Cytotoxic activity of coagulase-negative staphylococci in bovine mastitis

Songlin Zhang, Carol W. Maddox

Research output: Contribution to journalArticlepeer-review


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 mastiffs. 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.

Original languageEnglish (US)
Pages (from-to)1102-1108
Number of pages7
JournalInfection and immunity
Issue number3
StatePublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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