Final answer:
The first step in the pathogenesis of typhoid fever is the invasion of the intestinal mucosa by Salmonella enterica serovar Typhi, which leads to internal tissue damage and onset of symptoms. Hence, the correct answer is option (B).
Step-by-step explanation:
The first step in the pathogenesis of typhoid fever is B) Invasion of the intestinal mucosa. The causative agent of typhoid fever, Salmonella enterica serovar Typhi, enters the body through the digestive tract, typically through contaminated food or water. Once inside the host, this bacteria adheres to the intestinal mucosa, marking the initial stage of infection.
This initial invasion interrupts the normal functioning of the intestine and allows for further bacteria dissemination into local tissues and, subsequently, the bloodstream.
In typhoid fever's case, extensive tissue involvement occurs as the bacteria devastate the body's local tissues, initiating the onset of symptoms such as high fever, body aches, and potential intestinal hemorrhage.
Learn more about Typhoid Fever Pathogenesis