**6.2 Lysostaphin as an anti-staphylococcal therapeutic agent**

Lysostaphin is a potent staphylococcus-degrading enzyme containing a peptidase that can specifically cleave the polyglycine bridge specific to the cell wall of *Staphylococcus aureus*. Lysostaphin activity is measured by its ability to lyse *Staphylococcus aureus* cells. It is influenced by enzyme concentration, pH, temperature, ion and salt concentration. *Staphylococcus aureus* is enveloped in a thick layer of peptide glycans, and lysostaphin destroys the layer of peptide glycans, causing lysis and cell death. Peptide glycans impart strength and rigidity to the cell walls of gram-positive microorganisms, grow and divide, maintain cell shape, and prevent osmotic lysis of *Staphylococcus aureus*. Recombinant lysostaphin (rLYS) is a zinc metal enzyme that hydrolyzes the glycylglycine bond of a peptide glycan to a pentaglycine bridge on the cell wall of *Staphylococcus aureus*. A rodent model was used for the treatment of mastitis. The first study of rLYS in the sand showed that the rate of reduction of udder infection was over 87%, and the activity of dissolving stones in the body had a detrimental effect on the host. Instead, it reveals that it is a traditional antibacterial agent. Efficacy of rLYS in lactating dairy cows with experimentally induced *Staphylococcus aureus* infection. At least one intra-mammary

injection of 100 mg rLYS95 in 60 ml phosphate buffered saline (PBS) cures 95% of udder infection with *Staphylococcus aureus*. The antibacterial activity of rLYS *in vitro* persisted for 72 hours, but *in vivo* most of the infected mammary glands remained in the body for 72 hours after treatment [59].
