Growth of Staphylococcus epidermidis in soft agar in relation to respiration, dehydrogenase activity and biotype

Using 200 fresh isolates of Staphylococcus epidermidis, the relationship between type of growth in soft-agar medium and respiration, dehydrogenase activity and biotype was investigated. When strains of S. epidermidis were cultured in Brain Heart Infusion medium containing 0.15% (w/v) agar, the following different growth types were observed: compact colonial morphology with growth throughout the medium (type A), or with growth only at the surface (type B); and diffuse colonial morphology with growth throughout the medium (type C), growth only at the surface (type D), or growth from the surface to the middle of the tube (type E). Five representative strains of each growth type were studied and different results for cytochrome pattern, oxygen consumption and relative activities of lactic dehydrogenase and succinic dehydrogenase were obtained with different growth types. However, there was no correlation between growth type and biotype.