Question 1

A patient is diagnosed with a bacterial infection. The physician prescribes an antibiotic that targets cell wall synthesis. Which of the following drugs is most likely prescribed, and what is the main reason this drug is selectively toxic to bacteria?

Accepted Answer

Penicillin; it targets peptidoglycan, which is unique to bacterial cell walls.

Question 2

A microbiologist is culturing a bacterium that grows best at 10°C and can survive in high salt concentrations. Which terms best describe this organism?

Accepted Answer

Psychrophile and halophile

Question 3

During which phase of the bacterial growth curve are cells most susceptible to antibiotics that target cell wall synthesis, and why?

Accepted Answer

Exponential (log) phase; because cells are actively dividing and synthesizing new cell walls.

Question 4

A laboratory technician needs to sterilize a solution that cannot be heated. Which method is most appropriate?

Accepted Answer

Filtration through a membrane filter

Question 5

Which of the following statements about the resistance of microorganisms to destruction is correct?

Accepted Answer

Endospores are the most resistant form of microbial life.

Question 6

A new antimicrobial drug has a toxic dose of $$200\ \mathrm{mg}$$ and a therapeutic dose of $$20\ \mathrm{mg}. $$What is its therapeutic index (TI), and what does this value indicate about the drug's safety?

Accepted Answer

$$TI = \frac{200}{20} = 10$$; the drug is relatively safe.

Question 7

Which of the following best explains why antibiotics are ineffective against viral infections?

Accepted Answer

Viruses use host cell machinery and lack the structures targeted by antibiotics.

Question 8

A culture of Staphylococcus epidermidis is able to grow in 10% salt at 37°C and can grow with or without oxygen. Which terms best describe this organism?

Accepted Answer

Halophile, mesophile, facultative anaerobe

Question 9

Which of the following chemical agents is most appropriate for use as a surgical scrub and in mouthwash due to its broad-spectrum activity?

Accepted Answer

Chlorhexidine

Question 10

A microbiologist observes bacterial growth only at the bottom of a thioglycollate broth tube. Which oxygen classification best describes this organism?

Accepted Answer

Obligate anaerobe

Question 11

Which of the following best describes a chemoheterotroph?

Accepted Answer

Uses organic compounds as both carbon and energy sources.

Question 12

A hospital is concerned about the spread of Mycobacterium tuberculosis. Which of the following statements about chemical control is most accurate?

Accepted Answer

Mycobacterium is more resistant to chemical disinfectants than enveloped viruses.

Question 13

Which of the following is a correct statement about the use of antibiotics in animal agriculture?

Accepted Answer

It can contribute to the development of antibiotic resistance in human pathogens.

Question 14

A restaurant uses a process to reduce microbial numbers on dishes to safe public health levels. Which term best describes this process?

Accepted Answer

Sanitization

Question 15

Which of the following best explains why a higher therapeutic index (TI) is preferred in antimicrobial drugs?

Accepted Answer

A higher TI means there is a greater margin of safety between the effective and toxic doses.

Question 16

A patient is prescribed an antifungal drug for a yeast infection. Which class of drugs is most likely prescribed?

Accepted Answer

Azoles

Question 17

A scientist is studying an organism that requires increased CO$$_2$$ levels for optimal growth. What is the correct classification for this organism?

Accepted Answer

Capnophile

Question 18

Which of the following statements about freezing as a method of microbial control is correct?

Accepted Answer

Freezing is bacteriostatic and inhibits bacterial growth.

Question 19

A patient stops taking their prescribed antibiotics early, even though symptoms have improved. What is the most likely consequence of this action?

Accepted Answer

It increases the risk of developing antibiotic-resistant bacteria.

Question 20

Which of the following best describes the action of glutaraldehyde in microbial control?

Accepted Answer

It is a high-level disinfectant and chemical sterilant.

Microbial Nutrition, Growth, Control, and Antimicrobial Treatment Study Guide

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