Health Conditions

What causes it?

Bacteria cause disease in two ways: they release toxins that harm and kill body cells, and they provoke the immune system, leading to inflammation, which can in itself be harmful.

	Bacteria release toxins that enter cells and kill them.

The body's first reaction to a bacterial invasion, as in any injury, is a general inflammatory reaction. Blood vessels in the area of the infection widen to increase the supply of white blood cells that fight infection. Blood proteins, called complement, are released into the system. Complement either kills the bacteria directly or attracts immune cells called phagocytes, which ingest and kill the bacteria. The body then produces more immune cells, including white blood cells called T cells, which kill foreign substances in the body. T cells stimulate other white blood cells called B cells to secrete specific antibodies. Antibodies are molecules that the body's immune system uses to identify a particular invader. Over a person's lifetime, the immune system develops millions of antibodies. In response to a bacterial invasion, the antibodies bind to bacteria and then attract complement and phagocytes, which kill the bacteria.

When bacteria enter the body and multiply, the body's first defense is inflammation.

Fever enhances the body's defense mechanisms. Blood is moved into the interior of the body, to reduce heat loss. Then, when heat regulating mechanisms return to normal, the body reduces its temperature by returning blood to the skin and perspiring. Chills may result.

In many cases, the body's own defense mechanisms are capable of repelling attacks by invading microorganisms, like bacteria and viruses. When the bacteria succeeds in multiplying to the point where the body's natural defenses are not adequate, antibiotics may be needed to either destroy the bacteria completely, or else kill enough of them so that the immune system can finish the job.