Bacteria photos: Staphylococci

Staphylococcus aureus and Staphylococcus epidermidis on Baird Parker agar; lecithinase production and lipase activity

staphylococcus aureus and staphylococcus epidermidis on baird parker agar

Staphylococcus aureus and S.epidermidis on Baird Parker agar plate. Cultivation 24 hours, aerobic atmosphere, 37°C.

Lithium chloride and potassium tellurite act as selective agents. Egg yolk is the substrate to detect lecithinase production and lipase activity. Staphylococci produce dark gray to black colonies due to tellurite reduction; staphylococci that produce lecithinase break down the egg yolk and cause clear zones around respective colonies (S.aureus positive, S.epidermidis negative). An opaque zone of precipitation may form due to lipase activity (S.aureus positive, S.epidermidis negative).