Evaluation of trehalose-mannitol broth for differentiation of Staphylococcus epidermidis from other coagulase-negative staphylococcal species.

Trehalose-mannitol agar and various broth formulations thereof were evaluated for the differentiation of Staphylococcus epidermidis from other common coagulase-negative staphylococcal species isolated from human blood cultures. While this differentiation was accurately made on trehalose-mannitol agar in 18 h, modification of the medium to a broth formulation containing 2% each trehalose and mannitol in 0.2 ml of purple broth base provided greater than 95% accuracy when a heavy inoculum was incubated on a rotary shaker for at least 4 h.