Sheila M. Martin-Corbin
Bacteria causes disease by invasion of the cell and toxin production. These invasive bacteria establish a protected niche, within which they survive and replicate inside the cell, causing an infection. When bacteria invade a host, injury to and destruction of the host cell and tissues occurs at the site of invasion. The ultimate result of bacterial invasion is due in greater part to the location of the disease process and how critical the involved tissues are to the survival of the host.
Bacteria may be surrounded by three surface layers namely, a capsule, cell wall and cell membrane. The cell wall is composed of complex carbohydrates and surrounds the cell membrane of the cell. It also protects the bacterium from injury and regulates the movement of molecules into and out of the cell. When the cell wall of the bacteria is weakened or damaged by antibiotics such as penicillin, it will render the bacteria less virulent and harmful to its victim.
In pathogenic bacteria, virulence may be related to the presence of a capsule which protects the cell from phagocytosis. Hence, the loss of the capsule may result in a parallel loss of virulence. If the wall of a bacterium is damaged or removed, significant morphologic alterations may occur.
2