Chapter 20

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Antimicrobial Drugs

Penicillin was considered a "miracle drug" for all of the following reasons EXCEPT

It was the first antibiotic

A drug that inhibits mitosis, such as griseofulvin, would be more effective against

Fungi

Most of the available antimicrobial agents are effective against

Bacteria

Antimicrobial peptides work by

Disrupting the plasma membrane

In what way are semisynthetic penicillins and natural penicillins alike?

Both are based on B-lactam

Which of the following antibiotics is NOT bactericidal?

Polyenes

Which one of the following does NOT belong with the others?
A. Bacitracin
B. Cephalosporin
C. Monobactam
D. Penicillin
E. Streptomycin

Streptomycin

The antibiotic tetracycline binds to the 30S subunit of the ribosome as shown in Figure 20.1. The effect is to

Prevent peptide bond formation

The antibiotic cycloheximide binds to the 60S subunit of the ribosome as shown in Figure 20.2. The effect is to

Prevent polypeptide elongation in eukaryotes

Which of these antimicrobial agents has the fewest side effects?

Penicillin

Which of the following drugs does NOT act by competitive inhibition?

Streptomycin

Which of the following methods of action would be bacteriostatic?

Inhibition of RNA synthesis

Which of the folllowing antibiotics is recommended for use against gram-negative bacteria?

Polymyxin

Which of the following antimicrobial agents is recommended for use against fungal infections?

Amphotericin B

In Table 20.1, the minimal bactericidal concentration of antibiotic X is

15 ug/ml

In Table 20.1, the minimal inhibitory concentration of antibiotic X is

10 ug/ml

More than half of our antibiotics are

Produced by bacteria

The antibiotic chloramphenicol binds to the 50S subunit of the ribosome as shown in Figure 20.3. The effect is to

Prevent attachment of tRNA

The antibiotic streptomycin binds to the 30S subunit of the ribosome as shown in Figure 20.4. The effect is to

Cause misreading of mRNA in 70S ribosomes

Which compound would be the most useful to treat candidasis?

Flucytosine

Which of the following antibiotics are used to treat fungal infections?
Aminoglycosides
Cephalosporins
Griseofulvin
Polyenes
Bacitracin

Griseofulvin
Polyenes

Which of the following antibiotics does NOT interfere with cell wall synthesis?

Macrolides

The antimicrobial drugs with the broadest spectrum of activity are

Tetracyclines

Which of the following statements is false?
A. Fluoroquinolone inhibits DNA synthesis
B. Acyclovir inhibits DNA synthesis
C. Amantadine inhibits release of viral nucleic acid
D. Interferon inhibits glycolysis
E. Azoles inhibit plasma membrane synthesis

Interferon inhibits glycolysis

Protozoan and helminthic diseases are difficult to treat because

Their cells are structurally and functionally similar to human cells

Which of the following organisms would most likely be sensitive to natural penicillin?

Streptococcus pyrogenes

Which of the following statements about drug resistance is false?

It is found only in gram-negative bacteria

Which of the following does NOT constitute an advantage of using two antibiotics together?

Two are always twice as effective as one

Drug resistance occurs

When antibiotics are used indiscriminantly

In Table 20.2, the most effective antibiotic tested was

10mm

In Table 20.2, the antibiotic that exhibited bactericidal action was

Can't tell

In Table 20.2, which antibiotic would be most useful for treating a Salmonella infection?

Can't tell

Which of the following would be selective against the tubercle bacillus?

Ethambutol - inhibits mycolic acid synthesis

In the presence of penicillin, a cell dies because

It undergoes osmotic lysis

Lamisil is an allylamine used to treat dermatomycoses. Lamisil's method of action is similar to that of

Azole antibiotics

Niclosamide prevents ATP generation in mitochondria. You would expect this drug to be effective against

Helminths

The data in Table 20.3 show that these bacteria

Developed resistance to antibiotics

Which of the following statements about drugs that competitively inhibit DNA polymerase or RNA polymerase is false?

They are too dangerous to use

The substrate for transpeptidase used to synthesize peptidoglycan is shown in Figure 20.5. Which of the drugs shown would inhibit peptidoglycan synthesis?

Horizontal beginning with hexagon

The structures of the influenza drug Tamiflu and sialic acid for influenza virus' neuramidase, are shown in Figure 20.6. What is the method of action of Tamiflu?

Competitive inhibition

Which of the following does NOT affect eukaryotic cells?

Semisynthetic penicillins

Mebendazole is used to treat cestode infections. It interferes with microtubule formation; therefore, it would NOT effect

Bacteria

Which of the following antibiotics causes misreading of mRNA?

Aminoglycoside

The antibiotic actinomycin D binds between adjacent G-C pairs, thus interfering with

Transcription

Use of antibiotics in aminal feed leads to antiobiotic-resistant bacteria because

The antibiotics kill susceptible bacteria, but the few that are naturally resistant live and reproduce, and their progeny repopulate the host animal

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