Enterobacteriaceae Identification

Laboratory testing algorithm for E. coli, Enterobacter aerogenes, Klebsiella pneumoniae, Serratia marcescens, Proteus vulgaris, and Proteus mirabilis

Gram Stain
Gram Negative Rods

Oxidase Test
Negative

Enterobacteriaceae

MacConkey Agar
Positive Lactose - - Positive indole

Escherichia coli

MacConkey Agar - Positive Lactose
Indole Negative - - Urea Negative

Enterobacter aerogenes

MacConkey Agar - Positive Lactose
Indole Negative - - Urea Positive

Klebsiella pneumoniae

MacConkey Agar - Growth
H₂S Negative
Negative Lactose - - Citrate Positive

Serratia marcescens

MacConkey Agar - Negative Lactose
H₂S Positive - - Indole Positive

Proteus vulgaris

MacConkey Agar - Negative Lactose
H₂S Positive - - Indole Negative

Proteus mirabilis