A recombinant
mucolytic protein,
lysostaphin, was evaluated as a potential intramammary therapeutic for Staphylococcus aureus
mastitis in dairy cattle.
Lysostaphin, a product of Staphylococcus simulans, enzymatically degrades the cell wall of Staphylococcus aureus and is bactericidal. Thirty Holstein-Freisian dairy cattle in their first lactation were infected with Staphylococcus aureus (Newbould 305, ATCC 29740) in all quarters.
Infections were established and monitored for somatic cell counts and Staphylococcus aureus colony-forming units 3 wk prior to subsequent treatment. Infected animals were injected through the teat canal with a single dose of recombinant
lysostaphin (dose response 1 to 500 mg) or after three successive p.m. milkings with 100 mg of recombinant
lysostaphin in 60 ml of sterile
phosphate-buffered saline. Animals were considered cured if the milk remained free of Staphylococcus aureus for a total of 28 milkings after last treatment. Kinetic analysis of immunologically active recombinant
lysostaphin demonstrated that a minimum bactericidal concentration was maintained in the milk for up to 36 to 48 h after a single infusion of 100 mg of recombinant
lysostaphin. The cure rate of quarters receiving recombinant
lysostaphin (100 mg in sterile
phosphate-buffered saline, administered over three consecutive p.m. milkings) was 20% compared with 29% for
sodium cephapirin in saline and 57% for a commercial
antibiotic formulation, respectively. An improved formulation of recombinant
lysostaphin may prove to be an effective alternative to
antibiotic therapy for
bovine mastitis.