Question 1

Which of the following best describes the purpose of the Kirby-Bauer method in microbiology?

Accepted Answer

To assess the susceptibility of bacteria to various antibiotics by measuring zones of inhibition.

Question 2

Which parameter is NOT required for standardization in the Kirby-Bauer disc diffusion assay?

Accepted Answer

The use of a nutrient broth with high glucose concentration.

Question 3

A bacterium is considered resistant to an antibiotic in the Kirby-Bauer test if:

Accepted Answer

There is no visible zone of inhibition around the antibiotic disc.

Question 4

Which of the following best distinguishes a bacteriostatic antibiotic from a bactericidal antibiotic?

Accepted Answer

Bacteriostatic antibiotics inhibit bacterial growth, while bactericidal antibiotics kill bacteria.

Question 5

If two antibiotics are synergistic, what would you expect to observe in a disc diffusion assay?

Accepted Answer

The combined zone of inhibition is larger than the sum of the individual zones.

Question 6

What is the minimum inhibitory concentration (MIC) of an antibiotic?

Accepted Answer

The lowest concentration of antibiotic that prevents visible bacterial growth.

Question 7

In a serial dilution MIC assay, you observe no growth in tubes with $8$ and $16$ $\mu$g/mL antibiotic, but growth in the $4$ $\mu$g/mL tube. What is the MIC?

Accepted Answer

$8$ $\mu$g/mL

Question 8

Which of the following best describes the difference between MIC and MBC?

Accepted Answer

MIC is the lowest concentration that inhibits visible growth, while MBC is the lowest concentration that kills $99.9\%$ of the original inoculum.

Question 9

Which type of mutation is most commonly caused by UV radiation in bacterial DNA?

Accepted Answer

Thymine dimer formation.

Question 10

Why are spore-forming bacteria more resistant to UV radiation than non-spore-formers?

Accepted Answer

Spores have a thick protein coat that protects DNA from UV damage.

Question 11

Which of the following is a correct sequence for the steps of biofilm formation?

Accepted Answer

Attachment, irreversible attachment, maturation, dispersion.

Question 12

Which statement best distinguishes disinfectants from antiseptics?

Accepted Answer

Disinfectants are used on inanimate objects, while antiseptics are safe for use on living tissue.

Question 13

Which type of horizontal gene transfer is most likely to occur within a biofilm?

Accepted Answer

Conjugation

Question 14

What is a 'persister' cell in the context of biofilms?

Accepted Answer

A dormant cell within a biofilm that is tolerant to antibiotics.

Question 15

Which of the following is an example of horizontal gene transfer in bacteria?

Accepted Answer

Conjugation

Question 16

What is the F factor in bacterial conjugation?

Accepted Answer

A plasmid that carries genes for pilus formation and DNA transfer.

Question 17

In a transformation experiment using pGlo plasmid, which ingredient in the agar plate is essential for GFP expression?

Accepted Answer

Arabinose

Question 18

Which of the following is a real-life consequence of incorrectly identifying a bacterial pathogen in a clinical setting?

Accepted Answer

The patient may receive an ineffective or harmful treatment.

Question 19

How can you ensure that your bacterial culture remains pure during an experiment?

Accepted Answer

By using aseptic technique and regularly streaking for isolation.

Question 20

A student observes that two strains of the same bacterial species give different results in a Gram stain. What is the most likely explanation?

Accepted Answer

Different strains may have variations in cell wall structure affecting stain retention.

BIO221 Lab Material Review: Antimicrobial Methods, Biofilms, and Bacterial Genetics

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