Question 1

Which of the following best explains why capsules appear as clear halos around bacterial cells after performing a capsule stain using Carbol Fuchsin and Albumin?

Accepted Answer

Capsules are non-ionic and do not bind with the cationic Carbol Fuchsin stain, resulting in a clear halo.

Question 2

A student prepares a capsule stain using Klebsiella pneumoniae. After staining, the cells appear pink with clear halos. What is the primary function of the capsule in this organism?

Accepted Answer

To increase pathogenicity by protecting against phagocytosis.

Question 3

Which of the following steps is critical to avoid destroying the capsule during the capsule staining procedure?

Accepted Answer

Gently heat fixing the slide for only 5 seconds.

Question 4

Why is Albumin (egg white) used in the capsule staining procedure?

Accepted Answer

It serves as both a fixative and a background medium, helping visualize the capsule.

Question 5

Which of the following bacteria is most likely to be found in the human oral cavity and is a significant contributor to tooth decay?

Accepted Answer

Streptococcus mutans

Question 6

A microbiologist observes a capsule stain under oil immersion and sees pink rods with clear halos. Which equation best represents the relationship between the observed field diameter ($$D$$), total magnification ($$M$$), and the actual field of view ($$F$$)?

Accepted Answer

$$F = \frac{D}{M}$$

Question 7

Which of the following statements about Enterobacter aerogenes is correct?

Accepted Answer

It is a Gram-negative, motile rod with peritrichous flagella, commonly found in soil and water.

Question 8

Which of the following best describes the metabolic characteristics of Klebsiella pneumoniae?

Accepted Answer

Facultative anaerobe with both respiratory and fermentative metabolism.

Question 9

A patient develops pneumonia after hospitalization. The causative agent is found to be a Gram-negative, capsulated rod. Which organism is most likely responsible?

Accepted Answer

Klebsiella pneumoniae

Question 10

During the capsule staining procedure, why is it important NOT to blot the slide after washing?

Accepted Answer

Blotting can remove the stained cells from the slide, disrupting the visualization of the capsule.

Question 11

Which of the following best explains why Streptococcus pneumoniae is more virulent when it produces a capsule?

Accepted Answer

The capsule protects the bacterium from phagocytosis by host immune cells.

Question 12

Which of the following is a correct step in preparing a capsule stain, as shown in the first image?

Accepted Answer

Holding the slide at a 45° angle and spreading the mixture across the junction of two slides.

Question 13

Which of the following best describes the appearance of Klebsiella pneumoniae after capsule staining, as shown in the second image?

Accepted Answer

Pink rods surrounded by clear halos against a pinkish background.

Question 14

Which of the following is a distinguishing feature of Enterobacter aerogenes compared to Klebsiella pneumoniae?

Accepted Answer

E. aerogenes is motile with peritrichous flagella, while K. pneumoniae is non-motile.

Question 15

Which of the following best describes the role of dextran produced by Streptococcus mutans?

Accepted Answer

Dextran is a sticky capsular material that aids in adherence to tooth surfaces.

Question 16

A microbiologist is comparing the capsule stains of Klebsiella pneumoniae, Enterobacter aerogenes, and Streptococcus mutans. Which of the following is a correct observation based on the images provided?

Accepted Answer

K. pneumoniae and E. aerogenes appear as rods with clear halos, while St. mutans appears as cocci with clear halos.

Capsule Staining and Capsule-Forming Bacteria: Laboratory Study Guide

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