Microbial pathogenesis is the process by which a microorganism causes a disease. Microorganisms capable of microbial pathogenesis include bacteria, fungi and viruses. Forms of these organisms that cause diseases are called pathogens. Microbial pathogenesis tracks the origin and cause of the disease, how it manifests itself in the body and how the body reacts to it.
There are four main types of pathogenesis in the human body. Inflammation is the swelling of tissue in the body as a problem is dealt with and infected tissue is replaced. Malignancy is the abnormal development of cell reproduction as often found in cancers. Tissue breakdown or necrosis is the death of cells outside the normal cellular cycle. Infection occurs when cells are infected by bacteria, viruses of fungi spores.
Infections are the most likely form of microbial pathogenesis, though inflammations may occur as a byproduct of the infection. Any such infection can be divided into three broad categories. An acute infection is relatively short, finite and with a rapid onset. A chronic infection is longer-lasting and is difficult to deal with. A recurrent infection may have a rapid or slow onset, but will disappear as if healed only to come back at a later date.
Each infection through microbial pathogenesis takes place in three broad stages. These are the initial infection, reproduction and species continuation. The latter two are the main reasons for any infection. The microorganism requires a larger organism such as a human in order to multiply and spread itself. Multiplication or replication often takes place within a cell.
The objective for the microorganism once it has begun to replicate itself is to get versions of itself out of the body before the body’s self-defense forces destroy it. The body typically responds using a mixture of white blood cells, also called macrophages, and antibodies. The microorganism will, therefore, attempt to get out of the body in order to infect someone whose immune system is not set up to repel it instantly.
This means the initial phase of infection and the final phase of transmission are indelibly linked — there are four main ways for microbial pathogenesis to transmit from one person to another. The first is through aerosols such as water droplets in coughs and sneezes. The second is through ingestion or through fecal matter. The third is vector-borne, as in carried by other animals such as mosquitoes and ticks. The fourth main route is through the exchange of bodily fluids during sex, blood transfusions and kissing.
The success of the infection depends on many factors as well. The nature of the microorganism and how it replicates is one factor. Another is the immune status of the individual being infected. If the individual has had contact with the microorganism before, chances are the body will be well prepared to repel it.