Escherichia Coli

Question 1

What is the gram stain of E.coli?

Answer 1

Gram negative bacilli

Question 2

What is escherichia coli?

Answer 2

Gram negative bacilli
Lactose fermenting - use lactose of energy source
Anaerobic

Question 3

What can E. Coli cause?

Answer 3

Diarrhoea
Extra-intestinal infections e.g. UTIs

Question 4

Transmission of E. Coli

Answer 4

Hand to mouth contact
Consumption of contaminated food

Question 5

Identifying E. coli in a lab

Answer 5

Grow as pink colonies on MacConkey agar as lactose fermenters - lactic acid changes colour
Pink gram negative bacilli gram stain

Question 6

Colour of lactose fermenting colonies on MacConkey agar

Answer 6

Pink
Produce lactic acid&raquo_space; changes colour of indicator

Question 7

Colour of non-lactose fermenting colonies on MacConkey agar

Answer 7

Yellow

Question 8

Explain the colour change in MacConkey agar

Answer 8

Contains lactose and pH indicator
pH indicator goes red with acid pH

Pink - lactose fermenting colonies
Yellow - non-lactose fermenting colonies

Question 9

How does serology work with E. Coli?

Answer 9

Using antibodies to detect different bacterial surface antigens
K - capsule
O - LPS (lipopolysaccharide)
F - fimbriae
H - flagella

Question 10

Where is E.coli normal in body?

Answer 10

In large bowel

Question 11

What is a potential function of E.coli?

Answer 11

Protection against invasion by pathogenic species e.g. salmonella

Question 12

What are the 6 pathotypes of diarrhoeagenic E. Coli that cause diarrhoea?

Answer 12

Enterotoxigenic E. Coli (ETEC)
Enteropathogenic E. Coli (EPEC)
Enteroaggregative E. Coli (EAEC)
Enteroinvasive E. Coli (EIEC)
Diffusely adherent E. Coli (DAEC)
Shiga toxin producing E. Coli (STEC)

Question 13

What are the most common E. Coli pathotypes in children in developing world?

Answer 13

Enteropathogenic E. Coli (EPEC)
Enteroinvasive E. Coli (EIEC)

Question 14

What is the most common E. Coli pathotype in immunocompromised persons?

Answer 14

Enteroaggregative E. Coli (EAEC)

Question 15

What does enterotoxigenic E. Coli cause?

Answer 15

Travelers’ diarrhoea

Question 16

What is the most common cause of travellers’ diarrhoea?

Answer 16

Enterotoxigenic E. Coli

Question 17

Transmission of Enterotoxigenic E. Coli?

Answer 17

Faecal-oral

Question 18

What toxins are produced from enterotoxigenic E. Coli?\

Answer 18

Heat stable toxin (ST)
Heat liable toxin (LT)

Question 19

What effect of enterotoxigenic E. Coli toxins have?

Answer 19

• Stimulate the lining of intestines
• Cause them to secrete excessive fluid&raquo_space; profuse water diarrhoea and abdominal cramping

Question 20

What effect do heat stable toxins and heat liable toxins have?
What produce them?

Answer 20

• Stimulate the lining of intestines
• Cause them to secrete excessive fluid producing profuse water diarrhoea and abdominal cramping

Enterotoxigenic E. Coli

Question 21

What does Enteropathogenic E. Coli cause?

Answer 21

• The localised disappearance of microvilli
• Attaches to the host cell surface&raquo_space; forming attaching and effacing lesions.

Question 22

What are other names for shiga toxin producing E. Coli?

Answer 22

Verocytotoxic E. Coli (VTEC)
Enterhaemorrhagic E. Coli (EHEC)

Question 23

What does shiga toxin producing E. coli cause?

Answer 23

Haemorrhagic colitis&raquo_space; bloody diarrhoea
Haemolytic uraemic syndrome

Question 24

What is haemolytic uraemic syndrome?

Answer 24

Triad of conditions:
- Acute renal failure
- Haemolytic anaemia
- Thrombocytopenia

Question 25

Explain the invasion of shiga toxin producing E.coli

Answer 25

- B sub unit of shiga toxin binds to Gb3 on host cell surface - toxin is endocytosed + transported to Golgi apparatus + endoplasmic reticulum - during transports, the A chain is cleaved into A2 fragment + enzymatically active A1 fragment - A fragments held together by disulfide bonds until toxin reaches ER where A1 fragment is released - A1 fragment goes to cytosol - A1 fragment inactivates ribosome >> inhibits protein synthesis >> cell death

Question 26

What strain of E. Coli causes extra intestinal diseases?

Answer 26

Extra-intestinal pathogenic E. Coli (ExPEC)

Question 27

What does extra-intestinal pathogen E. Coli cause?

Answer 27

Disease outside intestinal tract

Question 28

Virulence factors for extra-intestinal infections

Answer 28

Adhesions Iron acquisition systems Protections invasions Toxins

Question 29

Why are UTIs more likely in women than men?

Answer 29

Anatomical differences between women and men Shorter and easier route for bacteria to enter urethra from rectum in women

Question 30

Complications of cystitis

Answer 30

Frequent + urgent urination Dysuria - painful Nocturia - wake up in night Hematuria - blood Malaise

Question 31

Symptoms of pyelonephritis

Answer 31

Back and/or flank pain Fevers + chills Nausea Vomiting Anorexia

Question 32

Prevention of E. Coli caused diarrhoea

Answer 32

- Avoid food + drink that could be contaminated *e.g. raw meat, seafood + poultry, unpasteurised dairy products, street food, untreated water in areas lacking chlorination* - Wash hands

Question 33

Treatment of E. Coli caused diarrhoea

Answer 33

- Most will recovered after a few days without treatment - Clear liquids to prevent dehydration + loss of electrolytes - oral rehydration solution - Avoid antibiotics

Question 34

Treatment of UTIs

Answer 34

Antibiotics *trimethoprim nitrofurantoin*

Question 35

Why are urine samples in labs unrepresentative of the majority of UTIs?

Answer 35

They are often UTIs which haven’t resolved Have antibiotic resistant bacteria

Question 36

Virulence factors of uropathogenic E. coli

Answer 36

Adhesions Lipopolysaccharide

Question 37

What is the classification of microbes of E. Coli?

Answer 37

Prokaryote (bacteria)

Question 38

What is the mode of action of trimethoprim?

Answer 38

Inhibits folic acid synthesis