Enterobacteriaceae Lab Identification Flow Chart

Question 1

H2S + K/A Possible organisms

Answer 1

Proteus
Edwardsiella
Salmonella
Citrobacter freundii

Question 2

Proteus biochemical characteristics

Answer 2

H2S +
K/A
PAD +
*P. vulgaris is A/A

Question 3

How can you differentiate between Proteus mirabilus and Proteus vulgaris?

Answer 3

P. vulgaris: indole + orthinine -

P. mirabilis: indole- orthinine +

Question 4

Salmonella biochemical characteristics

Answer 4

K/A 
H2S + 
PAD - 
Lysine decarboxylase + (except paratyphi A) 
Indole -

Question 5

Edwardsiella biochemical characteristics

Answer 5

K/A 
H2S + 
PAD - 
Lysine decarboxylase + 
Indole +

Question 6

Citrobacter freundii

Answer 6

K/A H2S + (can be A/A)
PAD -
Lysine decarboxylase -

Question 7

A/A H2S - Possible organisms

Answer 7

Escherichia coli
Enterobacter
Klebsiella
Serratia

Question 8

Escerichia coli biochemical characteristics

Answer 8

A/A H2S - (can also be K/A)
IMV:C ++- -
*all that is needed

Question 9

Klebsiella biochemical characteristics

Answer 9

A/A H2S -
IMV:C - - ++
Non-motile @ 37 C

Question 10

Serratia biochemical characteristics

Answer 10

A/A H2S - (can also be K/A)
IMV:C - - ++
Motile at 37 C
DNAse + (unique to species)

Question 11

Enterobacter biochemical characteristics

Answer 11

A/A H2S -
IMV:C - - ++
Motile at 37 C
DNAse -

Question 12

K/A H2S - Possible species

Answer 12

Shigella 
Yersinia pestis 
Serratia *
Escherichia coli *
Providencia 
Morganella

Question 13

Shigella biochemical characteristics

Answer 13

K/A H2S -
PAD -
Nonmotile at 37 C
Urease -

Question 14

Yersinia biochemical characteristics

Answer 14

K/A H2S -
PAD -
Nonmotile at 37 C (some spp. motile at 25 C)
Urease +

Question 15

Providencia biochemical characteristics

Answer 15

K/A H2S -
PAD +
Citrate +

Question 16

Morganella biochemical characteristics

Answer 16

K/A H2S -
PAD +
Citrate -