Tellurite-glycine agar: a selective plating medium for the quantitative detection of coagulase-positive staphylococci.

The coagulae-positive staphylococci comprise a very homogeneous, readily identifiable species (Evans and Niven, 1950; Shaw et al., 1951) that includes all of the proven pathogenic and enterotoxin-producing strains of staphylococci. As a result of the clinical and public health significance of these organisms, a selective medium for their isolation and enumeration would have considerable value. Chapman (1945, 1946, 1948) has proposed several media that are selective for staphylococci and have some value in differentiating between coagulase-positive and coagulase-negative strains. The selective action of these media is based on a high sodium chloride content and the use of mannitol as an energy source. Their differential value is based on orange pigmentation, acid production from mannitol, and gelatin hydrolysis by coagulase-positive strains. However, not all such strains have these characteristics, and numerous coagulase-negative strains posse some or all of these characteristics. Thus it is frequently necesary to isolate a considerable number of pure cultures from these media and apply the coagulase test to these isolates. A more selective medium has been proposed by Ludlam (1949). This medium includes tellurite and lithium chloride as selective agents and the pH of the medium was adjusted to 9.6 before sterilizing. This medium was found to be quite satisfactory for the isolation of coagulasepositive staphylococci from air, skin surfaces, the nose, and stool specimens (Duguid and Wallace, 1948; Ludlam, 1949). However, Chapman (1949) and McDivitt and Hussemann (1954)