invasiveness

Invasiveness refers to the ability of a pathogenic organism to penetrate and grow within a host, moving away from the initial site of infection. This quality is a significant factor in virulence, which is the degree of toxicity or injury-producing potential of a microorganism.12

While little is known about the specific factors that enable invasiveness, some organisms produce enzymes that break down host tissues, creating pathways for spread. For example, the bacterium causing syphilis has a high degree of invasiveness, capable of penetrating intact skin. In contrast, the diphtheria bacterium has low invasiveness, only infecting surface cells, with its damage primarily caused by an exotoxin. Viruses' invasiveness is aided by their small size, and for fungi and parasites, it relates to their life cycle, using spores or smaller reproductive forms to enter the body. In cancer, microinvasion involves cancer cells detaching, breaking through membranes, and moving through tissues, aided by enzymes that digest the extracellular matrix.234