The use of a lysostaphin fusion protein as a dry-cow treatment for chronic Staphylococcus aureua mastitis in dairy cattle
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This study evaluated the efficacy of a lysostaphin-fusion protein (Lyso-PTD) as a dry-cow therapy for the treatment of experimentally-induced chronic, subclinical Staphylococcus aureus mastitis. Twenty-two Holstein dairy cows were experimentally infected with Staph aureus in a single pair of diagonal mammary quarters approximately 45 d before dry-off. Staphylococcus aureus infected mammary quarters of cows were randomly assigned to one of two groups at dry-off 1) 279 mg of Lyso-PTD in 50 mL of vehicle (n = 11 cows; 22 quarters) or 2) 50 mL of vehicle solution (n =11 cows; 22 quarters) by intramammary infusions. All cows were followed for 30 d post-partum to determine cure rates using bacteriologic culture, somatic cell counts, and clinical mastitis scores. No cures were recorded in either the treatment or control groups. Milk somatic cell count, bacterial colony counts, and mastitis scores did not significantly differ between groups (P = 0.832, P = 0.117, and P= 0.108, respectively). Follow-up studies in lactating cows revealed neither increasing the Lyso-PTD dose to 1340mg nor treatment with cephapirin sodium showed improved efficacy. In conclusion, Lyso-PTD was not an effective dry-cow therapeutic for chronic, subclinical Staph. aureus mastitis at the experimental dose and formulation used.
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