Staphylococcus epidermidis tests positive for coagulase prod

Staphylococcus epidermidis tests positive for coagulase production which can be seen by the zone of hydrolysis on a blood agar plate.

Select one: True or False

If the bacteria growing on the EMB can make lactose the colonies will take up the eosin and methylene blue dyes.

Select one:

True

False

Solution

True. Cogulase enzyme causes fibrin of blood plasma to clot. It leads to hydrolysis of blood.

EMB is a selective stain for gram negative bacteria.. Bacteria growing on EMB should be able to make lactase enzyme which ferments lactose to produce acid which lowers the pH and thus encourages dye absorption by colonies.

Hence fermentation of lactose is must for dye absorption.