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Enterobacteriaceae 2

Enterobacteriaceae Identification: Key Findings

SpeciesAppearance on MediaBiochemical Test Results
Klebsiella Highly mucoid colonies on all media. lactose fermenter non-motile / Urease +
Enterobacter and Pantoea Mucoid as Klebsiella Usually motile – Differentiate from Klebsiella which is non-motile, also a difference in amino acid utilization
Serratia Some strains produce bright red pigment on media (Red pigment in Serratia marcescens) May appear lactose non-fermenter, but is a slow fermenter Colony appearance will help distinguish it from Klebsiella and Enterobacter Motile MR – mostly negative VP – Pos/Var – 61% positive Citrate + S. marcescens = lysine +, ornithine + S. liquefaciens = lysine -, ornithine –
Proteus “Swarming” on BAP due to high motility of organism Lactose non-fermenter H2S + (may be confused with Salmonella) Urease + - tell from Salmonella Indole = to speciate; + = P. vulgaris/- = P. mirabilis Highly motile
Providencia Similar to Proteus, but no swarming urease - = Providencia stuartii - differentiate from Proteus (other species are urease +) motile - moves but doesn't swarm indole +
Morganella Similar to Proteus, but no swarming Urease + = no swarming to tell from Proteus Motile Indole + MR + VP – = Proteus can be VP + Citrate -
Citrobacter Slow lactose fermenter on MacConkey Clear on SS and HE Indole = C. freundii -, C. koseri + Citrate + ( hence the name)- Shigella is Citrate - = differentiates
Yersinia Bullseye colony on CIN Grows best at room temp. Indole = variable MR = + VP = - Citrate = -
E. coli Lactose fermenter - flat pink colony on MacConkey Irridescent “sheen” on EMB agar Blood Agar - round smooth grayish colonies with distinct edge. May be beta-hemolytic. Yellow on HE and XLD E. coli O157:H7 - clear on Sorbitol MacConkey Motile Indole + Citrate - Ferment a wide variety of sugars Very Susceptible to antibiotics
Created by: nbechen3