Enterobacteriaceae

Question 1

General properties of enterobacteriaceae (6)

Answer 1

1. They are aerobes or facultative anaerobes.
2. They are all motile by peritrichous flagella except shigella and klebsiella
3. They are catalase positive and oxidase negative
4. They ferment glucose with the production of acid or gas.
5. They reduces nitrates to nitrites
6. They are all negative gram bacilli.

Question 2

Give 8 genera of enterobacteriaceae

Answer 2

1. Escherichia
2. Klebsiella
3. Edwardsiella
4. Citrobacter
5. Enterobacter
6. Protea
7. Salmonella
8. Shigella

Question 3

Lactose fermenter gives what colour in macconkey agar?

Answer 3

Pink

Question 4

Non-Lactose fermenter gives what colour in macconkey agar?

Answer 4

Colourless

Question 5

Examples of lactose fermenter? 4

Answer 5

1. E. Coli( motile)
2. Klebsiella(non-motile)
3. Enterobacter
4. Citrobacter

Question 6

Example of non lactose fermentor?

Answer 6

1. proteus( motile and h2s produce)
2. Morganella
3. Providencia
4. Salmonella( motile and h2s produce)
5. Shigella(non-motile and non h2s produce)
6. Yersinia( non motile and non h2s produce)

Question 7

Species under escherichia?

Answer 7

E. Coli

Question 8

Species under klebsiella?

Answer 8

1. K. Hafnia

2. K. Serratia

Question 9

Species under protea?

Answer 9

1. Proteus
2. Morganella
3. Providencia

Question 10

Characteristics of E. coli?

Answer 10

1. Gram negative bacilli
2. facultative anaerobes
3. Bactericides species : E.coli in GIT = 20:1
4. O(outer membrane), H(flagella), and K(capsular) antigen = 700 serotypes
5. Oxidase -ve
6. Catalase +ve
7. Ferment glucose,lactoseand can generate energy by reducing nitrates to nitrites.
8. MacConkey agar- pink colonies
9. Eosin Methylene Blue agar- metalllic shine appearance on colonies

Question 11

Classification of E.coli

Answer 11

Kingdom : bacteria
Phylum : proteobacteria
Class : gamma proteobacteria
Order : ennterobacteriales
Family : enterobacteriaceae
Genus : escherichia
Species : Escherichia coli

Question 12

Virulent factors of E.coli

Answer 12

• they have pyelonephritis-associated Pili (P Pili)
  
  • contain serotype of E.coli
  • binds to galactose disaccharide receptors of urinary tact epi
• most important in UTI
• type I pile
• bind to the D-mannose Receptor on epithelial cell surfaces
• CFA(colonising factor antigen ) or BFA(bundle forming antigen )
• binds to enterocytes
• NOn Fmbrial adhesion (intimin)
• siderophores-helps in iron absorption
• capsule ( K antigen)
• k1 capsule in neonatal meningitis
• inhibit antibodies and complement attachment to the bacterial surfaces, inhibit phagocytosis
• O antigen
• outermembrane
• endotoxin
• H antigen
• flagella
• motility and invasive disease
• alpha-hemolysins
• pore formation or membrane , toxic to many mammalian cells
• lyse lymphocytes, beta-hamolysins, inhibit phagocytosis and chemotaxis of neutrophils

Question 13

Types of exotoxins secreted by E.coli

Answer 13

1. Heat labile enterotoxin (LT)
   - similar function to the cholera toxin
   - binds to ganglioside receptor on enterocytes
   - deactivated in high temp
2. Heat stable toxin (ST)
   - binding to guanylate cyclase receptors on the apical membranes of host cells, thereby activating the enzyme- diarrhoea
   - resistance to boiling 30 degree Celsius
3. Shiga toxins ( verotoxin)
   - decrease protein synthesis by destructing 28S ribosome
   - Hemolytic UreameS (HUS) syndrome
   - secreted byO157 : H7 serotype