Lecture 9 E.Coli

Question 1

What are the general properties of enterobacteriaceae (7)

Answer 1

1. Facultatively anaerobic
2. Peritrichous flagella if motile
3. Simple nutritional needs
4. Oxidase negative
5. Don’t form spores
6. Cause nearly half of all infections in modern hospitals
7. Type species: E.coli

Question 2

What are pathogenic properties of Enterobacteriaceae (3)

Answer 2

1. In normal flora in GIT
2. Opportunistic pathogens (hospitals), causes septicaemia, UTIs, pneumonia and wound infections,
3. Includes somespecies which can cause diarrhoea, dysentry and bubonic plague

Question 3

Describe the 4 steps of infection for E.coli - septicaemia,

Answer 3

1. Entry - throat or infected bladder (GIT)
2. Attachment - none, protected by capsule
3. Spread - via blood
4. Multiplication - doesnt need to as infected at low conc

Question 4

Describe the virulence factors and how disease is caused by E.coli - septicaemia

Answer 4

Virulence factors 
1. Capsule
2. Serum resistance
3. Haemolysin production
4. enhanced iron uptake systems 
Disease caused by endotoxins

Question 5

Describe the 4 steps of infection for E.coli - UTIs

Answer 5

1. Entry - GIT to bladder

2. Attachment, Spread and multiplication: Invasion of mucosa of bladder –> cell death and inflammation

Question 6

Describe the virulence factors and how disease is caused by E.coli - UTIs

Answer 6

Virulence factors:
1. fimbrae/pili
2. capsule
Catheters compromise urinary tract infections

Question 7

Describe the infection process by E.coli - peritonitis, appendicitis, abscesses and
wound infections

Answer 7

E.coli works in synergy with strict anaerobes (E.coli uses oxygen and anaerobes supply growth factors)

1. Entry from GIT
2. Multiplication - synergy between E.coli and strict anaerobes.

Question 8

What are enteric diseases caused by E.coli

Answer 8

Strains of E. coli which cause diarrhoea in healthy humans making them true pathogens not opportunists.
Example Shiga toxin-producing E.coli (EHEC)

Question 9

What is EHEC

Answer 9

E.coli strain which are true pathogens that cause septicaemia or affect the large intenstine

Question 10

Whats haemolytic uraemic syndrome?

Answer 10

Shiga toxins (produced by EHEC in GIT) damage kidney cells which results in platelet and fibrin deposition which can either

1. Injure RBC (results in haemolysis)
2. Decreased glomerular filtration and kidney failure.

Question 11

What are the virulence factors of EHEC

Answer 11

1. Intimin - binds to epithelial cells in large intenstine
2. Shiga toxins
3. Haemolysin - lyses RBC
   Many strains of E.coli produce shiga toxins, but often lack intimin and haemolysin and are unable to cause bloody diarhoea

Question 12

Define Diarhoea and Dysentry

Answer 12

Diarrhoea - abnormal faecal discharge with frequent fluid stool
Dysentry - Inflammatory disease of GIT resulting in bloody faeces and abdominal cramps

Question 13

Define enteritis and gastroenteritis

Answer 13

Enteritis - Inflammation of intestine

Gastroenteritis - intenstinal infection characterised with nausea, vomiting and diarrhoea

Question 14

Define colitis and enterocolitis

Answer 14

Colitis - inflammation of large intestine

Enterocolitis - inflammation involving mucus of small and large intestine