Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MICR2209 > 19 - Antibiotics Development and Mode of Action > Flashcards

19 - Antibiotics Development and Mode of Action Flashcards

1
Q

Physical agents

A

Heat, radiation (no to low selectivity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Chemical agents

A
  • Antiseptics, disinfectants (no to low selectivity)
  • Antibiotics, synthetic antimicrobials (moderate to high selectivity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Chemotherapy

A

The use of chemical agents to treat disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Broad spectrum antibiotics

A

Inhibits/kills a broad range of microbes (e.g. Tetracycline inhibits Gram-ve, Gram+ve, Chlamydia, Rickettsia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Narrow spectrum antibiotics

A
  • Inhibits/kills narrow range of microbes (e.g. only gram +’ve or only gram -‘ve)
  • specificity often due to the differences in their cell envelope structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Static agents

A
  • Growth is inhibited but no killing occurs
  • Upon removal of the agent the microbe will recover and resume growth
  • Bacteriostatic
  • E.g. Chloramphenicol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Cidal agents

A
  • Cidal agents result in irreversible microbe death, some cause cell lysis
  • Bactericidal
  • E.g. Penicillin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Toxic dose

A

Dose at which drug becomes too toxic for the host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

therapeutic dose

A

Dose needed to treat the infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Selective toxicity

A

kill or inhibit microbial pathogen but damage host as little as possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Therapeutic index

A
  • Toxic dose/Therapeutic dose
  • The larger the therapeutic index, the better the chemotherapeutic agent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Targets of antibiotic action

A
  1. Inhibitors of protein synthesis
  2. Inhibitors of cell wall synthesis
  3. Metabolic antagonists/antimetabolites
  4. Inhibitors of DNA/RNA synthesis
  5. Cell membrane disruption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are antibiotics usually relatively non toxic drugs

A

Targets of antibiotic action are different or nonexistent in eukaryotic cells (including
humans). E.g. presence of cell wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Selective toxicity of inhibitors of protein synthesis

A

Selective toxicity fairly good, as they target bacterial ribosomes, not eukaryotic ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Size of prokaryotic ribosomes

A

70S (50S + 30S subunit)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Size of eukaryotic ribosomes

A

80S (60S + 40S subunit)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Mechanism of action of aminoglycosides

A
  • Bind to 30S subunit of ribosome, cause misreading of genetic code
  • Cidal
  • Broad spectrum
  • E.g. Streptomycin
18
Q

Mechanism of action of tetracyclines

A
  • Bind to 30S subunit
  • Static
  • Broad spectrum
  • E.g. Tetracycline
19
Q

Mechanism of action of macrolides

A
  • Bind to 23S rRNA of 50S subunit
  • Static
  • Broad spectrum
  • E.g. Erythromycin
20
Q

Mechanism of action of chloramphenicol

A
  • Bind to 23S rRNA of 50S subunit
  • Static
  • Broad spectrum
  • E.g. Chloramphenicol
21
Q

Selective toxicity of inhibitors of cell wall synthesis

A

Selective toxicity excellent, as they target bacterial cell wall which is not present
in eukaryotic cells

22
Q

Mechanism of action of penicillins (β-lactams)

A
  • Inhibit transpeptidation enzymes (=penicillin-binding proteins) involved in cross-linking peptidoglycan cell wall
  • Cidal
  • Pencillin = Narrow spectrum
  • Ampicillin = Broad spectrum
23
Q

How does penicillin inhibit penicillin binding proteins

A
  • Penicillins contain β-lactam ring,
    which resembles the terminal D-alanyl-D-alanine of the peptides
  • Thus penicillins block cross-link formation
  • Growing cell wall becomes less able to resist osmotic pressure - penicillins lyse growing cells
24
Q

Limitations of penicillin

A
  • Natural penicillins produced by Penicillium fungus (penicillin G, penicillin V), active against Gram positives, have limitations
  • Pen G destroyed by stomach acid, somust be given by injection
  • Penicillin-resistance via penicillinases soon developed
  • Semisynthetic penicillins developed to overcome these limitations
25
Q

Semisynthetic penicillin

A
  • New side chains added to β-lactam ring
  • Advantages include broader spectrum of
    activity, acid stability so can be taken
    orally, resistance to some penicillinases
26
Q

Antibiotics that inhibit protein synthesis

A
  • aminoglycosides
  • tetracyclines
  • macrolides
  • chloramphenicol
27
Q

Antibiotics that inhibit cell wall synthesis

A
  • Penicillins
  • cephalosporins
  • vancomycin
28
Q

Mechanism of action of cephalosporins

A
  • contain β- lactam ring
  • Broad spectrum
  • Cidal
  • E.g. cephalothin
  • Useful if penicillin allergy
29
Q

Mechanism of action of vancomycin

A
  • Inhibits transpeptidation
  • Cidal
  • Narrow spectrum
  • E.g. Vancomycin
30
Q

What are metabolic antagonists/antimetabolites

A
  • Structurally similar to enzyme substrate, so compete with metabolite
  • Block enzyme activity, thus block a metabolic pathway
  • Can have good selective toxicity as host
    lacks pathway, or host enzyme differs from bacterial enzyme
31
Q

Antibiotics of metabolic antagonists/antimetabolites

A
  • sulfonamides
  • trimethoprim
32
Q

Mechanism of action of sulfonamides

A
  • inhibit folic acid synthesis by competing with PABA
  • Static
  • Broad spectrum
  • E.g. sulfanilamide
33
Q

Mechanism of action of trimethoprim

A
  • inhibits folic acid synthesis by inhibiting enzyme DHF reductase
  • Broad spectrum
  • Static
  • E.g. Trimethoprim
34
Q

Selective toxicity of inhibitors of nucleic acid synthesis

A

Poor selective toxicity because bacteria and eukaryotes have similar nucleic acid synthesis pathways

35
Q

Antibiotics that inhibit nucleic acid synthesis

A
  • Quinolones
  • Rifampin
36
Q

Mechanism of action of quinolones

A
  • inhibit DNA gyrase: block DNA replication
  • Cidal
  • Broad spectrum
  • E.g. Ciprofloxacin
37
Q

Mechanism of action of rifampin

A
  • Inhibits RNA polymerase: blocks RNA synthesis
  • Cidal
  • Narrow spectrum (TB, leprosy)
  • E.g. Rifampicin
38
Q

Selective toxicity of cell membrane disruptors

A

Poor selective toxicity as bacterial and human membranes are very similar in structure

39
Q

Antibiotics that disrupt cell membrane

A

Polymyxins

40
Q

Mechanism of action of polymyxins

A
  • Disrupt plasma membrane, detergent-like activity
  • Cidal
  • Narrow spectrum
  • E.g. Colistin

MICR2209 (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions