6) Micro Bio Lab Practical (Bile Esculin & Plaque Assay)

What is the purpose of Bile Esculin Agar?

To select for the growth of enterococcus for presumptive ID

What does Oxgall (bile salts) do in Bile Esculin?

Selective ingredient; Inhibit Gram (+), except Enterococcus

What does sodium azide do in bile esculin?

Selective ingredient; inhibits gram (-)

What does esculin do in bile esculin agar?

Differential ingredient; has glucose and is a special food source, differential for E. faecalis

What does ferric citrate do in bile esculin agar?

Turns brown with esculetin (product of esculin digestion)

What does non-brown growth in Bile esculin agar mean?

Enterococcus, but NOT E. faecalis

What does brown growth in bile esculin agar mean?

Presumptive E. faecalis

What is the “M” protein in blood agar?

Discovered by Rebecca Lancefield

Has anti-phagocytic properties

What is the purpose of the plaque assay?

To determine the titer (PFU/mL) of the original phage stock solution

What is a PFU?

Plaque forming unit