Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/2006
Publication Date: N/A
Technical Abstract: Bovine mastitis (mammary gland infections) exists on every dairy farm, affects 1/3 of the animals, and costs the US dairy industry about $2 Billion annually. There are multiple mastitis-causing pathogens but streptococci and staphylococci are the most predominant. Broad spectrum antibiotics are often less than 50% effective, with culling often necessary. Transgenic cattle resistant to S. aureus mastitis challenge have been created via mammary gland expression of a peptidoglycan (PG) hydrolase (lysostaphin) that is lytic for S. aureus cell walls (Nat. Biotechnol. 23:445-51). Phage endolysins are a prodigious source of novel PG hydrolases that often contain two discrete enzymatic domains that each target a unique bond in the PG. We have performed deletion analysis and site-directed mutagenesis to show that the streptococcal phage B30 endolysin Acm glycosidase (lysozyme-like) domain, although highly conserved and enzymatically active on cell wall preparations, does not contribute significantly to cell lysis. Fusions of PG hydrolase domains have been shown to maintain their domain-specific hydrolytic activities. Fusing either the highly active B30 CHAP endopeptidase domain or the full length B30 endolysin to full length lysostaphin creates an antimicrobial that is active against both S. aureus and several streptococci. This designer antimicrobial approach demonstrates the facility of constructing highly specific antibacterial proteins that target multiple unrelated pathogens simultaneously.