Antimicrobial Drugs

Question 1

“Magic Bullet”

Answer 1

• A cure for all infectious disease
• Dr. Paul Ehrlich introduced a treatment for syphilis but did not fully work
• This opened the door to field of Chemotherapy where chemicals are used to treat microbial infections

Question 2

Antimicrobial Drugs: Antibactierals

Answer 2

• Substances that kill bacteria or stop their growth
• Target the cell wall synthesis or protein production

Ex. Penicillins

Question 3

Antimicrobial Drugs: Antifungals

Answer 3

• Treat fungal infections by targeting cell structures and inhibit growth or kill fungi

Question 4

Antimicrobial Drugs: Antihelminths:

Answer 4

• Used to treat parasites

Question 5

Antimicrobial Drugs: Antivirals

Answer 5

• Used to treat viral infections bu inhibiting viral replication
• Often targets specific stages of the viral cycle rather than killing the virus directly

Question 6

Narrow and Broad Spectrum of Antimicrobial Drugs

Answer 6

• Narrow: one specific type of microbe is targeted and killed. Disadvantages: longer treatment duration, resistance development,
• Broad: most microbes are targeted and killed. Disadvantage: promotes antibiotic resistance and disrupts the git microbiome which can lead to other infections

Question 7

Criteria for Drug Design:

Answer 7

1) Selectively Toxicity: the drug can kill only the microbe

2) Route of Administration: goes to the correct area of the body

2) Cost of Research / Making the Drug Affordable

3) Limit the Side Effects

4) Half-life/Shelf-life

5) Dosage

6) Limit the Development of Antimicrobial Resistance

Question 8

Mechanism of Antibacterials:

Answer 8

• Inhibition of cell wall synthesis
• Inhibition of protein synthesis
• Injury to the plasma membrane
• Inhibition of nucleic acid synthesis
• Inhibition of metabolism

Question 9

Beta-Lactam Antibiotic Drugs: Inhibition of cell wall synthesis

Answer 9

• Inhibit the synthesis of bacterial cell walls by binding to enzymes called Penicillin-binding proteins

Natural Penicillins: narrow and bacteriocidal. Ex. Penicillin G and V

Semisynthetic Penicillins: broad and bacteriocidal. Ex. Amoxicillin

Question 10

Vancomycin (Antibiotic Treatment)

Answer 10

Used to treat colitis (inflammation of the intestine caused by certain bacteria) that may occur after antibiotic treatment.

Question 11

Inhibition of protein synthesis:

Answer 11

Ex. Streptomycin (bacteriocidal and broad) - binds to 70s ribosomes and is permanent

Ex. Tetracycline (bacteriostatic and broad) - binds to 70s ribosomes and is temporary

• Not taken by mouth. Last chance drug.

For someone who has a chronic (long term), non-life threatening bacterial infection would use Tetracycline because its temp.

Question 12

Injury to Plasma Membrane:

Answer 12

Ex. Polymyxin B (bactericidal and broad)

• Not taken by mouth. Last chance drug.
• Interferes with fatty synthesis to help synthesize the plasma membrane

Question 13

Inhibition of Nucleic Acid Synthesis:

Answer 13

Ex. Rifampin (bactericidal and narrow) - inhibits the synthesis of mRNA by interfering with RNA polymerase

Ex. Ciprofloxacin (bactericidal and broad) - inhibits supercoiling of bacterial DNA by interfering DNA gyrase

Question 14

Inhibitions of Metabolism:

Answer 14

Ex. Sulfa Drugs with Trimethoprim (bacteriostatic and board)

• Sulfa drugs: synthetic antibiotics that inhibit bacterial growth by interfering with the synthesis of folic acid
• Trimethoprim: inhibits bacterial growth by blocking the production of folic acid
• Work better together. Enhances their effectiveness and allows them to target a broader spectrum of bacteria

Question 15

Four Ways to Antibiotic Resistance

Answer 15

1) Inactivation of the drug by enzymes: Gram +

2) Alter the drug’s target site: Gram +

3) Inhibition of drug uptake by a modified cell wall protein: Gram -

4) Ejection of drug (efflux pumps or multi-drug resistant pumps): Gram -

Question 16

Test the Effectiveness of an Antibiotic: Antibiotic Disk Diffusion

Answer 16

Ex. Kirby-Baur disk diffusion test

• Zones of inhibition form around the antibiotic disks if the drug is effective

– Smaller the zone = the more resistant the microbe is to the drug

– Bigger the zone = the more sensitive the microbe is to the drug

Question 17

Test the Effectiveness of an Antibiotic: Broth Dilution Test

Answer 17

Broth dilutions of an antibiotic in a liquid medium, inoculating it with bacteria and observing the growth

• the least amount of visible growth = the more sensitive the microbe is to the drug

Question 18

Antifungal Drugs

Answer 18

Miconazole and Amphotericin B:

• Both interfere with the plasma membrane of the fungal cell by targeting ergosterol.
• Doesn’t effect human cells because we have cholesterol in our plasma membranes.

Question 19

Antiprotozoan Drug

Answer 19

Flagyl: interferes with anaerobic metabolism in the protozoan

Question 20

Antiparasitic Drug

Answer 20

Ivermectin:
- interferes with glucose metabolism in the parasite