9a.) GI Infections Flashcards
Define, and describe difference between, microbiome and microbiota
- Microbiome: refers to all genomes in gut environment
- Microbioata: refers to all organisms within gut
State 5 functions of the gut microbiota
- Pathogen inhibition: act as competitors against pathogenic organisms e.g. for nutrients
- Immune protection: microbiota interact with gut lymphoid tissue; if gut senses microorganisms that shouldn’t be there immune response will occur
- Nutrient metabolism
- Drug metabolism
- Gut brain axis: thought that gut microbiota has role depression, anxiety etc…
Why can antibiotics lead to a infection?
Antibiotics can decrease gut microbiota which usually inhibit pathogens in gut
Describe how someone may present if they have a GI infection
- Diarrhoea
- Mucus/blood in stool
- Nausea
- Vomitting
- Pain
If someone presents with GI infection, what questions must you ask about their past medical history?
- Immunocompromised state
- Other GI conditions e.g. IBD
If soemone presents with GI infection what must you ask about their:
- Travel history
- Drug history
- Social history
Travel
- Where, when, how long
- Activities e.g. swimming?
- Food and drink
- Animal contact
- Travel companions & household companions…. are they ill?
Drugs
- Recent antibiotics
- Proton pump inhibitors
- Laxatives
- Immunosupressant medications
Social history
- Occupation (can help you figure out possible cause but also may have implications for returning to work)
Summarise the bristol stool chart
Should you tell microbiology if there is any travel history?
YES- so they can run approriate tests
Compare watery and inflammatory diarrhoea (generally)
Watery
- Small intestine
- Bloating/ cramping
- Large volume leading to volume depletion
Inflammatory
- Bloody diarrhoea
- Smaller volume
- Pain on opening bowels
State some conditions salmonella can cause
- Gastroenteritis
- Enteric fever
- Bacteraemia
- Osteomyelitis
- Septic arthritis
State the two broad categories salmonella can be divided into
- Typhoidal salmonella: cause enteric fever
- Non-typhoidal salmonella: causes gastroenteritis
In which patient population is osteomyelitis common when there is an infection with salmonella?
Sickle cell patients
When examining someone with GI infection, what things should you look for to determine volume status
- Mucous membranes
- Blood pressure
- Pulse
- JVP
For non-typhoidal salmonella, state:
- Gram stain
- Shape
- Transmission route
- Incubation period
- Gram -ve
- Bacilli
- Transmission: food, faecal-oral mechanisms, animals
- Incubation: 8-72 hours
What GI organ does salmonella invade?
Small intestine
State some symptoms of someone who has non-typhoidal salmonella infection in GI tract
Is it self-limiting?
- Nausea/vomitting
- Fever
- Abdominal cramping
- Non-blood diarrhoea
Yes, usualy resolves in 2-3 days
For Campylobacter, state:
- Gram stain
- Shape
- Transmission route
- Incubation period
- Gram -ve
- Helical/spiral shaped
- Faeco-oral route found in uncooked meat, untreated water and unpasteurised milk
- ~3 days (can take up to 7 days)
State symptoms of someone who has been infected with campylobacter
Is campylobacter self limiting?
- Abdominal cramping
- Diarrhoea (can be bloody or non-bloody)
- Fever
- Malaise
Yes, but can last days to weeks. Consider treatment in immunocompromised, elderly or if infection severe
State 2 complications of campylobacter
- Reactive arthritis
- Guillain-Barre syndrome (immune system attacks peripheral nerves causing parathesia and/or paralysis which starts in hands and feet and moves more central)
What is Shigellosis?
Infection of intestines (bacterial dysentry) caused by Shigella bacteria
What is bacterial dysentry?
Bacterial infection of intestines that causes severe diarrhoea with blood
For Shigella, state:
- Gram stain
- Shape
- Transmission route
- Incubation period
- Gram -ve
- Rod
- Transmission: faecal oral, food, water, person to person (usually by contaminated stools) due to low infectious dose
- Incubation: 1-7 days
State symptoms of someone who has Shigellosis
Is Shigellosis self-limiting?
- Bloody diarrhoea
- Mucus
- Abdominal cramping
- Tenesmus
NOTE: nausea & vomitting usually absent as this is infection of colon
Yes, self limiting unless host is immunocompromsied
A very small dose is all that is required to cause Shigella infection; true or false?
True; only 10-100 organisms needed
Describe how Shigella infects the GI tract (think about where in GI tract it invades and what it does)
- Invades colon
- Destroys mucosa
- Leading to blood diarrrhoea with mucus and abdo cramping
Since Shigella has very low infectious dose, and is therefore easily spread, which patient groups must we take extra considertions for?
Those who may spread it e.g.:
- Food handlers
- Health care workers
- Child care workers
State some potential systemic complications of Shigella infection
- Seizures (children)
- Reactive arthritis
- Haemolytic uraemic syndrome
For enterotoxigenic E.coli (ETEC), state:
- Gram stain
- Shape
- Transmission
- Virulence factors (2)
- Gram -ve
- Rod
- Transmission: food or water contaminated by human waste or person-to-person
- Virulence:
- Pili: bind to small intestine mucosa
- Produces enterotoxins that cause oversecretion of Cl-ions into lumen and stop absorption of Na+ drawing water into gut lumen causing watery diarrhoea
Describe how Enterotoxigenic E.Coli causes water diarrhoea
- Uses pili to bind to small intestine mucosa and then colonise on it
- Produces enterotoxins that cause oversecretion of Cl-ions into lumen and stop absorption of Na+ drawing water into gut lumen causing watery diarrhoea
State symptoms of someone infected with Shiga-toxin producing E.COli
- Bloody diarrhoea
- Abdo pain
Can cause haemolytic uraemic syndrome (non-immune mediated haemolytic anaemia, thrombocytopenia, AKI)
Why must you NOT treat Shiga toxin-producing E.Coli with antibiotics?
Makes it worse as antibiotics allow bacteria to produce more toxins
For Clostridium difficile, state:
- Gram stain
- Shape
- Tranmission
- Gram -ve
- Rod
- Can be caused by antibiotics and spread by spores (faecal oral route)
Describe how antibiotics can cause C-Diff overgrowth and state 4 antibiotics commonly associated with this
C-Diff part of normal bacterial flora, antibiotics reduce number of other bacteria allowing C-Diff to proliferate.
Antibiotics commonly associated:
- Amoxicillin
- Ampicillini
- Cephalosporins
- Clindamycin
Can C-diff still be spread to others once antibiotics, that had caused C-Diff, have stopped?
Yes because spores can persist in environment for long time
State some risk factors for devleoping a C-Diff infection
- >65
- Antibiotics
- Prolonged hospitalisation
State some potential complications of C-Diff
- Colitis
- Toxic megacolon
- Perforation
Name the two toxic products produced by C-Diff and state what each does
- Enterotoxin A: stimulates excesseive fluid secretion
- Cytotoxin B: cytotoxic causes disruption of protein syntehsis and cell cytoskeleton
Can C-Diff have different severities?
- Yes
- Simpel diarrhoea to pseudomembranous colitis (inflammation of colon due to C-Diff infection)
For norovirus, state:
- DNA or RNA
- Single or double stranded
- Enveloped or non-enveloped
- Tranmission
- RNA
- Single
- Enveloped
- Faecal-oral, direct contact
State symptoms of someone infected with norovirus
Is it self limiting?
- “Winter D & V”
- Lasts up to 48 hours
- Self-limiting
Norovirus isn’t very infectious; true or false
FALSE- highly infectious
For rotavirus, state:
- DNA or RNA
- Single or double stranded
- Enveloped or non-enveloped
- Transmission
- RNA
- Double stranded
- Non-enveloped
- Faecal-oral
Is rotavirus highly infective?
Yes
What age group is rotavirus common in?
Under 2’s (responsible for 1/2 severe diarrhoea incidents)
Describe how rotavirus causes diarrhoea
- Passes through stomach as able to survive acidic conditions
- Binds to small intestine epithelia
- Affects villi decreasing SA for absorption meaning more osmotic substances left in lumen
- Also decreases amoutn of digestive enzyems produced
- Creates hyperosmotic lumen which draws water in leading to diarrhoea
Is there a vaccine for rotavirus?
Yes
Is rotavirus self-limiting?
Yes, in an immunocompetent host
For Cryptospordium,state:
- Bacteria, virus, fungi or parasite
- Intracellular or extracellular
- Where in GI tract it can reside
- Incubation period
- Parasite
- Intracellular
- Resides in lumen
- Transmission: contaminated water (often animal faeces that has contaminated it)
State symptoms of someone infected with cryptosporidium
- Mild diarrhoea
- May be severe in immunocompromsied
What is the common cause of travellers diarrhoea?
Enterotoxigenic E.Coli
For giardia, state:
- Bacteria, virus, fungi or parasite
- Transmission
- Protozoan parasite
- Transmission: food, water, faecal oral
Where in GI tract does giarda colonise in an infection?
Duodenum
State symptoms of giarda infection
- Mild to severe diarrhoea
- Steatorrhea
- Flactulence
- Abdo cramps
- Bloating
For entamoeba histolytica, state:
- Bacteria, virus, parasite, fungi
- Incubation period
- Transmission
- Parasite
- 2 weeks to years
- Transmission: feacal contamination of food and water
State symtpoms of infection with entamoeba histolytica
What disease can an infectionwith entamoeba histolytica be mistaken for? Why is this potentially very dangerous?
- Diarrhoea (can be bloody)
- Abdo pain
- Can potentially invade the epithelial cells causing ulceration in colon
- Hence, can be mistaken colitis
- Treat UC with corticosteroids which reduce immune system and make infection worse
Where in GI tract does entamoeba histolytica usually colonise?
Colon
State 2 potential complications of infection with entamoeba histolytica
- Amoebic dysentery
- Amoebic liver disease (spread to liver and form abscess)
Describe how we can prevent spread of GI infections
- PPE
- Isolation
- Hand hygiene (NOTE: hand gel doesn’t work for killing C-Diffor Norovirus- best advice to always wash hands if GI infection)
- Clean infected room with chlorine based disinfectant after discharge
