title: Synergistic streptococcal phage λSA2 and B30 endolysins kill streptococci in cow milk and in a mouse model of mastitis.
abstract: Bovine mastitis results in billion dollar losses annually in the USA alone. Streptococci are among the most relevant causative agents of this disease. Conventional antibiotic therapy is often unsuccessful and contributes to development of antibiotic resistance. Bacteriophage endolysins represent a new class of antimicrobials against these bacteria. In this work, we characterized the endolysins (lysins) of the streptococcal phages λSA2 and B30 and evaluated their potential as anti-mastitis agents. When tested in vitro against live streptococci, both enzymes exhibited near-optimum lytic activities at ionic strengths, pH, and Ca(2+) concentrations consistent with cow milk. When tested in combination in a checkerboard assay, the lysins were found to exhibit strong synergy. The λSA2 lysin displayed high activity in milk against Streptococcus dysgalactiae (reduction of CFU/ml by 3.5 log units at 100 μg/ml), Streptococcus agalactiae (2 log), and Streptococcus uberis (4 log), whereas the B30 lysin was less effective. In a mouse model of bovine mastitis, both enzymes significantly reduced intramammary concentrations of all three streptococcal species (except for B30 vs. S. dysgalactiae), and the effects on mammary gland wet weights and TNFα concentrations were consistent with these findings. Unexpectedly, the synergistic effect determined for the two enzymes in vitro was not observed in the mouse model. Overall, our results illustrate the potential of endolysins for treatment of Streptococcus-induced bovine mastitis.
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, North East Area, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Ave, Beltsville, MD, 20705, USA. mathias.schmelcher@hest.ethz.ch.|Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, LFV B18, 8092, Zurich, Switzerland. mathias.schmelcher@hest.ethz.ch.
authors.forename: Mathias
authors.initials: M
authors.lastname: Schmelcher
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, North East Area, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Ave, Beltsville, MD, 20705, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Powell
authors.affiliation: Statistics Group, Office of the North East Area Director, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Ave, Beltsville, MD, 20705, USA.
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Camp
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, North East Area, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Ave, Beltsville, MD, 20705, USA.|North Carolina State College of Veterinary Medicine, 1060 William Moore Drive, Raleigh, NC, 27607, USA.
authors.forename: Calvin S
authors.initials: CS
authors.lastname: Pohl
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, North East Area, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Ave, Beltsville, MD, 20705, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Donovan
mesh_terms: D000818:Animals; D058491:Bacterial Load; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D004195:Disease Models, Animal; D004357:Drug Synergism; D010450:Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D042361:Mammary Glands, Human / Q000382:microbiology; D008413:Mastitis / Q000188:drug therapy* / Q000382:microbiology; D051379:Mice; D050296:Microbial Viability / Q000187:drug effects*; D008892:Milk / Q000382:microbiology*; D009994:Osmolar Concentration; D013290:Streptococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013291:Streptococcus / Q000187:drug effects*; D017108:Streptococcus Phages / Q000201:enzymology*; D016896:Treatment Outcome
chemical_list: D010450:Endopeptidases; C001143:endolysin; D002118:Calcium
keywords: Antimicrobial; Bacteriophage; Endolysin; Mastitis; Peptidoglycan hydrolase; Streptococcus