Final answer:
Bacterial pathogens must go through exposure, adhesion, invasion, and infection stages to cause disease. They adhere to host tissues using adhesion factors and damage tissues with toxins and virulence factors. Diseases can be transmitted to new hosts, completing the cycle of infection.
Step-by-step explanation:
In order to cause disease, bacterial pathogens must successfully complete several stages of pathogenesis, which include exposure, adhesion (colonization), invasion, and infection. Pathogens need to gain entry to the host through portals of entry such as mucous membranes and broken skin, after which they adhere to host tissues with the help of adhesion factors. Following adhesion, they can then invade and multiply within host tissues, often producing toxins and virulence factors that can lead to disease. Damage to host tissues and an inflammatory response signify that infection has occurred. Finally, the disease can be transmitted to a new host, completing the infectious cycle.
Some pathogens are known for entering and multiplying within host cells, whereas others remain and multiply in body fluids. The extent of a pathogen's spread within the body can categorize infections as local, focal, or systemic. Additionally, a compromised immune system or microbiota can lead to secondary infections. It is also essential for pathogens to leave the host through portals of exit to continue their life cycle.