Slime production and biofilm forming ability by Staphylococcus aureus bovine mastitis isolates

In this study we investigated the ability of slime production and biofilm formation in 70 subclinical and clinical bovine mastitis isolates Staphylococcus aureus. Slime production was determined from colony morphology of isolates in Congo red agar. The ability of biofilm formation was assessed in a quantitative assay using a microtiter-plate test involving crystal violet stailing and for selected strains, scanning electron microscopy on stainless steel coupons was done. Eight Staphylococcus aureus isolates (11.42%) formed black colonies of dry consistency, characteristic for slime-producing strains. According to the result of microtitel plate test, 9 isolates (12.86%) were categorized as strong biofilm producers, 21 (30%) as moderate, and 40 (57.14%) as weak biofilm producers. Scanning electron microscopy revealed differences between investigated isolates with respect to their ability to colonize stainless steel surfaces and to form a three-dimensional biofilm structure.