17. E. coli

Question 1

What are the main features of E. coli?

Answer 1

Gram negative rods - pink
Typically lactose-fermenting
Facultatively anaerobic 
Often motile
Numerous serotypes

Question 2

How is E. coli identified in the lab?

Answer 2

As they can use sugar lactose as an energy source, prodding lactic acid as a asteroid product
Pseudomonas aeruginosa cannot use lactose
MacConkey agar contains lactose and a pH indicator that goes red with acid pH
E. coli grow as pink colonies on MacConkey agar, non-lactose fermenters grow as yellow colonies

Question 3

What are the serological antigens of E. coli?

Answer 3

K - capsule
O - LPS (causes septic shock)
F - fimbriae (adhesion to cell surfaces)
H - flagella (motility)

Question 4

What are the benefits of E. coli?

Answer 4

Normal component of large bowel microbiota in humans

Possible protects against invasion by pathogenic species such as salmonella

Question 5

What can E. coli cause?

Answer 5

Intestinal infections - diarrhoea
Toxin-mediated disease
Extra-intestinal infections - UTI, intra-abdominal, biliary tract, bloodstream infection, neonatal meningitis

Question 6

What are the 6 pathotypes of diarrhoeagenic E. coli?

Answer 6

Enterotoxigenic E. coli (ETEC)
Enteropathogenic E. coli (EPEC)
Enterooaggregative E. coli (EAEC)
Enteroinvasive E. coli (EIEC)
Diffusely adherent E. coli (DAEC)
Shiga toxin-producing E. coli (STEC)

Question 7

Which are the most common E. coli causing bacteria in children?

Answer 7

EPEC

EIEC

Question 8

How is ETEC transmitted?

Answer 8

Faeco-oral

Question 9

How does ETEC cause diarrhoea?

Answer 9

ETEC produces 2 toxins (ST and LT)
Toxins stimulate the lining of the intestines causing them to secrete excessive fluid producing profuse watery diarrhoea and abdominal cramping

Question 10

What does STEC cause?

Answer 10

Causes haemorrhage colitis and haemolytic uraemia syndrome (triad of acute renal failure, haemolytic anaemia and thrombocytopenia)

Question 11

What are the virulence factors for extra-intestinal pathogenic E. coli?

Answer 11

Adhesins
Iron acquisition systems
Protectins and invasins
Toxins

Question 12

What are the clinical symptoms of cystitis?

Answer 12

Frequent urgent urination
Dysuria, suprapubic pain
Nocturia, haematuria, malaise

Question 13

What are the clinical symptoms of pyelonephritis?

Answer 13

Back and/or flank pain
Fever, chills, malaise
Nausea, vomiting, anorexia

Question 14

What is the prevention for E. coli infections?

Answer 14

Avoid foods and drink that could be contaminated with bacteria
Raw fruit and vegetables, raw seafood or undercooked meat or poultry

Question 15

What is the treatment for E. coli infections - diarrhoea?

Answer 15

Most infected persons will recover within a few days without requiring any specific treatment
Clear liquids are recommended for persons with diarrhoea to prevent dehydration and loss of electrolytes
Oral rehydration solutions

Question 16

What are the commonly used antibiotics for UTIs?

Answer 16

Trimethoprim

Nitrofurantoin