Enterobacteriaceae (Intro stuff)

Question 1

List the general characteristics of Enterobacteriaceae. (Gram stain,morphology,oxidase test,capsulation,motility,glucose fermentation test,nitrate reductase test)

Answer 1

• Gram negative, rod shaped
• Facultative anaerobes
• Oxidase negative (lack cytochrome oxidase)
• Non-capsulated except Klebsiella and some strains of E.coli
• Most are motile except Shigella and Klebsiella
• Ferment glucose with acid production
• Most reduce nitrate to nitrite via nitrate reductase

Question 2

List the lactose fermenters.

Answer 2

• Escherichia coli
• Klebsiella spp
• Citrobacter spp
• Enterobacter spp

Question 3

List non-lactose fermenters.

Answer 3

*Salmonella spp.
*Shigella spp
*Proteus spp
*Yersinia spp

Question 4

Appearance of lactose fermenters on MacConkey. (colour)

Answer 4

Red

Question 5

Appearance of non-lactose fermenters on MacConkey. (colour)

Answer 5

colourless/transparent

Question 6

Describe components of antigenic structure.

Answer 6

• Lipopolysachharide /O antigen: a single organism may carry several O antigens
• Capsular/K antigen: Prevent O agglutination
• Flagella/H antigen
• Outer membrane proteins Pili