GI16 - Gastrointestinal Infections Flashcards
5 general features of gastrointestinal infections
Organisms
Transmission
Symptoms
Investigations
Treatment
1.) Organisms - can be bacteria, viruses or parasites
2.) Transmission - faeco-oral
- often through food and water supplies
3.) Symptoms - generally cause non-bloody diarrhoea
- organisms causing bloody diarrhoea are shigella and STEC (E Coli O157), Clostrodium difficile, entamoeba histolytica, campylobacter
- fever, malaise, nausea/vomiting, abdominal cramps
4.) Investigations - stool culture mainly
- can also do PCR, microscopy and enzyme immunoassay
5.) Treatment - self-limiting if immunocompetent
- immunosuppressed individuals may be need antibiotics due to more severe symptoms
3 features of enterotoxigenic E.coli (ETEC)
Transmission
Pili
Diarrhoea
1.) Transmission - food and water contaminated by human waste (faeco-oral) or from person to person
- most common cause of traveller’s diarrhoea
2.) Pili - allows ETEC to bind to SI mucosa to colonise it
3.) Secretory Diarrhoea - enterotoxins (heat-stable (ST) and heat-labile (LT) toxin) causes oversecretion of Cl- into the gut lumen and prevents absorption of Na+ ions
- this draws water into gut lumen –> watery diarrhoea
4 features of E.Coli O157 (STEC)
Mechanism
Diarrhoea
Haemolytic Uraemic Syndrome
Treatment
1.) Mechanism - A1 fragment of toxin inactivates ribosomses thereby inhibiting protein synthesis
2.) Bloody Diarrhoea - causes painful, bloody diarrhoea
- often there is no fever present
3.) Haemolytic Uraemic Syndrome
- acute kidney injury (AKI), haemolytic anaemia and thrombocytopenia
4.) Treatment - worsened by antibiotics
- supportive treatment only (fluids, painkillers etc.)
5 features of salmonella (non-typhoidal) infections
2 Types of Salmonella
Transmission
Symptoms x4
Complications x5
Treatment
1.) 2 Types of Salmonella - typhoidal and non-typhoidal
- typhoidal: causes enteric fever (S. typhi, S.paratyphi)
- non-typhoidal: causes gastroenteritis (S.enteritidis, S.virchow)
2.) Tranmission - food, faeco-oral, animals
3.) Symptoms
- fever, abdominal cramps
- non-bloody diarrhoea, nausea/vomiting,
4.) Complications
- bacteraemia, endovascular infections, abscesses
- osteomyelitis and septic arthritis
5.) Treatment - usually self-limiting (2-3 days)
- if not, ceftriaxone or azithromycin
5 features of Campylobacter infections
Transmission
Incubation Period
Symptoms x5
Complications x2
Treatment
1.) Transmission - faeco-oral in meat products or water
- common in undercooked poultry so rise in BBQs
2.) Incubation Period - 1-7 days
- ‘food infection’ so requires time to colonise intestines
3.) Symptoms - diarrhoea (can be bloody)
- abdominal cramping, fever, malaise, bacteriaemia
4.) Complications
- reactive arthritis
- Guillain-Barre Syndrome (GBS): immune system attacks peripheral spinal nerves
5.) Treatment - usually self-limiting unless in immunocompromised, elderly or severe infections, treat with:
- 1°macrolides (clarithromycin) or 2°fluoroquinolones (ciprofloxacin)
6 features of shigella infections
Disease
Transmission
Symptoms x5
Intestinal Complications x5
Systemic Complications x4
Treatment
1.) Disease - shigellosis (bacillary dysentery)
- invade the colon and destroy the mucosa
2.) Transmission - person to person (source is stools)
- very small dose (10-100) required to cause infection
3.) Symptoms - low volume bloody diarrhoea with mucus
- fever, tenesmus, abdominal cramping
- nausea/vomiting usually absent
4.) Intestinal Complications
- perforation, obstruction, toxic megacolon
- proctitis (inner rectum inflammation), rectal prolapse
5.) Systemic Complications
- bacteriaemia, seizures in children, reactive arthritis, haemolytic uraemic syndrome
6.) Treatment - usually self limiting
- if severe: ceftriaxone, azithromycin
5 features of rotavirus infections
Demographic
Mechanism
Symptoms
Complications
Treatment
1.) Demographic - important cause of gastroenteritis in young children, responsible for half the incidents of severe diarrhoea in under 2s
2.) Mechanism - binds to epithelia in the SI and can survive the acidic conditions of the stomach
- interupts villi, reducing SA for absorption
- also affects amounts of digestive enzymes produced leading to a hyperosmotic lumen –> osmotic diarrhoea
3.) Symptoms - mild to severe non bloody diarrhoea
- more severe in young children
4.) Complications (rare) - affects the brain
- seizures, encephalopathy, acute encephalitis
5.) Treatment - self limiting in uncompromised individuals
- oral vaccines given at 8 and 12 weeks old
4 features of Cryptosporidium infections
Organism
Transmission
Symptoms
Treatment
1.) Organism - intra-cellular protozoan parasite
- Cryptosporidium parvum causes human infections
2.) Transmission - faeco-oral from water supply
- associated with sporadic, water associated outbreaks
3.) Symptoms - mild diarrhoea
- in immunocompromised (AIDS), it can be severe
4.) Treamtent - self limiting within 10-14 days
- nitazoxanide given to immunocompromised
6 features of Giardia infections
Organism
Transmission x4
Mechanism
Symptoms x6
Investigations
Treatment
1.) Organism - protozoan parasite
- Giardia duedenalis
2.) Transmission - faeco-oral through food and water
- associated with sporadic or epidemic infections linked to water, food, childcare settings and international travel
- long incubation period: 1-2 weeks
3.) Mechanism - ingested parasites attach to the walls of the duodenum
4.) Symptoms - mild to severe non-bloody diarrhoea
- steatorrhoea, abdominal cramps, bloating
- symptoms can be prolonged >2 weeks
- can be asymptomatic and persist as a chronic infection leading to malabsorption and weight loss
5.) Investigations - stool analysis may be negative because the infection is in the upper GI tract
6.) Treatment - given to symptomatic patients
- metronidazole or nitazoxanide
4 features of Entamoeba histolytica infections
Mechanism
Symptoms (4 risk factors)
Complications x2
Treatment
1.) Mechanism - protozoan parasite can survive passage to the colon where they feed on colonic bacteria
- they can invade epithelial cells –> ulceration
- very long incubation period (2 weeks to years)
2.) Symptoms - often asymptomatic
- risk factors for severe disease: young age, alcoholism, malnutrition, immunocomprised states
- can cause bloody diarrhoea and abdominal pain
3.) Complications
- spreads to the liver –> ameobic liver abscess
- colitis with necrosis and perforation (mimics IBD)
4.) Treatment
- high dose metronidazole followed by intraluminal agent (paromomycin) to kill the cysts
