Mannitol Salt Agar (MSA)

These flashcards cover key concepts related to Mannitol Salt Agar, its selective and differential properties, and the results of microbial growth on this medium.

Mannitol Salt Agar (MSA)

A selective medium that inhibits growth of Gram negative species and selects for Gram positive Staphylococcus species.

Selective Property of MSA

High Salt Content (7.5% NaCl), which inhibits growth of organisms that cannot survive high salt conditions.

Differential Property of MSA

Mannitol fermentation, indicated by the presence of mannitol as a substrate.

Indicator for MSA

Phenol Red, which changes color based on the pH level.

Positive Result for Staphylococcus aureus on MSA

Growth with yellow color indicates mannitol fermentation and a drop in pH.

Positive Result for non-Staphylococcus aureus on MSA

Growth with red color indicates Gram positive Staphylococcus species other than Staphylococcus aureus.

Negative Result for MSA

No growth indicates presence of Gram negative species, which do not thrive in high salt conditions.

Indicator Color Change in MSA

Turns yellow if mannitol fermentation occurs; remains red if no fermentation occurs.