Identification of Staphylococus aureus genes expressed during growth in milk : a useful model for selection of genes important in bovine mastitis?

Staphylococcus aureus is a major cause of bovine mastitis. Since gene expression of many bacteria is known to be regulated by the environment, milk may play an important role in the regulation of the early steps in the pathogenesis of bovine mastitis by S. aureus. To get insight into the response of S. aureus to the milk environment, a Tn917-lacZ mutant library was generated and screened for genes specifically expressed during growth in milk. Twenty-eight mutants were identified and analysed. Four groups of genes were found, involved in cell-wall synthesis, nucleotide synthesis, transcriptional regulation and carbohydrate metabolism. A fifth group contained genes with hypothetical or unknown functions. Many of the genes identified belonged to biosynthetic pathways of S. aureus and other bacterial species which have also been shown to play a role in vivo as determined in murine infection models. Therefore, growth on milk may be an attractive model for the identification of genes preferentially expressed during bovine mastitis

Identification of Staphylococus aureus genes expressed during growth in milk : a useful model for selection of genes important in bovine mastitis?

Staphylococcus aureus is a major cause of bovine mastitis. Since gene expression of many bacteria is known to be regulated by the environment, milk may play an important role in the regulation of the early steps in the pathogenesis of bovine mastitis by S. aureus. To get insight into the response of S. aureus to the milk environment, a Tn917-lacZ mutant library was generated and screened for genes specifically expressed during growth in milk. Twenty-eight mutants were identified and analysed. Four groups of genes were found, involved in cell-wall synthesis, nucleotide synthesis, transcriptional regulation and carbohydrate metabolism. A fifth group contained genes with hypothetical or unknown functions. Many of the genes identified belonged to biosynthetic pathways of S. aureus and other bacterial species which have also been shown to play a role in vivo as determined in murine infection models. Therefore, growth on milk may be an attractive model for the identification of genes preferentially expressed during bovine mastitis

Cell tropism of Staphylococcus aureus in bovine mammary gland cell cultures

Staphylococcus aureus is one of the most important pathogens of the bovine mammary gland. The interaction of S. aureus with cells of the bovine mammary gland is considered to play an essential role in the pathogenesis. In this study, we identified a new target cell for S. aureus adhesion and invasion. For that purpose, cells which compose the alveoli of the mammary gland were cultured. In these cultures, two morphologically different cell types, elongated and cubic cells, were observed. Adhesion and invasion of S. aureus was studied using microscopical and microbiological methods. S. aureus adhered specifically and in large numbers (about 300 bacteria/cell) to the elongated cell type. No adhesion to the cubic cell type was observed. In addition, bacteria were also found intracellularly in the elongated cells, and enclosed in membrane vesicles. Adhesion and invasion were time dependent and reached maximum levels after 4 h. Invasion was strongly reduced by staurosporine and genistein. The newly identified target cell was further characterized

Cell tropism of Staphylococcus aureus in bovine mammary gland cell cultures

Staphylococcus aureus is one of the most important pathogens of the bovine mammary gland. The interaction of S. aureus with cells of the bovine mammary gland is considered to play an essential role in the pathogenesis. In this study, we identified a new target cell for S. aureus adhesion and invasion. For that purpose, cells which compose the alveoli of the mammary gland were cultured. In these cultures, two morphologically different cell types, elongated and cubic cells, were observed. Adhesion and invasion of S. aureus was studied using microscopical and microbiological methods. S. aureus adhered specifically and in large numbers (about 300 bacteria/cell) to the elongated cell type. No adhesion to the cubic cell type was observed. In addition, bacteria were also found intracellularly in the elongated cells, and enclosed in membrane vesicles. Adhesion and invasion were time dependent and reached maximum levels after 4 h. Invasion was strongly reduced by staurosporine and genistein. The newly identified target cell was further characterized