HardyDisk™ Lysostaphin Differentiation Disks are used to rapidly differentiate Staphylococcus spp. and Micrococcus spp. based on lysostaphin resistance.
Susceptibility to lysostaphin is a rapid test method in differentiating staphylococci from micrococci. Other differentiation tests, such as glucose fermentation, bacitracin or furazolidone susceptibility tests require at least 24 hours incubation. In contrast, the lysostaphin disk test is a 2.5 hour test.The peptidoglycan in the cell walls of most Staphylococcus contain an interpeptide bridge consisting of glycine-rich peptides. Lysostaphin is an endopeptidase that cleaves these peptide linkages, rendering the cells susceptible to osmotic lysis (lysostaphin susceptible). The interpeptide bridge of Micrococcus does not contain glycine. Since the presence of glycine is essential for the action of lysostaphin, the Micrococcus cells are not affected and are lysostaphin resistant.)
Each HardyDisk™ Lysostaphin Differentiation Disk is a filter paper disk (0.25 inch in diameter) containing 20ug of lysostaphin.
Specimen Collection: This product is not intended for the primary isolation of patient specimens. It should be used only with cultures of isolated organism. This product is used in conjunction with other biochemical tests to identify cultures of isolated organism.1. Allow disks to equilibrate to room temperature before opening vial.2. Using a pure 18-24 hour culture, prepare a heavy suspension (equivalent in density to a McFarland 2.0 standard) in 2ml of sterile saline.3. Transfer 1ml of the bacterial suspension into a second test tube.4. Add one lysostaphin disk to one of the bacterial suspensions and shake vigorously. Use the second suspension as a negative control.5. Incubate both suspensions aerobically at 35-37 degrees C. for 2.5 hours in an incubator, or for 2 hours in a 35-37 degrees C. waterbath. Do not disturb suspension before 2 hours.6. After incubation, compare the turbidity of the bacterial suspension with the lysostaphin disk against the control suspension.
INTERPRETATION OF RESULTS
Positive Reaction: Complete clearing of the bacterial suspension or marked decrease in its turbidity as compared with the negative control suspension, indicates susceptibility to lysostaphin (Staphylococcus spp.).Negative Reaction: The suspension remains turbid and does not clear, indicates resistance to lysostaphin (Micrococcus spp.).
Cat. no. HDZ112
Size: 50 disks/vial