Final answer:
Listeria monocytogenes primarily uses fimbriae, with surface adhesins, to adhere to host cells. While flagella and pili are present in some bacteria, they play different roles, with flagella aiding in locomotion and pili in genetic exchange.
Step-by-step explanation:
Listeria monocytogenes, a pathogenic bacterium, has several mechanisms for adhering to host cells, one of which is through the use of fimbriae, which are hair-like protein bristles on the cell surface. Molecules called adhesins are found on the fimbriae and are crucial for the attachment of the bacterium to host cells. Flagella are another appendage but are mainly used for locomotion rather than adhesion.
While pili are similar in structure to fimbriae and are used to exchange genetic material during conjugation, it's the fimbriae that are primarily responsible for attachment to surfaces, including host cells. The capsule, another structure that aids in bacterial adhesion, is not primarily used by Listeria for this purpose.
Therefore, the correct answer to the question concerning the mechanism through which Listeria monocytogenes adheres to host cells is: Via fimbriae.