms might someone present with?
Gram positive bacilli which forms spores in food i.e. associated with bulk cooking or when food being left out for long time at inadequate temperatures
Toxins only produced once ingested
- leads to symptoms presenting slightly later i.e. 18-24hrs after (resolves in 1 day)
- no vomiting as toxin only produced once in GIT
Explosive diarrhoea
Cramping
Abdo pain
Ab
Why does a C diff infection occur?
What will someone typically present with?
What complications can occur?
Why does a patient with C diff need to be isolated?
How is C diff treated?
Alteration of colon gut flora leading to overgrowth of C diff
- broad spectrum antibiotics
- PPI= due to changing acidity of stomach
Foul smelling diarrhoea
Fever
Dehydration
Shock= due to toxins produced
Complications occur due to the toxins produced:
- pseudomembranous colitis= yellow plaques
- toxic megacolon= haustra lost on abdo XR
- bowel perforation
C diff spore forming bacteria can survive extreme conditions so need to wait for infectious period to pass to limit the spread
TX: Abx -MILD= metronidazole (IV or oral) -MODERATE-SEVERE= vancomycin (oral or rectal as IV doesn’t reach the gut) -RECURRENT= fidaxomycin Faecal transplant (last resort)
How could someone be infected with bacillus cereus?
What 2 types of toxin are produced and what symptoms are they associated with?
Associated with rice that has not been cooked at high enough temperature to kill spores and then left at room temperatire where spores germinate and produce toxins
Emetic= vomiting w/i 1-5 hrs Diarrhoeal= diarrhoea w/i 8-16 hrs
How would someone become infected with vibrio cholera + what is the route of transmission?
What is the incubation period?
What might someone present with and what is the underlying disease mechanism?
How are these patients managed?
Drinking contaminated water
I.e. faeco-oral transmission between people
Has 1-5 day incubation period
Watery diarrhoea= characteristic “Rice-water” stool
Mech:
-opens CFTR channel
-chloride secreted into gut lumen-> sodium + water follow i.e. water lost excessively into the gut lumen
Eg up to 20 LITRES
Need to rehydrates ASAP i.e. replace fluid AND electrolytes
Ciprofloxacin
How might someone become infected with salmonella enteritidis?
When will they present with symptoms and what will they be?
What is the management?
Undercooked meat
12-36hrs post-exposure and will present with bloody diarrhoea and abdo pains due to mucosal damage
Nothing- self-limiting condition which will resolve by self in 2-7 days
How does salmonella typhi differ from salmonella enteritidis?
How would someone with salmonella typhi present?
How is it treated?
Causes enteric fever rather than gastro-enteritis
Infects peyers patches and leads to fever signs rather than classic gut infection signs
Fever Myalgia Abdo pain Rash 1/3rd= constipation + 1/3rd= diarrhoea + 1/3rd= no bowel change
Azithromycin/ceftriaxone/meropenem
How would someone become infected with Shigella?
What might they present with?
What complications can occur with shigella infection?
Ingestion of water/food which has been contimated with faeces of infected person
Symptoms w/i 24hrs Tenesmus Blood diarrhoea Abdo pains Colonic perforation
Reactive arthritis + conjunctivits
Haemolytic uraemic syndrome i.e. due to RBC become fragile and prone to haemolysis
How might someone become infected with campylobacter jejuni? How long is the incubation period? What would someone present with? How is it managed? What can occur as complications?
Undercooked chicken
Unpasteurised milk
Contaminated water i.e. ice water when abroad
2-3 days
Dysentry
Self-limiting illness which should clear self
Can use macrolides or quinolone if infection persistant
Guillain Barre Syndrome
Reactive arthritis
What are the different antigens associated with Ecoli and what is the significance of this?
How would somone with E coli present and when would the symptoms present?
What are the different types of Ecoli?
Which type should you not give antibiotics to and why?
O K H antigens which can enable different serotypes of e coli
Watery stool/dysentry (depends on serotype)
Present 3-4 days after exposure
Pathogenic= watery (childhood) Toxigenic= watery (travellers diarrhoea) Invasive= bloody Haemorrhagic= bloody -avoid antibiotics because can lead to increased toxin release and make the outcome worse
What are the 4 main viruses associated with diarrhoea?
What is the general management of all of them?
Rotavirus
Norovirus
Adenovirus (children)
Enterovirus (children)
Management:
- supportive treatment
- wash hands regualrly
- isolate patients to avoid outbreak
How would the diarrhoea history of someone suffering from parasitic infection differ from bacterial or viral?
What are the 3 examples of parasitic infections which can cause diarrhoea?
Much longer history of diarrhoea which has lead to weight loss and malabsorption of nutrients
Giardia
-causes flattening of villi and lactose intolerance
I.e. causes coeliac type picture
Worms
-itching around anus + worms in stools
Schistosomiasis
- associated with swimming in fresh water i.e. lake malawi
- presents with abdo pain and blood in stool
What investigations should be done when someone is presenting with diarrhoea?
Stool MC&S i.e. microscopy/culture/sensitivity
C diff antigen testing
Test for ovas/cysts/parasites if travel history fits
Viral PCR if suspecting outbreal
Blood cultures i.e. looking for disseminated infection where gram -ve bac has entered blood
