Question 1

Which of the following statements best explains why it is difficult to achieve selective toxicity when treating viral infections?

Accepted Answer

Viruses use host cell machinery for replication, so drugs that target viruses often harm host cells as well.

Question 2

Which of the following is a correct description of the lytic cycle in bacteriophage replication?

Accepted Answer

The phage injects its DNA, takes over the host machinery, produces new phages, and lyses the host cell to release progeny.

Question 3

Which of the following best describes the function of the viral envelope?

Accepted Answer

It helps the virus attach to and enter host cells by fusing with the host membrane.

Question 4

A patient is prescribed a drug that inhibits peptidoglycan synthesis in bacteria. Which class of drugs is this most likely to be?

Accepted Answer

Beta-lactam antibiotics such as penicillins or cephalosporins

Question 5

Which of the following is the correct order of the stages of an infectious disease?

Accepted Answer

Incubation period, prodromal period, period of illness, period of decline, period of convalescence

Question 6

Which of the following best explains why moist heat is more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins more rapidly due to better heat transfer, requiring less time to achieve sterilization.

Question 7

Which of the following is a correct statement about prions?

Accepted Answer

Prions are infectious proteins that cause spongiform encephalopathies by inducing abnormal folding of host proteins.

Question 8

A hospital patient develops a urinary tract infection after catheterization. This infection is best classified as:

Accepted Answer

A nosocomial infection

Question 9

Which of the following best describes the mechanism of action of aminoglycoside antibiotics?

Accepted Answer

They bind to the 30S ribosomal subunit, causing misreading of mRNA and production of faulty proteins.

Question 10

Which of the following is the best explanation for why antifungal drugs often have significant side effects in humans?

Accepted Answer

Fungal cells are eukaryotic and share many cellular structures with human cells, making selective toxicity difficult.

Question 11

Which of the following is a correct statement about the minimum inhibitory concentration (MIC) in antimicrobial drug testing?

Accepted Answer

It is the lowest concentration of a drug that prevents visible growth of a microorganism.

Question 12

A patient is prescribed a combination of two antibiotics that work better together than alone. This is an example of:

Accepted Answer

Synergism

Question 13

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

Accepted Answer

They act as competitive inhibitors of the enzyme involved in folic acid synthesis, blocking the production of folic acid in bacteria.

Question 14

Which of the following is the most resistant to deactivation by physical and chemical agents?

Accepted Answer

Prions

Question 15

Which of the following best describes the difference between an exotoxin and an endotoxin?

Accepted Answer

Exotoxins are secreted proteins with specific targets, while endotoxins are lipopolysaccharides released from the outer membrane of Gram-negative bacteria.

Question 16

A virus that can only infect certain types of cells in a specific host demonstrates which property?

Accepted Answer

Host range and specificity

Question 17

Which of the following is a correct statement about the therapeutic index (TI) of an antimicrobial drug?

Accepted Answer

A high TI means the drug is safer, as the toxic dose is much higher than the effective dose: $$TI = \frac{	ext{Toxic Dose}}{	ext{Effective Dose}}$$

Question 18

Which of the following is an example of a mechanical method of microbial control?

Accepted Answer

Filtration using a HEPA filter

Question 19

Which of the following best describes the action of antiherpes drugs such as acyclovir?

Accepted Answer

They are nucleotide analogs that compete for sites on replicating DNA, inhibiting viral DNA synthesis.

Question 20

Which of the following is a correct statement about normal flora (microbiota)?

Accepted Answer

Normal flora can prevent colonization by pathogens through microbial antagonism.

Microbiology Exam 3 Study Guide: Viruses, Microbial Control, Antimicrobial Drugs, Infectious Disease, and Microbial Groups

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