|HOERNIG, K.J. - University Of Missouri|
|PITHUA, P. - University Of Missouri|
|WILLIAMS, III, F. - University Of Missouri|
|MIDDLETON, J.R. - University Of Missouri|
Submitted to: Journal Dairy Science Supplement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2015
Publication Date: 6/1/2016
Citation: Hoernig, K., Pithua, P., Williams, Iii, F., Donovan, D.M., Middleton, J. 2016. Evaluation of a lysostaphin-fusion protein as a dry-cow therapy for Staphylococcus aureus mastitis in dairy cattle. Journal Dairy Science Supplement. 99(6):4638-46.
Interpretive Summary: Disease of the cow mammary gland (mastitis) is a world-wide problem for dairy production costing the US dairy industry up to 2 billion dollars a year of lost revenue. Identifying novel antimicrobials for use against mastitis pathogens is an important goal of agricultural research. Staphylococcus aureus is a notorious bacterial mastitis pathogen. It resides in both the mammary gland lumen (extracellular in milk) or can invade and reside within (intracellular) bovine mammary gland cells. Lysostaphin is a antimicrobial enzyme that kills S. aureus. This work describes the therapeutic use of a fusion protein consisting of lysostaphin fused to a protein transduction domain (PTD) [this domain facilitates the (intracellular) uptake of lysostaphin into mammary cells]. The lysostaphin-PTD was used to treat 11 dairy cattle that were infected with S. aureus, vs. 11 infected controls treated with just buffer alone. The intent was that lysostaphin-PTD would kill both extracellular and intracellular S. aureus. No cures were recorded in either the treatment or control groups. In conclusion, Lysostaphin-PTD was not an effective dry-cow therapeutic for chronic, subclinical S. aureus mastitis at the 279 mg/50 ml buffer dose. This indicates that more extensive analysis of PTD-fusion constructs is required to identify a novel antimicrobial that will treat both intracellular and extracellular S. aureus mastitis.
Technical Abstract: 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 infusion. 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). In conclusion, Lyso-PTD was not an effective dry-cow therapeutic for chronic, subclinical Staph. aureus mastitis at the tested dose and formulation.