Gastrointestinal Infections Flashcards
What is acute gastritis?
Presentation
Inflammation of the stomach presenting with epigastric pain, N+V
What is enteritis?
Presentation
Inflammation of the intestines presenting with abdominal pain + diarrhoea
What is gastroenteritis?
Presentation
Inflammation from the stomach to the intestines presenting with pain, N+V + diarrhoea
What toxins can affect the GI tract?
- Chemical
- Bacteria
- Viruses
- Protozoa
- Roundworms (nematodes)
- Tapeworm (cestodes)
- Flukes (tremtodes)
What defences does the GI system have against toxins?
- sight, smell, memory
- saliva: antibacterial enzymes
- gastric acid
- commensal bacteria
- colonic mucous
- bile in duodenum
- anaerobic environment: small bowel + colon
Benefits of gut micro biome
- outcompete harmful bacteria for nutrients
- produces antimicrobial substances
- helps develop newborn immune system
- produce certain nutrients e.g. vitamin K
What do bacteria in colon produce?
Short chain fatty acids
e.g. acetate, propionate, butyrate
Function of the SCFAs produced by the bacteria in colon
- Butyrate: energy source of coloncytes + helps regulate gut environment
- Acetate: helps reduce satiety
- propionate: reduces serum cholesterol
CHECK may not be right
What health conditions can decrease the diversity of the gut microbiome?
Obesity
Inflammatory bowel disease
What is faecal microbiota transplant?
Therapeutic procedure in which you transfer healthy donor fences into GI tract of another to restore a balanced gut microbiome.
Route of administration in faecal microbiota transplant
- nasoduodenal tubes
- upper GI endoscopy
- colonoscopy
- caecum >distributed throughout length of colon
What condition has been treated with faecal microbiota transplant effectively?
Clostridioides difficile infection
What is the criteria for selecting donors for faecal microbiota transplantation?
- 10-25 year olds
- not used antibiotics, laxatives or diet pills in last 3 months
- have no GI disease
- screen for hepatitis, HIV, inflammatory markers
What is dysbiosis?
Imbalanced gut microbiome
How can different diet choices affect gut microbiota?
- high fibre: increases health
- gluten free diet in those without coeliac disease: lowers number of key species
- sweeteners: disrupt diversity
- prebiotics: food for microbiota (good)
Name bacterial infections of the gut + their gram stain
gram negative bacilli:
- salmonella
- campylobacter
- shigella
- enterotoxigenic E. coli
gram positive
- Clostridioides difficile
Gram stain of salmonella bacteria
Gram negative bacilli
Symptoms of salmonella
- Nausea
- Vomiting
- Non bloody diarrhoea
- Fever
- Abdominal cramping
How is salmonella spread?
Ingesting contaminated food + water
Outline a salmonella infection inside the gut
- salmonella endocytosed into enterocytes
- move to submucosa > taken up by macrophages
- macrophages transfer salmonella to reticuloendothelial system
- multiply inside cells
- causes lymphoid hyperplasia + hypertrophy
- re enter gut from liver
Treatment of salmonella
Self limiting in 2-3 days
Fluids
Gram stain of campylobacter
Gram negative bacilli
S shaped
How is campylobacter spread?
Via faeco-oral route
Eating raw poultry
Drinking unpasturisied milk or untreated water
Symptoms of campylobacter infection
- fever
- abdominal cramping
- profuse diarrhoea (can be bloody)
- vomiting
Treatment of campylobacter infection
- Self limiting (few days - weeks)
- Fluid/electrolyte replacement
- antibiotics if bloody diarrhoea: clarithromycin
What infection is associated with eating poultry?
Campylobacter
(Salmonella)
Why do you get profuse diarrhoea in campylobacter infection?
Releases a cytotoxin
(Similar to cholera)
What does a shigella infection cause?
Shigellosis
Gram stain of shigella
Gram negative bacilli
How is shigella spread?
From infected stools
Person to person
Contaminated water or food
Often spread between family members
Symptoms of shigella infection
Bloody diarrhoea with mucous
Abdominal cramping
Outline a shigella infection in the gut
- endocytosed into large intestinal + rectal cells
- break out from endocytosis vesicle
- multiple inside cell where they are protected from macrophages
- mucosal abscess forms as cell dies
- causes blood diarrhoea with mucous + abdominal cramping
- shigella invade neighbouring cells
Who is shigella infection common in?
Young children
<5
Treatment of shigella infection
Self limiting
Resolves in a week
Complication of shigella
Shiga toxin can cause haemolytic uraemic syndrome
What is haemolytic uraemic syndrome?
Triad of:
- anaemia
- AKI
- thrombocytopenia
Describe enterotoxigenic E. coli
- Commensal of colon but can be a pathogen
- Gram negative bacilli
- Has flagellum
What is the common cause of travellers diarrhoea?
Enterotoxigenic E. coli
Outline enterotoxigenic E. coli infection
- ETEC adheres to enterocytes in small intestine
- enterotoxin produced
- causes hypersecretion of Cl- ions
- H2O follows
- watery diarrhoea
Why should antibiotics be avoided in E coli gastroenteritis if possible?
Shiga toxin produced can cause haemolytic uraemic syndrome
Antibiotics increased the risk of HUS
What are the gram negative bacilli which can infection the GI tract?
List from shortest to longest duration
shortest
ETEC
Salmonella
Shieglla
Campylobacter
longest
Describe Clostridioides difficle
Gram positive bacilli
Anaerobic
Spore forming
What is a major precipitating factor for Clostridioides difficle?
Broad spectrum antibiotics
Disrupts normal gut microbiota
What antibiotics are most associated with causing C difficle?
start with C:
- clindamycin
- ciprofloxacin
- cephalosporins
- carbapenems e.g. meropenem
What toxins does C difficle release?
- Toxin A: enterotoxin > excessive secretion > diarrhoea + inflammation
- Toxin B: cytotoxin > kills coloncytes
Symptoms of Clostridioides difficile
Mainly asymptomatic (during colonisation)
Diarrhoea (rarely bloody)
Abdominal cramping
Nausea
Diagnosis of C. difficile
- C. difficile antigen: glutamate dehydrogenase
- identifying A+B toxins by PCR or enzyme immunoassay
Severe rare complications of Clostridioides difficle infection
Pseudomembranous colitis
Toxic megacolon
Treatment of Clostridioides difficle infection
- removal of offending antibitoics
- fluid resuscitation
- probiotics (to replace microbiota)
- metrondiazole or vancomycin
- side room
- option of faecal microbiota transplantation for recurrent cases
What does pseudomembranous colitis look like on a colonoscopy?
Elevated yellow plaques
Most common cause of gastroenteritis
Viruses
What viruses can cause viral gastroenteritis?
Rotavirus
Norovirus
Adenovirus
What parasites cause parasitic gastroenteritis?
Cryptosporidium
Giardia lamblia
Entamoeba
What demographic does rotavirus effect?
Under 5s
Describe rotavirus
Double stranded RNA virus
Symptoms of rotavirus
- vomiting
- fever
- diarrhoea follow
Treatment of rotavirus
Manage dehydration due to fluid loss
Mechanism of rotavirus infection
- increases Cl- secretion > H2O follows > diarrhoea
- SGLT1 disruption: reduced movement of Na+/glucose into enterocyte > higher osmotic pressure in gut > H2O moves in via osmosis > diarrhoea
- brush border dysfunction: malabsorption
What demographic does norovirus effect?
Any age
(Don’t develop immunity)
Symptoms of norovirus infection
Vomiting
Water diarrhoea
Fever
Treatment of norovirus
Oral rehydration therapy
Lasts 1-3 days
What is the most common cause of non bacterial gastroenteritis?
Norovirus
Mechanism of infection of norovirus
- brush border enzyme disruption: infects small intestine + damages microvili
- delayed gastric emptying > vomiting
- anion secretion > water moves into gut > diarrhoea
Describe cryptosporidium
Protozoa - sporozoa
How is cryptosporidium infection spread?
Faecal oral route
Contaminated water with an animal faeces
Who is cryptosporidium infection common in?
Travellers
Campers
Areas of poor sanitation
Symptoms of cryptosporidium infection
Water diarrhoea
Treatment of cryptosporidium
- Self limiting
- Fluid replacement
- Anti-parasitics if at risk groups e.g AIDS
Describe gardia lamblia
Flagellated protozoa
Symptoms in gardia infection
- Mainly asymptomatic
- Symptoms more common children
- diarrhoea
- abdominal cramping
- last for up to 6 weeks
Diagnosis of giardia infection
Stool testing (NAAT or enzyme immunoassay testing)
Treatment of giardia
Fluid replacement
Antibiotics e.g. metronidazole, tinidazole
Describe the life cycle of giardia parasite
- cyst in ingested
- stomach acid/pancreatic enzyme release parasite from cyst
- multiplies in small intestine
- damages proximal small intestine
- parasite returns to cyst stage in colon
- cycle repeated
Describe entamoeba histolytica
Amoeba protozoa
Symptoms of entamoeba histolytica infection
Most asymptomatic
Bloody diarrhoea
Liver abscesses (rare)
Treatment of entamoeba histolytica
Anti protozoals
metrondiazole
Describe the infection of entamoeba histolytica
- cyst ingested
- parasite leaves cyst in colon
- trophozoites invade mucosa > bloody diarrhoea
- infection can spread to liver > liver abscess (rare)
- cysts pass out in faeces > infect others
What parasitic infection is most likely to cause persistent diarrhoea?
Gardia
What bacteria can cause haemolytic thrombocytopenia ureamia?
Shigella
Campylobacter
Post-gastroenteritis complications
- lactose intolerance
- IBS
- reactive arthritis
- Guillian-Barre syndrome
- haemolytic uraemic syndrome
