MP2X Agar

Description

This cherry red agar is prepared from a modified Columbia agar base with the addition of 5% washed bovine erythrocytes and contains esculin. The red cells allow for the best possible detection of β-hemolytic zones that will surround the colony on the majority of Staphylococcus aureus strains.  This agar also contains a special chromogen. All Staphylococcus aureus strains will react to the chromogen and produce a green or blue-green colony color. MP2X will also grow other gram positive Staphylococci, Streptococci, and Enterococci bacteria. Some Streptococci will react with the chromogen and appear dark blue, or may hydrolyze esculin, causing a background blackening (including Streptococcus uberis and Enterococcus spp.), but all Streptococci growth will be catalase negative. This selective agar will inhibit the growth of all gram-negative Enterobacteriaceae and Pseudomonas organisms.

All green colonies that show the β-hemolytic zone should be categorized as Staphylococcus aureus. Some non–β-hemolytic Staphylococcus strains will also produce a green colony and will require a secondary coagulase test. Any non–β-hemolytic Staphylococcus green colony (either alpha or non-hemolytic) that is coagulase positive should be categorized as Staphylococcus aureus. Any non–β-hemolytic green Staphylococcus colony that tests coagulase negative should be categorized as Staphylococcus species. There is no need to perform coagulase test on non-green colonies.

Refer to the table on back for the expected culture responses.