PATHOGENESIS

The pathogenesis of bacterial infection includes the initiation of the infectious process and the mechanisms leading to the development of signs and symptoms of bacterial disease.

The outcome of the interaction between bacteria and host is determined by characteristics that favour establishment of the bacteria within the host and their ability to damage the host as they are opposed by host defense mechanisms
Among the characterics of bacteria are adherence to host cells, invasiveness, toxigenity, and ability to evade the host´s immune system.

If the bacteria or immunological reactions injure the host sufficiently, disease becomes apparent.

Humans and animals have abundant normal microflora.

Most bacteria do not produce disease but achieve a balance with the host that ensures the survival, growth, and propagation of both the bacteria and the host.

Sometimes bacteria that are clearly pathogens (e.g. Salmonella typhi) are present, but infection remains latent or subclinical and the host is a "carrier" of the bacteria.