Question 1

A hospital is experiencing an outbreak of a bacterial infection. To prevent further spread, the staff must sterilize surgical instruments. Which method would be most effective for achieving sterilization, and why?

Accepted Answer

Using an autoclave at 121°C and 15 psi for 15 minutes, because it destroys all forms of microbial life including spores.

Question 2

During the log phase of a bacterial growth curve, the population doubles every 30 minutes. If you start with $$1 	imes 10^3$ cells, how many cells will there be after 2 hours?

Accepted Answer

$$1.6 	imes 10^4$ cells$

Question 3

Which of the following best describes the difference between disinfection and antisepsis?

Accepted Answer

Disinfection reduces microbes on inanimate surfaces, while antisepsis reduces microbes on living tissue.

Question 4

A patient is prescribed a broad-spectrum antibiotic. What is a potential risk associated with this treatment?

Accepted Answer

It can disrupt normal microbiota, increasing the risk of secondary infections such as Clostridioides difficile.

Question 5

Which environmental factor is most likely to limit the growth of an obligate aerobe in a sealed, oxygen-free container?

Accepted Answer

Absence of oxygen

Question 6

A laboratory technician uses a membrane filter with a pore size of $$0.2 \ \mu m to $$sterilize a solution. Which type of microorganism is most likely to pass through the filter and contaminate the solution?

Accepted Answer

Viruses

Question 7

Which of the following best explains why heat is an effective method for microbial control?

Accepted Answer

Heat denatures proteins and disrupts cell membranes, leading to cell death.

Question 8

A patient develops a bacterial infection that is resistant to multiple antibiotics. Which of the following mechanisms most likely contributed to the development of this resistance?

Accepted Answer

The bacteria acquired resistance genes through horizontal gene transfer from other bacteria.

Question 9

Which phase of the bacterial growth curve is characterized by a balance between cell division and cell death, resulting in a stable population size?

Accepted Answer

Stationary phase

Question 10

A microbiologist is testing the effectiveness of a new disinfectant. She applies it to a surface contaminated with $$1 	imes 10^6$ bacteria. After 10 minutes, only 1$$ 	imes $$10^3$$ bacteria remain. What is the log reduction achieved by the disinfectant?

Accepted Answer

$$3-log $$reduction$

Question 11

Which of the following best describes the mechanism of action for penicillin?

Accepted Answer

It inhibits cell wall synthesis by blocking peptidoglycan cross-linking.

Question 12

A culture medium contains glucose, peptone, and agar. Which component provides the primary carbon and energy source for most bacteria?

Accepted Answer

Glucose

Question 13

Why is the Kirby-Bauer disk diffusion test used in clinical microbiology laboratories?

Accepted Answer

To measure the effectiveness of antibiotics against specific bacteria by observing zones of inhibition.

Question 14

Which of the following is a real-world example of antisepsis?

Accepted Answer

Applying iodine to a patient’s skin before surgery.

Question 15

A bacterium is classified as a mesophile. At which temperature range would you expect it to grow best?

Accepted Answer

$$15-45^\circC$$

Question 16

Which of the following statements about microbial resistance is correct?

Accepted Answer

Overuse of antibiotics can select for resistant strains in a population.

Question 17

A patient with a urinary tract infection is treated with an antibiotic that inhibits protein synthesis. Which cellular structure is most likely targeted by this drug?

Accepted Answer

Ribosome

Question 18

Which of the following factors would NOT increase the effectiveness of a chemical disinfectant?

Accepted Answer

Shortening the time of exposure

Question 19

A microbiologist wants to measure the number of viable bacteria in a sample. Which method should she use?

Accepted Answer

Plate count method (serial dilution and colony counting)

Question 20

Which of the following best explains why some bacteria survive exposure to antibiotics and later cause recurrent infections?

Accepted Answer

Some bacteria possess resistance genes that allow them to survive and multiply after treatment.

Microbial Growth, Control, and Antimicrobial Therapy: Study Guide

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