17 - E Coli

Question 1

What are the features of EColi e.g shape and gram stain?

Answer 1

Enterobacteriaceae means it can use lactose

Question 2

What would E Coli look like under the microscope?

Answer 2

Question 3

How can you identify E.Coli without a gram stain in the lab?

Answer 3

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

Question 4

How can you distinguish between different strains of E.coli?

Answer 4

Question 5

Where are the different antigens on E.Coli?

Answer 5

Question 6

What are some of the diseases that E.Coli can cause?

Answer 6

• Diarrhoea
• UTI
• Blood stream infection
• Neonatal meningitis
• Can protect against pathogenic invasion of pathogens like salmonella when a normal commensal of bowel

Question 7

What are the most common strains of E.Coli that cause diarrhoea?

Answer 7

• ETEC
• EPEC
• EAEC
• EIEC
• DAEC
• STEC

Question 8

What is the major cause of traveller’s diarrhoea and how does it cause disease?

Answer 8

• 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

Question 9

What complications does shiga toxin producing E coli cause?

Answer 9

• Haemorrhagic colitis
• Haemolytic uraemic syndrome (triad of acute renal failure, haemolytic anamia and thrombocytopenia)

Question 10

How does the Shiga Toxin cause virulence?

Answer 10

• 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

Question 11

What are some of the virulence factors of E.coli (ExPEC)?

Answer 11

Question 12

How does E.coli cause urinary infections?

Answer 12

• 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

Question 13

Apart from UTIs and diarrhoea what other common infection can E.Coli cause?

Answer 13

Most common cause of blood stream infection leading to SEPSIS

Question 14

How can you prevent and treat traveller’s diarrhoea?

Answer 14

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

Question 15

How can you treat UTI caused by E. COLI?

Answer 15

• Trimethoprim or Nitrofurantoin as majority are resistant to first now

Question 16

What antibiotic should you not use for E.Coli blood stream infections?

Answer 16

• Coamoxiclav as it is becoming resistant due to horizontal gene transfer