Describe the basis for selectivity of EMB agar Mac con key a

Describe the basis for selectivity of EMB agar Mac con key agar and mannitol Salt agar. Aurine with UTI (Urinary track infection) should be plated on MacConkeyAgar. Why?

Solution

Basis of selectivity of EMB agar containing the dyes; methylene blue and eosin; is that it inhibits the Gram-positive bacterial growth thus it is selective in allowing the growth of only Gram-negative bacteria.

MacConkey agar allows the growth of only coliforms and enteric pathogens that can ferment lactose, hence it is selective.

Mannitol Salt Agar is selective for the isolation of Staphylococci bacteria as the e high concentration of salt in this media is tolerated by the Staphylococci others perish.

Q10. Aurine with UTI should be plated on MacConkey agar since most of the UTI are caused by E.coli that are lactose fermenting and hence develop pink color when the urine sample of a UTI is placed in MacConkey agar hence selected by the medium.