Antibacterial Agents: Introduction Flashcards Preview

D&D Unit 3 > Antibacterial Agents: Introduction > Flashcards

Flashcards in Antibacterial Agents: Introduction Deck (14):
1

Define selective toxicity. Give examples

a

2

Define antibiotic spectrum (ie: narrow, extended, broad). Give examples

a

3

Define resistance (ie: natural, escape, acquired)

a

4

What are 4 biochemical differences between the pathogen target and the host which are then exploited by antibacterial agents?

1) Inhibiting metabolic pathways found in bacteria, not humans
2) Similar pathway in humans/bacteria, but have different enzyme structures
3) Macromolecular structure does not exist in human
4) Macromolecular structure differs between microbes and humans

5

What is an example of how inhibiting metabolic pathways found in bacteria, not humans, are exploited by antimicrobial agents

Folate metabolism:
Bacteria must create folate intracellularly ---- mammalian cells get folate from environment

6

What is an example of how similar pathways in humans/bacteria, but have different enzyme structures are exploited by antimicrobial agents?

Protein synthesis:
- Bacterial ribosomes and mammalian ribosomes are different

Nucleic acid synthesis:
- DNA gyrase (bacteria) vs topoisomerase (humans)
- RNA polymerase structurally distinct in bacteria

7

What is an example of a macromolecular structure that does not exists in humans that is exploited by antimicrobial agents?

Cell wall synthesis:
- Peptidoglycan does not exist in eukaryotes!

8

What is an example of a macromolecular structure that different between microbes and humans that is exploited by antimicrobial agents?

Fungal cell membrane:
- Ergosterol ---> major part of fungal membranes
- Whereas cholesterol ---> in mammalian membranes

9

Describe natural (intrinsic) resistance

- Microbes lack a susceptible target for drug action

Eg:
- Fungal cell walls ---> no peptidoglycan
- Mycoplasma ---> no cell walls
- Pseudomonas ---> drug cannot penetrate outer membrane

10

Describe the escape mode of resistance

Microbes are sensitive and antibiotics reach target BUT...
1) organism escapes b/c of precursor availability
2) Failure to lyse (no osmotic pressure difference)
3) Emphasizes important role for surgical drainage

11

What is acquired resistance? What are the two modes of acquired resistance?

Selective pressures produces successive generations of organisms w/ biochem traits that minimize drug action

1) Mutational (chromosomal) resistance
2) Plasmid mediated resistance

12

Describe mutational (chromosomal) resistance

- Multiple steps must occur for appreciable resistance
- Proper dosing and duration of antibiotic therapy can prevent this

13

Describe plasma mediated resistance

- Can emerge during a single course of treatment ****REALLY IMPORTANT****
- Can code for resistance to multiple drugs (MDR gene)

Resistance occurs through:
1) Conjugation
2) Transduction
3) Transformation

14

What are the major mechanisms of bacterial resistance to antibiotics?

1) Altered targets
2) Enzymatic destruction
3) Alternative resistant metabolic pathway
4) Decreased entry