All of the following are used by bacteria to attach to host cells except:

• A. Flagella
• B. Adhesins
• C. Fimbriae
• D. Capsules

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the role of bacterial structures in attachment to host cells. Bacteria use specific surface components to adhere to host tissues, which is crucial for colonization and infection.
2. Step 2: Review the functions of each listed structure: Adhesins are molecules that specifically bind to host cell receptors; Fimbriae (or pili) are hair-like appendages that facilitate attachment; Capsules are polysaccharide layers that can help in adherence and protection.
3. Step 3: Consider the function of flagella. Flagella primarily provide motility, allowing bacteria to move toward favorable environments, but they are not primarily involved in attachment to host cells.
4. Step 4: Compare the roles and identify which structure does not contribute to attachment. Since flagella are mainly for movement, they are the exception among the options given.
5. Step 5: Conclude that the correct answer is flagella because it is not used by bacteria to attach to host cells, unlike adhesins, fimbriae, and capsules.