In order for pathogenic bacteria to invade a cell, communication with the host cell is required.  The first step for invading bacteria is usually adhesion to host cells.  Strong anchoring, a characteristic that determines virulence, prevents the bacteria from being washed away before infection occurs. Bacterial cells can bind to many host cell surface structures such as glycolipids and glycoproteins which serve as attachment receptors. Once attached, the bacteria begin to interact with the host to disrupt its normal functioning and disrupt or rearrange its cytoskeleton. Proteins on the bacteria surface can interact with protein receptors on the host thereby affecting signal transduction within the cell.  Alterations to signaling are favorable to bacteria because these alterations provide conditions under which the pathogen can invade.  Many pathogens have Type III secretion systems which can directly inject protein toxins into the host cells. These toxins ultimately lead to rearrangement of the cytoskeleton and entry of the bacteria.