Enterobacteriaceace; general info

Question 1

Gram pos. or neg. ?

Answer 1

Gram negative bacteria

Question 2

Habitat

Answer 2

Gut, environment, normal gut flora, mucous membranes, skin, food, water

Question 3

Morphology

Answer 3

• 1-3um rods
• Capsule
• Fimbria
• Flagella (except Shigella, Klebsiella)

Question 4

Staining

Answer 4

Gram-negative

Question 5

Culture

Answer 5

• Simple (not fastidious), facultative anaerobic, 10-45 C (optimal is 37C)
• Selective and differential media
• Selective enrichment -> Salmonella
• Combined media

Question 6

Culture; selective and differential media -> low selective capacity

Answer 6

• Crystal violet-lactose-litmus (Drigalski)
• Crystalviolet - bile salts (inhibitory of gram+) - lactose (lactose fermentation) - neutral red (MacConkey) as indicator
• Eosin - lactose - methylene blue - Na lauryl sulphate

Question 7

Culture; selective and differential media -> medium selective capacity

Answer 7

• Some of the enterobacteria
• Brilliant green - lactose - phenol red
• Deoxychocolate citrate - lactose (lactose fermentation)- neutral red (DC)
• XLD: xylose - lysine - deoxycholate -> for diff. of E. Coli

Question 8

Culture; selective and differential media -> high selective capacity

Answer 8

• Isolation of Salmonella, isolation from mixed culture. Only selective genera can grow here
• Bismuth - sulphite agar: lactose fermentation, way of disticntion, produce acid from lactose
• Chromogenic media - detection of specific enzymes: Salmonella, E.Coli

Question 9

Mac Conkeys agar, colors when neg, pos and uninoculated?

Answer 9

Uninoculated: brown-pink
Neg: brown-yellow
Pos: Pink

Question 10

Biochemistry

Answer 10

• Catalase +
• Oxidase -
• Fermentative (acid+gas)

Question 11

Antigens

Answer 11

4 types: 
O: cell wall (lipopolysaccharide-LPS)
K: capsule (polysaccharide) some enterobacteria has capsule
H: flagella (protein) virulence factor
F: fimbria (protein) virulence factor

Question 12

Resistance

Answer 12

Fair, medium, non-spore forming

Question 13

Pathogenicity

Answer 13

Obligate pathogenic

• Facultative pathogenic: majority, predisposed factors sometimes needed
• Saprophytes: normal gut flora (gut, mucous membranes)

Question 14

Grouping based on; biochemical characteristics

Answer 14

Genus

Question 15

Grouping based on; biochemical and serological characteristics

Answer 15

Species

Question 16

Grouping based on; O antigens (cell wall antigens)

Answer 16

Serogroups, within species

Question 17

Grouping based on; O-K-H-F antigens

Answer 17

Serotype

Question 18

Grouping based on; fermentation pattern

Answer 18

Biotypes

Question 19

Genera of the family Enterobacteriaceae is based on?

Answer 19

Lactose positive or Lactose negative

Question 20

Genera of the family Enterobacteriaceae; Lactose positive

Answer 20

• Escherichia
• Klebsiella
• Enterobacter

Question 21

Genera of the family Enterobacteriaceae; Lactose negative

Answer 21

• Salmonella
• Shigella
• Yersinia
• Proteus (saprophyte)
• Providencia (saprophyte)
• Citrobacter (saprophyte)
• Edwardsiella (fish, water))
• Serratia (fish, water)

Question 22

Keypoints of enterobacteria (5)

Answer 22

• Gram-negative rods
• Most are motile
• Grow on nutrient agar or MacConkey agar
• Aerobic, facultative anaerobic
• Catalase +, Oxidase -

Question 23

Major enteric and systemic pathogens?

Answer 23

• Escherichia coli
• Salmonella enterica
• Yersinia species

Question 24

Opportunistic pathogens?

Answer 24

• Klebsiella species
• Enterobacter species
• Proteus species
• Serratia species