Which of the following bacterial structures is involved in attachment to the cell surface?

WCL Staff Nurse - 2022

Applied Microbiology & Infection control

Easy

Appeared in: WCL Staff Nurse - 2022

Explanation

Fimbriae, also known as pili, are short, fine, hair-like appendages found on the surface of many bacteria.
Their primary function is to act as adhesins, allowing the bacteria to attach to specific receptors on the surface of host cells.
This attachment is a critical virulence factor, as it is the first step in the process of colonization and subsequent infection.
Examples include Neisseria gonorrhoeae using fimbriae to attach to urogenital epithelial cells and uropathogenic E. coli using them to adhere to the bladder lining.

Option A: Flagella are primarily responsible for motility (locomotion), not attachment. They are long, whip-like structures that propel the bacterium through its environment.
Option C: The capsule is a polysaccharide or polypeptide layer that primarily serves a protective role, shielding the bacterium from phagocytosis by host immune cells. While it can aid in biofilm formation which involves adherence to surfaces, its main role is not specific attachment to host cells.
Option D: Mesosomes are invaginations of the bacterial plasma membrane. They were once thought to be involved in processes like cell division or respiration, but are now largely considered to be artifacts created during the chemical preparation of samples for electron microscopy. They have no established physiological function.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Bacterial structures and their functions, specifically related to virulence and infection as background academic context rather than a clinical decision trigger.
Understanding bacterial attachment is crucial for preventing infections. Many hospital-acquired infections, such as Catheter-Associated Urinary Tract Infections (CAUTIs), occur because bacteria use fimbriae to adhere to medical devices and then colonize the patient.
Nursing interventions like maintaining a closed urinary drainage system, ensuring aseptic catheter insertion, and performing regular meatal hygiene are designed to minimize bacterial attachment and biofilm formation.
What if? If a bacterium lacked fimbriae but had a thick capsule and flagella, it would be motile and well-protected from phagocytosis, but it would be significantly less effective at causing infections that require initial attachment to mucosal surfaces, like a UTI.

How to Approach the Question

First, identify the key action in the question: 'attachment to the cell surface'.
Next, review the options, which are all bacterial structures.
Recall the primary function of each structure. Fimbriae (or pili) are specifically known as organs of adhesion.
Evaluate the other options: Flagella are for movement, the capsule is for protection, and mesosomes are artifacts.
Conclude that fimbriae are the structures responsible for attachment, making it the correct answer.

Concept Tested & Keywords

Concept Tested: Bacterial structures and their functions, specifically related to virulence and infection.
Stem keywords: bacterial structures, attachment, cell surface
Lead-in keywords: Which

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