Antibiotics & Antimicrobials Flashcards

1
Q

Define antibiotic

A

Substance produced by microorganisms or synthetically which posses the property of inhibiting the growth of or destroying other microoganisms

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

What is a bacteriostatic antibiotic? Give examples

A

Prevent the growth or reproduction of microorganisms in the host = leaving body’s natural defence mechanism to overcome infection
e.g. Tetracyclines, erthromycin, sulphonamides

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

What is a bacteriocidal antibiotic? Give examples

A

Inhibit the multiplication of the organisms but also kill bacteria even in the presence of pus

e.g. penicillin, streptomycin & cephalosporins

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

Give examples of broad spectrum antibiotics

A

Tetracycline, ampicillins and caphalosphorins (against gram +/- bacteria)

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

Give examples of narrow spectrum

A

Penicillin (gram +ve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Who accidentally discovered penicillin ?

A

Alexandra Flemming 1929

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Who first investigated, mass produced and sold penicillin?

A

Howard Florey & Ernist Chain 1940

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the uses of antibiotics in dentistry?

A
  1. Theraputic e.g. acute odontogenic infections that aren’t amenable by immediate dental tx
  2. Prophylaxis - prevention of distant infection or wound infection (e.g. risk to infetive endocarditis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When shouldn’t antibiotics be used in dentistry?

A
  • Inflammatory conditions (post op oedema)
  • Fibrinolytic conditions (e.g. dry sockets)
  • Non-bacterial condtions (e.g. viral/fungal infections)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is penicillin (beta-lactams) & glycopeptides more of action?

A

Interfere with cell wall synthesis: if cell wall is not intact = cell fragility & bacteriolysis = bacteriocidal

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

How are the cell walls in gram +/ gram - bacteria different?

A
  • Gram + have multple peptidoglycan layers in cell wall

- Gram - have a single layer of peptidoglycans.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a peptidoglycan?

A

-consists of chains of alternating amino sugars which are crosslinked via peptide side chains of N-acetylmuramic acid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the biosynthesis of bacterial peptidoglycan?

A
  • Glycan unit formed (from N-acetylmuramic acid, N-aceytlglucosamines & 5x amino acids)
  • Glycan unit is transported across cytoplasmic membrane & incorporated into the cell wall (by cell wall acceptors- transglycosylation)
  • Peptides from one layer join to another by peptide cross-links (transpeptidation) - enzymes involved transpeptidase also known as peniciliin binding sites (PBS)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does penicillin and cefalosporins work as an antimicrobial ?

A

Interferes with cell was synthesis

  • inhibits enzymes (PBS) responsible for cross linking between chains
  • inactivate autolysin inhibitors of bacteria thus autolysin is produced which creates defects in the cell wall by hydrolysing components
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the anitbacterial spectrum of cefalosporins?

A

Broad spectrum for gram +/- bacteria

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

Give an example of a glycopeptide?

A

Vancomycin

17
Q

How do glycopeptides interfere with cell wall synthesis?

A

-Prevent gylcan groups moving from cell membrane to cell wall=weakening cell wall

18
Q

What are glycopeptides used for?

A
  • Used to treat serious infections e.g. staphylococcal infections ( where the patient is allergic to penicillin
  • Clostridium difficile
  • Effective against aerobic /anaerobic gram +ve bacteria
19
Q

Which antimicrobials inhibit protein synthesis?

A
  • erythromycin
  • tetracycline
  • clindamycin
  • the aminoglycosides
  • fusidic acid
20
Q

What antimicrobials attach to the 30s subunit?

A

Tetracycline, streplomycin & gentamycin

21
Q

What anitmicrobials attach to the 50s subunit?

A

erythromycin & chlorampheniol

22
Q

How does erythromycin work as an antimicrobial?

A
  • Binds to 50s subunit
  • interferes with translocation of protein synthesis
  • as interferes with translocation = give rise to resistant mutations
23
Q

How does tetracycline & fusidic work as antimicrobials?

A

-Binds to 30s -blocking entry to tRNA complexes to their functional location on the ribosome

24
Q

How does clindamycin (lincosamide) work as an antimicrobial?

A

-Binds to 50s subunit = premature dissociation of peptidyl tRNA from the ribosomes.

25
Q

How does aminiglycosides (e.g. gentamicin & topical neomycin) work as an antimicrobial?

A

-Binds to 30s = misreading of mRNA = production of defective proteins

26
Q

What is fusidic acid used for?

A

treat angular chelitis where staphylococcal infection is identified.

27
Q

How does metronidiazole work as an antibacterial?

A

Interferes with bacterial nucleic acid synthesis:

  • interferes directly with the bacterial DNA - inhibits proteins synthesis & causes degradation of formed DNA = bacteriocidal
  • Only occurs in anaerobic bacterial
28
Q

Why is metronidazole known as a pro-drug?

A

Has to be metabolised to an active form (hydroxymetabolite) before it can have its effect.

29
Q

How does sulphonamides & trimethoprim work as antimicrobials?

A
  • Have antimetabolic action (inhibits cell metabolism)
  • Interferes with folate mechanism
  • Folate being essential for production of adenine & thymine (amino acids in DNA)