Antimicrobial Drugs Flashcards
What similar problems are enountered w/ antiviral, antifungal, antiprotozoan, and antihelminthic drugs?
- At the cellular level, fungus, protozoan, or helminth resemble the human cell much more closely than a bacterial cell does.
- Viral infections are particularly difficult to treat b/c the pathogen is w/i the human host’s cells
What is the primary factor involved in the selective toxicity of antibacterial action in Gram (-) bacteria?
- The primary factor lies in the LPS outer layer of Gram (-) bacteria & the porins that form water-filled channels across this layer.
(2. Drugs that pass thr. the porin channels must be relatively SMALL and HYDROPHILIC. )
When the identity of the pathogen is not known, does a Broad-Spec. drug or Narrow-Spec. drug work better? What is the disadvantage/side-effect administrating such drug? Give an example
- A broad-spec. drug would have an advantage in treating a disease by saving valuable time
- Disadvantage:
a. Many normal microbiota of the host can also be destroyed
b. If some of the normal microbiota are not destroyed, while the pathogenic ones are, the normal microbiota can become opportunistic pathogens - Example: Candida albicans
List the 5 modes of action of antimicrobial drugs
- Inhibitors of Cell Wall Synthesis
- Inhibitors of Protein Synthesis
- Inhibitors of Nucleic Acid Synthesis
- Injuries to Plasma Membrane
- Inhibiting the Synthesis of Essential Metabolites
Inhibition of Cell Wall Synthesis:
a. Name the type of drug
b. How does inhibition work?
c. Any adverse effects on human?
a. Penicillin
b. Inhibit synthesis of intact Peptidoglycan; consequently, the cell wall is greatly weakened and the cell undergoes lysis
Inhibition of Cell Wall Synthesis:
a. List the drugs
b. How does inhibition work?
c. Any adverse effects on human?
a. Penicillins, Cephalosporins, Bacitracin, Vancomycin, etc
b. Penicillins inhibit synthesis of intact Peptidoglycan; consequently, the cell wall is greatly weakened and the cell undergoes lysis
Inhibition of Protein synthesis
a. List the drugs
b. What is the mechanism?
c. Any adverse effects on human?
a. Chloramphenicol, Erythromycin, Tetracyclines, Streptomycin
b. Pro. cells have 70S ribosomes (50S & 30S)
1. Antibiotics that target the 50S subunit:
- - Chloramphenicol: inhibits the formation of peptide bonds in the growing polypeptide chain
- - Erythromycin:
1. Antibiotics that target the 30S subunit:
- - Tetracyclines: interfere w/ the attachment of the rRNA carrying the AAs to the ribosome
c. Though Euk. cells have 80S ribosomes, mitochondria also contain 70S ribosomes. So antibiotics targeting pro. ribosomes will also target mitochondrial ribosomes.
Chloramphenicol
a. Mode of action
b. Mechanism
a. Inhibit protein synthesis
b. Binds to 50S portion and inhibits formation of peptide bond
Erythromycin
a. Mode of action
b. Mechanism
a. Inhibit protein synthesis
b. Binds to 50S portion and prevents translocation-movement of ribosome along mRNA
Tetracycline
a. Mode of action
b. Mechanism
a. Inhibit protein synthesis
b. Interfere w/ attachment of tRNA to mRNA-ribosome complex
Streptomycin
a. Mode of action
b. Mechanism
a. Inhibit protein synthesis
b. Changes shape of 30S portion, causes code on mRNA to be read incorrectly
Inhibition of Protein synthesis
a. List the drugs
b. What is the mechanism?
c. Any adverse effects on human?
a. Chloramphenicol, Erythromycin, Tetracyclines, Streptomycin (Gentamycin)
b. Pro. cells have 70S ribosomes (50S & 30S)
1. Antibiotics that target the 50S subunit:
- - Chloramphenicol: inhibits the formation of peptide bonds in the growing polypeptide chain
- - Erythromycin:
1. Antibiotics that target the 30S subunit:
- - Tetracyclines: interfere w/ the attachment of the rRNA carrying the AAs to the ribosome
c. Though Euk. cells have 80S ribosomes, mitochondria also contain 70S ribosomes. So antibiotics targeting pro. ribosomes will also target mitochondrial ribosomes.
Chloramphenicol
a. Mode of action
b. Mechanism
c. Any adverse effects on human
a. Inhibit protein synthesis
b. Binds to 50S portion and inhibits formation of peptide bond
c. Chloramphenicol can suppress bone marrow activity, thus, affecting the formation of blood cells
Injury to the Plasma Mem.
a. List the drugs
b. What is the mechanism?
c. Any adverse effects on human?
a. Polymyxin B, Amphotericin B, Miconazole, Ketoconazole
b. Causes diruption of the plasma mem. by attaching to the phospholipids of the mem.
c. Plasma mem. of animal cells contain sterols, and amphotericin B and ketoconazole can be toxic to the host
- - Bacterial plasma mem. generally lack sterols, so these antibiotics do not work on bacteria.
Amphotericin B
a. Mode of action
b. Mechanism
a. Injury to the Plasma mem (antifungal)
b. Combine with sterols in the fungal plasma mem. to disrupt the mem.