Escherichia Coli

Question 1

Describe the structure of E. Coli

What sugar does it use?
What is the waste product?

Answer 1

Gram negative rods (bacilli)

Lactose
Lactic acid

Question 2

Compare the apperance of E Coli and Pseudomonias aeruginosa on a MacConkey agar plate (Contains lactose and pH indicator)

Answer 2

E Coli goes pink (due to lactic acid)

PA: Goes yellow

Question 3

E Coli has 4 serotypes according to the Serological Antigens. (K, O, F, H)

What cellular structures are associated with each of the 4 Serological Antigens

Answer 3

O- LPS
K- Capsule
F- Fimbriae
H- Flagella

Question 4

There are 6 types of E. coli that can cause diarrhoea

Name them

Answer 4

1. ETEC (Enterotoxigenic)
2. EPEC (Enteropathogenic)
3. EAEC (Enteroaggregative)
4. EIEC (Enteroinvasive)
5. DAEC (Diffusely adherent)
6. EHEC/ STEC/ VTEC (Enterohaemorrhagic/ Shiga toxin producing/ Verocytotoxin producing)

Question 5

In the developing word, what 2 forms of diarrhoea causing E. coli are the most common?

Which form is most common amongst Immunocompromised people?

Answer 5

EPEC and EIEC

EAEC

Question 6

What form of E. coli is the leading cause of travellers’ diarrhoea?

What 2 toxins does it produce?

Answer 6

ETEC

Heat stable toxin (ST
Heat labile toxin (LT)
Can secrete either/ both of these)

Question 7

List 9 clinical signs of infection by ETEC

Answer 7

• Diarrhoea (most common)
• Abdominal cramping (most common)
• Fever
• Nausea (with/ without vomiting)
• Chills
• Appetite loss
• Headache
• Muscle aches
• Bloating

Question 8

What is the incubation period of infection by ETEC? How long does it last?

Answer 8

Onset after 1-3 days

Lasts 3-4 days

Question 9

Which form of E Coli is responsible for UTIs

Answer 9

UPEC (Uropathogenic)

Question 10

Name 4 virulence factors of UPEC causing;

• Cystitis
• Pylonephritis

Answer 10

Cystitis;

• Adhesins
• Toxins
• Siderophores (iron complexing proteins) (as iron availability is extremely restricted in urinary tract)
• Capsule

Pyelonephritis;

• Adhesins
• Toxins
• Siderophores
• Flagella

Question 11

Which bacteria are the commonest cause of bloodstream infection in England?

Answer 11

E Coli

Question 12

What are 2 methods of managing diarrhoea-causing E Coli infections

Answer 12

• Prevention (avoid food and drinks that could be contaminated)
• Treatment ( Most will recover in a few days without specific treatment, rehydration, antibiotics may make illness worse)

Question 13

What are 2 antibiotics commonly used to treat UTIs caused by E Coli

Answer 13

Trimethoprim and Nitrofurantoin

60% of E Coli urine samples are resistant to trimethoprim