17 - E Coli Flashcards
What are the features of EColi e.g shape and gram stain?
Enterobacteriaceae means it can use lactose
What would E Coli look like under the microscope?
How can you identify E.Coli without a gram stain in the lab?
MacConkey agar containing lactose. If they use lactose they produce lactic acid and this turns the agar red as it has a low pH. If not lactose fermenting they grow yellow colonies
How can you distinguish between different strains of E.coli?
Where are the different antigens on E.Coli?
What are some of the diseases that E.Coli can cause?
- Diarrhoea
- UTI
- Blood stream infection
- Neonatal meningitis
- Can protect against pathogenic invasion of pathogens like salmonella when a normal commensal of bowel
What are the most common strains of E.Coli that cause diarrhoea?
- ETEC
- EPEC
- EAEC
- EIEC
- DAEC
- STEC
What is the major cause of traveller’s diarrhoea and how does it cause disease?
- ETEC (enterotoxigenic e coli)
- Faecooral transmission
- Produces two toxins, heat stable ST and heat labile LT, that stimulate lining of intestines to secrete excess fluid so cramping and diarrhoea
- 3-4 days
What complications does shiga toxin producing E coli cause?
- Haemorrhagic colitis
- Haemolytic uraemic syndrome (triad of acute renal failure, haemolytic anamia and thrombocytopenia)
How does the Shiga Toxin cause virulence?
- Binds to receptor
- Endocytosis
- Cleaved in vesicle to form small A fragments that translocate into cytosol and A1 inactivates ribosomes inhibiting protein synthesis so cell death
What are some of the virulence factors of E.coli (ExPEC)?
How does E.coli cause urinary infections?
- Transfer from rectum to urethra and then migrate to blader
- UPC has adhesins called type 1 fimbria that can bind to uroepithelium to form communities, LPS toxin, cytotoxin alpha-haemolysin and produce siderophores to sequester iron to survive
Apart from UTIs and diarrhoea what other common infection can E.Coli cause?
Most common cause of blood stream infection leading to SEPSIS
How can you prevent and treat traveller’s diarrhoea?
Prevent:
- Avoid food and drink that may be contaminated
- Raw fruit and veg and ice from places with poor chlorination
Treatment:
- Fluids
- Oral rehydration tablets
- Avoid antibiotics
How can you treat UTI caused by E. COLI?
- Trimethoprim or Nitrofurantoin as majority are resistant to first now
What antibiotic should you not use for E.Coli blood stream infections?
- Coamoxiclav as it is becoming resistant due to horizontal gene transfer
