Mannitol salt agar (MSA) plates are a selective and differential solid culture medium containing a high concentration of sodium chloride, mannitol (as a fermentable carbohydrate), and phenol red (a pH indicator). The elevated salt concentration inhibits the growth of most Gram-negative and Gram-positive bacteria, while allowing salt-tolerant organisms, particularly staphylococci, to grow.

MSA differentiates organisms based on their ability to ferment mannitol. Mannitol-fermenting bacteria, such as Staphylococcus aureus, produce acid that turns the medium yellow, while non-mannitol fermenters remain pink or red. Because of these properties, MSA plates are foundational media for the isolation, differentiation, and presumptive identification of Staphylococcus in clinical, environmental, and industrial microbiology applications.

Our mannitol salt agar (MSA) plates are supplied as ready-to-use pre-poured plates, eliminating in-house media preparation and reducing variability between workflows. Each MSA plate provides a consistent salt concentration, reliable pH-indicator performance, and clear differentiation.

We manufacture our complete catalog of MSA plates using validated processes and rigorous quality control testing to ensure sterility, performance, and lot-to-lot consistency. We also support custom manufacturing options, including modified MSA formulations, alternative plate formats, antibiotic combinations, peptone substitutes, and bulk quantities to support specialized clinical, food testing, or research workflows.