4.3: Mannitol Salt agar Flashcards
Mannitol salt agar (MSA) contains:
-the carb mannitol
-7.5% sodium chloride (NaCl)
-pH indicator phenol red
Mannitol provides the substrate for ?? and makes the medium ??
-fermentation
-differential
NaCl makes the medium ?? because its concentration is high enough to dehydrate and kill most bacteria
-selective
Phenol red indicates whether fermentation with an acid end product has taken place by changing color as the ?? changes
-pH
Yellow color=
red color=
pink color=
-acid (ferments mannitol)
-neutral (does not ferment mannitol)
-alkaline (does not mannitol)
Differential media is a media that:
-Display distinct characteristics between different microorganisms
Selective media is a media that:
-Favors the growth of some microorganisms and inhibits others
When a Mannitol Salt Agar plate turns yellow, this indicates:
-an acidic pH
TRUE OR FALSE:
Mannitol salt agar is both selective and differential.
-TRUE
What is the purpose of adding salt to mannitol salt agar?
-High concentrations of salt inhibit the growth of non-halophilic organisms but allow for the growth of bacteria from the genus Staphylococci.
TRUE OR FALSE:
The sodium chloride in the mannitol salt agar is high enough to dehydrate and kill most bacteria except those in the genus Staphylococcus
-true
When a Mannitol Salt Agar plate turns pink, this indicates:
-do not ferment Mannitol
TRUE OR FALSE:
The 7.5% sodium chloride in the mannitol salt agar is high enough to dehydrate and kill most of the non-halophilic bacteria
-true
The mannitol in the Mannitol Salt Agar plate serves as
-a carbohydrate food source
You have a bacteria that in the Gram stain, the cells appear as purple cocci, many in grape-like clusters. On a Mannitol Salt Agar plate, the organism grows well and turns the plate yellow. A likely suspect is`
-Staphylococcus aureus
