title: Cytotoxic activity of coagulase-negative staphylococci in bovine mastitis.
abstract: Secreted toxins play important roles in the pathogenesis of bacterial infections. In this study, we examined the presence of secreted cytotoxic factors of coagulase-negative staphylococci (CoNS) from bovine clinical and subclinical mastitis. A 34- to 36-kDa protein with cell-rounding cytotoxic activity was found in many CoNS strains, especially in Staphylococcus chromogenes strains. The protein caused cell detachment and cell rounding in several cell lines, including HEp-2, Int 407, CHO-K1, and Y-1 cells. Native protein recovered from nondenatured polyacrylamide gel electrophoresis showed both cytotoxic activity and casein hydrolysis activity. The purified protein had a pH optimal at 7.2 to 7.5 and a pI of 5.1 and was heat labile. The proteolytic activity could be inhibited by zinc and metal specific inhibitors such as 1, 10-phenanthroline and EDTA, indicating that it is a metalloprotease. Protein mass analysis and peptide sequencing indicated that the protein is a novel metalloprotease. Different bacterial strains expressed variable levels of 34- to 36-kDa protease, which may provide an indication of strain virulence.
authors.affiliation: Animal Diagnostic Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zhang
authors.forename: C W
authors.initials: CW
authors.lastname: Maddox
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000633:toxicity*; D016466:CHO Cells; D002417:Cattle; D003030:Coagulase / Q000032:analysis*; D006224:Cricetinae; D005260:Female; D006801:Humans; D008414:Mastitis, Bovine / Q000382:microbiology*; D008666:Metalloendopeptidases / Q000633:toxicity*; D008970:Molecular Weight; D013210:Staphylococcus / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D001427:Bacterial Toxins; D003030:Coagulase; D008666:Metalloendopeptidases