The process by which bacteria cause disease is known as bacterial pathogenesis. Pathogenesis is influenced by a number of factors in both the bacteria and the individual host, and it can change at any time due to environmental pressures and other factors. Bacterial pathogenesis research is important because it demonstrates to medical and scientific communities how bacteria cause disease and how this process can be disrupted to prevent or treat illness.
Several factors influence the success of bacterial invasions in the host. The first is the immune system’s health, which influences resistance and susceptibility. Other factors can include the host’s living environment; for example, someone who does not have access to clean water is susceptible to re-infection with the same bacteria, whereas someone who is only exposed in passing is not. Access to medical treatment can also play a role in determining when and how aggressively intervention is carried out.
Only a small percentage of bacteria actually cause disease. Many more are unfavorable, and some are even harmful. To cause disease, bacteria must be capable of either triggering disease-causing reactions in the body or releasing their own toxins to cause illness. The bacteria must also be able to grow quickly enough to get past the immune system’s defenses, as well as be infectious. Bacteria frequently complete multiple life cycles within the body, and in some cases, they even use the body to reproduce.
Colonization is the first step in the bacterial pathogenesis process, in which bacteria settle on or in the body and begin to multiply before spreading. As the bacteria spread, they may release toxins that make the host sick, or they may take over the host’s body and trigger a chain reaction. The immune system, for example, may go into overdrive and begin attacking tissues in the host’s body. The host will become ill if the bacteria is able to penetrate and spread.
In some cases, the host’s own body can stop bacterial pathogenesis by fighting back against the bacteria. While the body is at work, the host may feel a little sick, but he or she will not become infected. In other cases, antibiotics and other treatments are required to manage and combat the infection. Once bacteria have colonized a host, the interaction between the bacteria and the host can go in any number of directions; being able to identify and predict the direction of an infection is critical. The complex factors that collide during the course of a bacterial infection are studied by those who study bacterial pathogenesis.