ADHERENCE OF STAPHYLOCOCCUS-AUREUS TO CULTURED BOVINE MAMMARY EPITHELIAL-CELLS

Bovine mammary secretory cells, isolated at necropsy, were cultured in vitro and used as a model to study the mode of adherence of Staphyloc occus aureus to mammary epithelium. Cultured cells were characterized by their morphology and physiology as secretory epithelial cells. Cell s showed characteristic growth patterns when grown on polystyrene, fib ronectin, laminin, collagen, and reconstituted basement membrane from the Engelbreth-Holm-Swarm murine sarcoma. Cells cultured on collagen f ormed confluent monolayers and were the most suitable for bacterial ad herence studies. Cultured cells stained intensely for cytokeratin and for specific milk proteins, i.e., alpha-casein, beta-casein, alpha-lac talbumin, beta-lactoglobulin, and lactoferrin. The effect of frozen st orage for 10 mo on cell viability or presence of milk proteins was min imal. Staphylococcus aureus showed large affinity for extracellular ma trix components, i.e., fibronectin, laminin, and collagen. Adherence t o confluent cell monolayers was minimal. In preconfluent cell monolaye rs, most S. aureus adhered more readily to the exposed matrix than to the epithelial cells. Overnight exposure to staphylococcal alpha-toxin greatly increased adherence of S. aureus to confluent monolayers. How ever, whether bacteria adhered to alpha-toxin damaged cells or to expo sed matrix is not clear. Unencapsulated S. aureus adhered in larger nu mbers than did encapsulated S. aureus.