Bacteria typically adhere to various cell surfaces present in the human body to colonise or invade human tissues. Staphylococcus aureus (S. aureus) can express the fibronectin-binding proteins A and B (FnBP-A, FnBP-B) that can facilitate the binding of multiple copies of fibronectin (Fn). In addition, Fn bound to the bacterium trigger activation of α5β1 integrins found on the cells and facilitate invasion of human cells. Although the invasion mechanisms regarding signalling pathways and overall host cell interactions have been defined, the quantitative relationship between the mediators of invasion and the temporal kinetics has not yet been elucidated. In this thesis, newly developed microscopy-based methods have been used to quantify the interactions between H1299 cells and S. aureus at various Fn concentrations. After an approximate Fn concentration of 15 μg/ml, the S. aureus bacteria strains become saturated both for the wildtype and the negative control strains. Additionally, using the step-by-step protocol developed during this study, adhesion of the wildtype strain of S. aureus with 15 μg/ml Fn is occurring on the H1299 cells. Although adjustments to the protocol are needed, this adhesion mechanism will lead to an internalisation of the S. aureus strains to the H1299 cells.