The virulence is an agent of an infection to produce disease, the virulence of bacteria is a measure of the severity of the disease it causes. Bacterial virulence factors are exotoxins, virulent surface protein, and virulent enzyme, capsule, adhesins, and lipopolysaccharides. Virulence factors help bacteria to invade the host, cause disease, and evade host defences. Virulence factors that promote bacterial colonization.