Question 1

A hospital is experiencing an outbreak of a bacterial infection. The laboratory identifies the bacteria as Gram-negative, catalase-positive, and oxidase-positive. Which of the following tests would be LEAST useful in further differentiating this organism from other Gram-negative bacteria?

Accepted Answer

DNase test

Question 2

A culture of bacteria is started with 100 cells. If the population doubles every 30 minutes, how many cells will there be after 2 hours? Use the formula $$N_t = N_0$ (2^n)$$, where $$n is $$the number of generations.

Accepted Answer

1,600

Question 3

Which of the following statements best explains why Gram-negative bacteria are generally more resistant to disinfectants than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane containing lipopolysaccharide (LPS).

Question 4

A patient with a wound infection is treated with an antibiotic that inhibits protein synthesis at the 30S ribosomal subunit. Which class of antibiotic is most likely being used?

Accepted Answer

Aminoglycosides

Question 5

Which of the following best describes a chemoorganoheterotroph?

Accepted Answer

Uses organic chemicals as both energy and carbon sources

Question 6

A microbiologist is attempting to sterilize a heat-sensitive vitamin solution. Which method is most appropriate?

Accepted Answer

Filtration using a membrane filter

Question 7

Which of the following statements about endospores is TRUE?

Accepted Answer

Endospores are highly resistant to heat, desiccation, and chemicals.

Question 8

A disinfectant has a D-value ($$D_{80^\circ C}) of 2 $$minutes. If you start with $$10^6$$ bacteria, how long will it take to reduce the population to $$10^2$$ bacteria at 80$$^\circC$$?

Accepted Answer

8 minutes

Question 9

Which of the following best explains why maggot (larval) therapy is effective in treating chronic wounds?

Accepted Answer

Maggots secrete antibiotic molecules and physically remove bacteria by ingestion.

Question 10

Which of the following is a correct pairing of microbial nutritional category and example organism?

Accepted Answer

Chemoorganoheterotroph – Staphylococcus aureus

Question 11

A bacterium that grows optimally at pH 3 and can survive in environments with high sugar concentrations is best described as:

Accepted Answer

Acidophile and osmophile

Question 12

Which of the following statements about horizontal gene transfer is CORRECT?

Accepted Answer

Conjugation requires direct cell-to-cell contact.

Question 13

A new disinfectant is tested and found to have a Z-value of 10$$^\circC. $$What does this mean?

Accepted Answer

An increase in temperature of 10$$^\circC $$reduces the D-value by a factor of 10.

Question 14

Which of the following best describes the action of sulfa drugs?

Accepted Answer

They are growth factor analogs that block folic acid synthesis.

Question 15

A patient is infected with a virus. Which of the following antiviral agents is most likely to inhibit viral nucleic acid replication?

Accepted Answer

Nucleotide analogs

Question 16

Which of the following is a correct statement about the stationary phase of bacterial growth?

Accepted Answer

Nutrient depletion and waste accumulation halt population growth.

Question 17

Which of the following best explains why iron is an essential micronutrient for many bacteria?

Accepted Answer

It is a key component in cellular respiration and electron transport.

Question 18

A bacterium is described as a facultative aerobe. Which of the following best describes its oxygen requirements?

Accepted Answer

It grows better with oxygen but can survive without it.

Question 19

Which of the following is the most resistant to antimicrobial agents?

Accepted Answer

Prions

Question 20

A patient is prescribed an antifungal agent that inhibits ergosterol biosynthesis. Which class of drugs is this?

Accepted Answer

Azoles

Microbial Structure, Growth, and Control: Comprehensive Study Notes

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