GI Microbiology Flashcards
Gastroenteritis
An illness caused by eating foods contaminated with microorganisms, toxins and poisons
Dysentery
Inflammation of the intestines, causing diarrhoea associated with blood and mucus
What microorganisms commonly cause dysentery?
Shigella
Campylobacter
Bacillus cereus key points
Short incubation
Starchy foods - rice
Vomiting
What makes bacillus cereus infection effective?
Heat resistant spores
With bacillus cereus, can you get lower GI upset?
Yes
Staph aureus key points
Foods that have been left at room temperature: meat, milk, fish
Common food is cream cake
Short incubation
Does staph aureus have a pre-formed toxin?
Yes
What are symptoms of staph aureus infection?
Vomiting
Abdominal pain
Can get lower Gi upset
What are the key points for campylobacter?
Most common cause of food poisoning
Medium incubation
Raw poultry, raw milk
What are the symptoms of campylobacter?
D&V (may be bloody)
Abdominal pain
Fever
What is there a risk of with campylobacter?
Guillain-Barre syndrome
Key points of salmonella
Medium incubation
Poultry, meat, raw eggs, raw milk
Can be transmitted from reptiles
In what way does salmonella occur?
In outbreaks
What are the symptoms of salmonella infection?
D&V - unlikely bloody
Abdominal pain
Fever
What antigen is salmonella serotypes to?
O-antigen
Shigella key points
Bloody diarrhoea
Produces toxin - type 2 is worse
Contaminated food and water
What foods are worst for shigella?
Salads, sandwiches - ones with lots of hand contact
How long is the incubation for shigella?
1-7 days
What are the symptoms of shigella infection?
Bloody diarrhoea
Vomiting
Abdominal cramps
Fever
How does the shigella toxin work?
Toxin binds to receptors on renal cells, RBCs and others
The toxin inhibits protein synthesis
Cell dies
E. Coli key points
Bloody diarrhoea
Usually undercooked beef
Produces verotoxin which can cause HUS
Do not give antibiotics - increases risk of HUS
Symptoms of E. coli
Bloody diarrhoea
May have vomiting
Abdo pain
Often no fever
How is E. coli spread?
Person-person
How does verotoxin work?
Binds to enterocytes, causing inhibition of protein synthesis
Death of cells gives verotoxin a route into the blood
Then causes death of vascular cells, causing clots to form
Verotoxin carried to kidneys, where it kills renal cells and causes renal faiure, resulting in haemolytic uraemia failure
What are the symptoms of HUS?
Bloody urine Low urine output Abdominal pain Fever Pallor Petechiae Bloody diarrhoea (may have stopped)
What age range do most cases of HUS occur in?
<16
What may precipitate HUS?
Antibiotics, anti-motility drugs and NSAIDs
What investigations are done for HUS?
FBC U&E LFT Urine samples Lactate dehydrogenase (chemical released form damaged cells)
Listeria key points
Long incubation
Pregnant women and immunocompromised
Soft cheeses, deli meats, raw milk
Listeria symptoms
Fever Stiff neck Confusion Vomiting Sometimes preceded by diarrhoea
C. diff key points
Hospitals
Broad spectrum antibiotics
Does C. diff produce a toxin?
Yes, 2: toxins A and B
What are the symptoms of C. diff?
Watery diarrhoea
Abdo pain
Fever
How are non-severe and severe C. diff treated?
Non-severe: metronidazole PO 10 days
Severe: vancomycin PO + metronidazole IV 10 days
Rotavirus key points
Children under 3, often in nurseries
Diarrhoea, not bloody
Rehydration is key treatment
What is the most common cause of diarrhoea in children under 3?
Rotavirus
Symptoms of rotavirus
Mild, watery or profuse diarrhoea
May progress from fever and vomiting
When can rotavirus be severe?
Immunocompromised children
Norovirus key points
Cruise ships, wards, nursing homes
Can be contracted from shellfish
Symptoms of norovirus
Explosive D&V
Not bloody
What are the possible investigations for gastroenteritis?
Stool culture
Stool microscopy
Stool toxin
Stool PCR
Which investigation would you do for salmonella and campylobacter?
Stool culture
Which investigation would you so for parasitic infections?
Stool microscopy
Which investigation would you do for C. diff and E. coli?
Stool toxin
Which investigation would you do for norovirus and rotavirus?
Stool PCR
In which cases would you give antibiotics for gastroenteritis?
C. diff
Immunocompromised patients
Some very ill with campylobacter
Which microorganism would you suspect for someone who has been at a BBQ and thought the burgers looked funny?
E. coli
Which microorganism would you suspect for someone who had been at a Chinese buffet/had reheated a takeaway with rice?
Bacillus cereus
Which microorganism would you suspect for someone remembers eating a cream cake that had been left out?
Staph aureus
Which microorganism would you suspect for someone at a care home where many of its residents have diarrhoea and some aren’t urinating?
HUS - E. coli
Cholera key points
Usually from water contaminated with faeces
Rice-water stools
Describe the microorganism cholera
Gram negative bacillus
Is cholera toxin mediated?
Yes
Enteric fever key points
Fever, headache, abdominal discomfort
SE Asia or Indian subcontinant
Isolate patient immediately
What are the two microorganisms that could be causing enteric fever and which is less severe?
Salmonella typhoid Salmonella paratyphoid (less severe)
Enteric fever clinical findings?
Abdominal tenderness
Hepatosplenomegaly
How is enteric fever diagnosed?
Blood culture
What antibiotic is given for enteric fever if stable, unstable (septic) or from an area of resistance?
Stable - ciprofloxacin
Unstable - ceftriaxone
Resistant - azithromycin
Amoebiasis key points
Protozoa
Poor sanitation
May cause abscess
In abscess caused by amoebiasis, what are the physical signs?
Dark patch in liver and abdominal discomfort
Point of tenderness over right lover ribs
What are the investigations for amoebiasis?
Stool microscopy CT to see abscess AXR to check for toxic mega-colon CXR - raised right semi-diaphragm May need endoscopy or biopsy
What is the management for amoebiasis?
Metronidazole
Paramomycin to clear the gut lumen of parasites
Giardiasis key points
Protozoa
Faecal-oral spread
Watery, malodorous diarrhoea, bloating and flatulance
Symptoms of giardiasis
Watery, malodorous diarrhoea
Bloating and flatulence
Abdominal cramps
Weight loss
Investigation for giardiasis
Stool microscopy for cysts
Stool PCR when available
Treatment for giardiasis
Metronidazole or tinidazole
What are helminth infections associated with?
Eosinophilia
How would you get schistosomiasis?
Swimming in Lake Malawi
How would you get a tapeworm?
Undercooked meat
