Question 1

The situation in which the effect of two antimcrobials given together is more effective than the effect of either medication given individually is referred to as

Accepted Answer

Synergism refers to the situation where two antimicrobials given together have a greater effect than the effect of either medication given individually. This can occur when the drugs have complementary mechanisms of action or when one drug enhances the activity of the other.

Question 2

Acyclovir is selective and low in toxicity, causing little harm to uninfected cells, because

Accepted Answer

Acyclovir is a nucleoside analog that requires viral thymidine kinase (a virally encoded enzyme) to convert it to an active form (nucleotide analog) that halts viral DNA replication. As uninfected cells do not have this enzyme, acyclovir only targets and harms the infected cells.

Question 3

Several diseases caused by herpesviruses are treated with a medication called acyclovir. This medication is a nucleoside analog, meaning

Accepted Answer

Acyclovir is a nucleoside analog, which means it mimics the structure of a nucleoside by containing a nucleotide analog (the base) and a sugar, but it does not contain a phosphate group, distinguishing it from a nucleotide.

Question 4

Azithromycin is a bacteriostatic antibiotic that interferes with protein synthesis. Ceftriaxone is a β-lactam antibiotic and is primarily bactericidal. This means that

Accepted Answer

Azithromycin is a bacteriostatic antibiotic, meaning it inhibits the growth of bacterial cells, while ceftriaxone is a bactericidal antibiotic, meaning it kills bacterial cells. Therefore, option C is the correct explanation.

Question 5

Antibiotics are effective in treating viral infections provided that they are given early in the course of illness.

Accepted Answer

Antibiotics are not effective in treating viral infections as they target bacteria, not viruses. Therefore, giving antibiotics early or late in the course of a viral infection will not have any effect on the virus itself.

Question 6

Viruses are completely unaffected by antibiotics because

Accepted Answer

Viruses are not affected by antibiotics because they lack the structures targeted by antibiotics, such as the cell wall and ribosomes. Additionally, they rely on the host cell's metabolic machinery for their replication, making it difficult to find a target for selective toxicity. Therefore, D is the correct option as it combines both explanations.

Question 7

Fluoroquinolones act by inhibiting DNA gyrase, an enzyme involved in DNA replication. Resistance to this antibiotic is most commonly by

Accepted Answer

Fluoroquinolones act by inhibiting DNA gyrase, and resistance to this antibiotic is most commonly due to a change in the DNA gyrase target, which is an example of acquired resistance. This means that the bacteria have developed a mutation or acquired a new gene that alters the target of the antibiotic, making it less effective.

Question 8

A nucleoside analog can be phosphorylated in vivo by a virally encoded or normal cellular enzyme to form a nucleotide analog-a chemical structurally similar to the building blocks of DNA and RNA. Nucleotide analogs interfere with

Accepted Answer

Nucleotide analogs, by interfering with the synthesis of viral nucleic acids, can prevent viral replication and thus reduce the viral load. Nucleotide analogs are incorporated into the growing viral DNA chain and cause premature termination of the chain, ultimately inhibiting viral replication.

Question 9

Acyclovir interferes with viral DNA replication. Other mechanisms of antiviral medications include all of the following EXCEPT

Accepted Answer

While antiviral medications can target a variety of different stages of the viral life cycle, they do not typically destroy viral ribosomes as an antiviral mechanism.

Question 10

Which of the following targets would you expect to be the most selective with respect to toxicity?

Accepted Answer

Peptidoglycan synthesis is a process unique to bacteria, making it a highly selective target for antibiotics with minimal toxicity to human cells, which lack peptidoglycan.

Quiz 20: Antimicrobial Medications