Streptococcus species possesses a wide variety of virulence factors and can cause severe invasive infections. Accordingly, the field of bacterial pathogenesis has rapidly expanded with a greater understanding of pathogenesis at the molecular level over the last decades. The ability of bacteria to cause disease is described in terms of the number of infecting bacteria, the route of entry into the body, the effects of host defense mechanisms, and intrinsic characteristics of the acteria called virulence factors. One essential prokaryotic cell function is the transport of proteins from the cytoplasm into other compartments of the cell, the environment, and/or other bacteria or eukaryotic cells a process known as protein secretion.Secreted proteins can play many roles in promoting bacterial virulence, from enhancing attachment to eukaryotic cells, to scavenging resources in an environmental niche, to directly intoxicating target cells and disrupting their functions. Virulence factors encoded on pathogenic islands represent the entire spectrum of bacterial virulence factors, from adhesins ,toxins, secretion systems, invasins, modulins, effectors, proteases, lipases, and enterotoxins, superantigens, iron uptake systems, immunoglobulin A proteases, capsule synthesis, host defense avoidance mechanisms.