Ch.10: Antimicrobial Drugs

Question 1

What is the first practical antimicrobial agent discovered?

Answer 1

Sulfanilamide

Discovered by Gerhard Domagk in 1932.

Question 2

What is penicillin released from?

Answer 2

Penicillium

It creates a zone where bacteria cannot grow.

Question 3

What is the key to successful chemotherapy against a microbe?

Answer 3

Selective toxicity

It means being more toxic to the pathogen than to the host.

Question 4

What are the three types of antibiotics based on their production?

Answer 4

• Natural
• Semisynthetic
• Synthetic

Question 5

What do beta-lactams interfere with in bacteria?

Answer 5

Cross-linkage of NAM subunits

This leads to weakened cell walls and lysis.

Question 6

What is the function of vancomycin?

Answer 6

Natural antibiotic

It interferes with alanine-alanine bridges linking NAM subunits in Gram + bacteria.

Question 7

What is the mechanism of action for aminoglycosides?

Answer 7

Inhibit the 30S subunit of ribosomes

Examples include streptomycin and gentamicin.

Question 8

Fill in the blank: The type of ribosome found in prokaryotes is _______.

Answer 8

70S

Question 9

What is the role of sulfanilamide in metabolic inhibition?

Answer 9

It is a structural analog of PABA

It prevents the synthesis of folic acid needed for DNA and RNA.

Question 10

What do azoles inhibit in fungi?

Answer 10

Ergosterol synthesis

This leads to disruption of fungal cell membranes.

Question 11

What is the purpose of attachment antagonists?

Answer 11

Block viral attachment or receptor proteins

This is a new area of antimicrobial drug development.

Question 12

What is the ideal antimicrobial agent characterized by?

Answer 12

• Readily available
• Inexpensive
• Chemically stable
• Easily administered
• Nontoxic and nonallergenic
• Selectively toxic against a wide range of pathogens

Question 13

True or False: Antibiotics are effective against viruses.

Answer 13

False

Question 14

What are the two types of metabolic antagonists mentioned?

Answer 14

• Sulfonamides
• Trimethoprim

Question 15

What is the effect of polymyxins on bacteria?

Answer 15

Disrupt the plasma membrane

Effective against Gram negatives but toxic to human kidneys.

Question 16

What do nucleoside analogs do?

Answer 16

Block incorporation of standard nucleic acids

Typically used against viruses.

Question 17

How does bacitracin inhibit bacterial growth?

Answer 17

Blocks NAG-NAM transport out of the plasma membrane

It affects actively growing cells.

Question 18

What is the spectrum of action of an antimicrobial agent?

Answer 18

The number of different pathogens a drug acts against

It can be narrow or broad spectrum.

Question 19

What is the mechanism of action of rifampin?

Answer 19

Inhibit RNA polymerase

It specifically binds to prokaryotic RNA polymerase.

Question 20

Fill in the blank: The cell wall of fungi is composed of _______.

Answer 20

Polysaccharides not found in mammals

Question 21

What is the effect of chloramphenicol on ribosomes?

Answer 21

Blocks the enzyme site of the 50S ribosomal subunit

It prevents peptide bond formation.

Question 22

What is the role of protease inhibitors in antiviral therapy?

Answer 22

Interfere with an enzyme that HIV needs in its replication cycle

Question 23

What are natural, semisynthetic, and synthetic antibiotics?

Answer 23

Natural antibiotics come from microorganisms, semisynthetic are modified natural ones, and synthetic are man-made

Question 24

How do antibiotics affect bacterial cell walls?

Answer 24

Antibiotics like penicillin inhibit cell wall synthesis, causing bacterial lysis.

Question 25

How do antibiotics affect protein synthesis?

Answer 25

Antibiotics like tetracycline block bacterial ribosomes, halting protein production.

Question 26

How do antibiotics target bacterial membranes?

Answer 26

Polymyxins disrupt membrane integrity, causing leakage and cell death

Question 27

How do antibiotics affect metabolic pathways?

Answer 27

Sulfonamides block folic acid synthesis, disrupting DNA and protein production.

Question 28

How do antibiotics affect bacterial nucleic acids?

Answer 28

Quinolones inhibit DNA gyrase, while rifamycins block RNA polymerase.

Question 29

How do antifungal drugs work?

Answer 29

Azoles inhibit ergosterol synthesis, while polyenes bind to ergosterol, disrupting the membrane.

Question 30

How do antiviral drugs affect nucleic acids?

Answer 30

Drugs like acyclovir inhibit viral DNA or RNA polymerases, blocking replication.

Question 31

What is a narrow-spectrum antibiotic?

Answer 31

It targets a specific group of bacteria (e.g., penicillin for Gram-positive).

Question 32

What is a broad-spectrum antibiotic?

Answer 32

It targets a wide range of bacteria (e.g., tetracycline).

Question 33

What causes secondary infections from antibiotics?

Answer 33

Antibiotics kill normal flora, allowing opportunistic pathogens to grow.

Question 34

What is the MIC?

Answer 34

The MIC is the lowest concentration of antibiotic that inhibits bacterial growth.

Question 35

How does the Etest differ from the MIC?

Answer 35

The Etest uses a gradient strip to determine MIC, while the MIC is measured directly.

Question 36

What is the Kirby-Bauer test?

Answer 36

It measures antibiotic effectiveness by the zone of inhibition around antibiotic discs.

Question 37

What are the main routes of drug administration?

Answer 37

Oral, intravenous, intramuscular, topical, and inhalation.

Question 38

What are common side effects of antibiotics?

Answer 38

Allergic reactions, toxic effects, and disruption of normal flora.

Question 39

How do resistant microbes arise?

Answer 39

Through mutations, horizontal gene transfer, and selective pressure from antibiotics.

Question 40

What is the role of R plasmids?

Answer 40

R plasmids carry antibiotic resistance genes and can spread between bacteria.

Question 41

How do bacteria gain resistance by mutation?

Answer 41

Mutations alter target sites, making bacteria resistant to antibiotics.

Question 42

What are 7 ways bacteria gain resistance?

Answer 42

1) Mutations, 2) Enzyme production (e.g., β-lactamases), 3) Reduced permeability, 4) Efflux pumps, 5) Target modification, 6) Horizontal gene transfer, 7) Biofilm formation.