GI Microbiology Flashcards
The factor of foreign travel implies what?
Traveller’s diarrhoea: entertoxigenic E. coli
South east Asia: vibrio species
South America, Asia, Africa: rotavirus
A recent course of antibiotics implies what?
An increased risk of Clostridium difficile infection
Daycare exposure implies what?
Rotavirus
Exposure to raw seafood implies what?
Non-cholera vibrio
Patients who have anal receptive sex (MSM) implies what?
Shigella
Campylobacter
Salmonella
Patient’s with a HIV-positive status implies what?
Mycobacterium avium-intracellular complex
Cytomegalovirus
Giarda
What do outbreaks imply?
Cruise ships - norovirus
Contaminated local source: campylobacter, E. coli
Bacillus cereus
Gm + bacillus In starchy foods like rice Has heat resistant spores Causes profuse vomiting Short incubation 1-6 hours
Staphylococcus aureus
Gm + coccus
Source: food left at room temp (milk, meat, fish)
It’s toxin is pre-formed in food causing rapid absorption
Acts on VC and also causes abdo pain
Shigella
Endemic in the developing world
Shiga toxin will bind to receptors on renal cells, RBCs, and others inhibiting protein synthesis and causing cells death
E. Coli 0157
Suspect: bloody diarrhoea/blood PR Very low infectious dose Source: wide range of food, person to person and animal contact 50% of cases < 16 years old Highest rate < 5 years old
Haemolytic Ureamic Syndrome
8-15%of E. coli 0157cases within 2 weeks
Symptoms and signs: abdo pain, fever, pallor, petechiae, Liguria, bloody diarrhoea, increased WBC, decreased platelets, red cell fragments, LDH > 1.5x normal
What are the investigations for HUS?
Stool samples U&Es FBC clotting Urine Lactate dehydrogenase
What do you not do for HUS?
No antibiotics
No anti motility
No NSAIDS
Campylobacter
Incubation: 16-48 hours
Source: food; raw poultry, raw milk
Symptoms and signs: pain, blood (30%), fever
Treatment: macrolides (if co-morbid factors but increasingly resistant)
Most common GI infection, it has small pathogen numbers and is invasive
Less likely to spread from person to person
Salmonella enteritis
Incubation: 12-48 hours
Source: food; poultry, meat, raw eggs; animal gut, multiplies in food
Symptoms and signs: diarrhoea and vomiting, blood, fever
Typing salmonella
Different antigens on the body, called O antigen
Antigen agglutinates with corresponding antibody
Serogrouping salmonellae can help pinpoint the source of infection
Groups B, C & D are most common locally/
Serogroups are further divided by looking at antigens on the tail
Listeria monocytogenes (Gastroenteritis)
Incubation: 9-48 hours
Symptoms and signs: fever, muscle aches, diarrhoea, pregnant women may have mild symptoms
Source: unpasteurised milk products, deli counter
“Fridge bacteria”
Listeria monocytogenes (Gastroenteritis)
2-6 weeks
Patients at risk: immunosuppressive (esp. T cell), age >50, pregnancy
Diagnosis of Listeria
Easier from sterile site
Gm + rod
Cold enrichment
Culture
Rotavirus
Commonest in kids < 3 Almost all kids get it before 5 Spread: person to person, faecal-oral Usually in the winter Can be severe in the immunocompromised Symptoms: moderate fever, vomiting, diarrhoea, NOT bloody Self-limiting, lasts a week Low infectious dose, survives in the environment Hydration is key management
Norovirus
Affects all ages: highly infectious
Route: faecal-oral droplet, person to person, environmental survival on fomites
Low infectious dose
Diarrhoea and vomiting, explosive and sudden
Lasts 2-4 days, usually self limiting
Early ward closure/isolation/cohorting required
