4. Lysostaphin sensitivity.
Transfer isolated colony from agar plate with inoculating loop to 0.2 ml phosphate-saline buffer, and emulsify.
Transfer half of suspended cells to another tube (13 x 100 mm) and mix with 0.1 ml phosphate-saline buffer as control.
Add 0.1 ml lysostaphin (dissolved in 0.02 M phosphate-saline buffer containing 1% NaCl) to original tube for concentration of 25 µg lysostaphin/ml.
Incubate both tubes at 35°C for not more than 2 h.
If turbidity clears in test mixture, test is considered positive. If clearing has not occurred in 2 h, test is negative.
S. aureus is generally positive.