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Infection and Immunology > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Antimicrobial drugs

A

Compounds that kill or control the growth of microorganisms IN the host

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2
Q

Antibiotics

  • define
  • 2 types
A

Compounds produced by 1 microorganism to kill or inhibit the growth of another microbe

Synthetic
Natural

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3
Q

Bacteriostatic drugs
Bactericidal
Bacteriolytic

A

Prevent the growth of a microorganism
Compounds that kill the microorganism
Compounds that lyse the microorganism

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4
Q

Major classes of antibiotics

A 
Fungal:
Beta-lactams 
Penicillins
Bacterial:
Glycopeptides
Aminoglycosides
Tetracylines
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5
Q

A good anti-microbial

= selectivity

A

Should kill or inhibit pathogen but not harm host

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6
Q

Ideal drug target

A

A structure bacteria possess but humans don’t
e.g. peptidoglycan cell wall

Good not to affect normal host microflora

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7
Q

Spectrum of drug activity

  • 2 types
  • examples
A

Broad spectrum
= active against Gram- positive and Gram-negatives
e.g. tetracycline

Narrow spectrum
= only kills certain group of bacteria
e.g. vancomycin used to treat penicillin-resistant Gram-positives

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8
Q

Antibiotic targets

A 
RNA elongation 
DNA-directed RNA polymerase
Protein synthesis (50S + 30S inhibitors, tRNA)
Lipid biosynthesis 
Cytoplasmic membrane structure 
Folic acid metabolism 
Cell wall synthesis 
DNA gyrase
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9
Q

Sulfanilamide

- strutcure

A

Structural analogue to para-aminobenzoic acid (PABA)

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10
Q

PABA

A

Precursor for folic acid biosynthesis

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11
Q

Folic acid biosynthesis

A

Needed for nucleotide biosynthesis

Bacteria have to synthesise own folic acid

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12
Q

Sulfanilamide

- role

A

Competitively inhibit folic acid synthesis

  • Humans unaffected as folic acid is a dietary supplement = Vit B9
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13
Q

Clinical resistance to sulpha drugs occurs

- then what happens?

A

2 drug combination:
Trimethoprim + sulfamethoxazole

Inhibits 2 sequential steps in folic acid biosynthesis
-> resistance less likely to arise

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14
Q

Quinolones

- role

A

Inhibitors of bacterial DNA gyrase/topoisomerase

  • responsible for supercoiling DNA
  • required for packaging DNA in bacterial cells + during DNA replication + transcription
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15
Q

Quinolones

- spectrum

A

Broad-spectrum

- all bacteria require DNA gyrase

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16
Q

Quinolones

e.g. Ciprofloxacin

A

> Used to treat UTIs
Treatment of respiratory disease in farm animals
Drug of choice against Anthrax

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17
Q

Beta-lactams

- role

A

Inhibitors of cell wall biosynthesis

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18
Q

Beta-lactam antibiotics contain…

Produced by…

A

> Penicillins
Cephalosporins
Carbapenems

All contain beta-lactam ring
- but differ in chemical nature of 2nd ring + side chains

Fungi

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19
Q

Penicillin

  • discovery
  • production
A

in 1928 by Fleming

Florey + Chain purified + conducted animal experiments
Pfizer developed use of large fermentation vats for commercial production

20
Q

Beta-lactams

- mode of action

A

Irreversible inactivation of transpeptidases

- PBPs = penicillin binding proteins

21
Q

PBPs

A

Catalyse transpeptidation + transglycosylation
= link between peptide side chains of peptidoglycan

Involves cleaving off the terminal D-Ala of the D-Ala-D-Ala end

22
Q

Beta-lactams

- inactivating PBPs

A

Beta-lactam mimics D-Ala-D-Ala peptide bond

AB binds + irreversibly blocks active site of PBP

No cleavage of cell wall can occur

  • > no growth
  • > cells lyse
23
Q

Beta-lactams

- only affect what cells?

A

Actively growing cells

24
Q

Cell walls

A

Nearly all bacteria possess a PG cell wall
- In Gram-negatives it’s surrounded by outer membrane
= intrinsically resistant

25
Q

Penicillins

- activity spectrum

A

Penicillin G can’t penetrate outer membrane of Gram-negative

Modification of N-acyl side group can change drug’s properties
- semi-synthetic drug

26
Q

Penicillins

- Modifications of N-acyl side group can cause…

A

Broaden spectrum to include Gram-negatives

Increase acid stability

Impart beta-lactamase resistance

27
Q

Antibiotic producers

A

Streptomyces

  • filamentous soil bacteria
  • produce ‘geosmin’ = damp forest smell

Produce 90% of the 3000 ABs produced by Actinobacteria

28
Q

Glycopeptides

- role

A

Inhibitors of cell wall biosynthesis

  • > bind to D-Ala-D-Ala
  • > blocks transpeptidation + transglycosylation
29
Q

Glycopeptides

- structure

A

Large, complex moleucles

Glycosylated, cyclic peptides synthesised by large multi-protein complexes

Non-ribosomally synthesised peptides

30
Q

Glycopeptide

- most important member

A

Vancomycin

31
Q

Glycopeptides

  • target
  • when is this useful?
A

Same as beta-lactams but different mechanism
= cell wall

Treatment of beta-lactam resistant infections

32
Q

Glycopeptides

- spectrum

A

Narrow spectrum

- only active against some Gram-positive bacteria

33
Q

Glycopeptides

- issues

A

Toxic to humans

+ strong side-effects

34
Q

Aminoglycosides

- role

A

Inhibitors of protein synthesis

-> targets 30S subunit of bacterial ribosomes by binding to 16s rRNA

35
Q

Aminoglycosides

- mechanism of action

A

Interferes with peptide elongation + translational proof-reading
-> truncated + aberrant proteins in cell
= non-functional

36
Q

Aminoglycosides

- type of AB

A

Bactericidal

37
Q

Aminoglycosides

- e.g.

A

Kanamycin

38
Q

Aminoglycosides

- spectrum

A

Broad spectrum

- mostly used if other drugs fail

39
Q

Tetracyclines

- role

A

Inhibit protein synthesis

40
Q

Tetracyclines

- mode of action

A

Interferes with 30S subunit and binds to 16S rRNA

-> inhibits binding of aminoacyl-tRNAs to A-site

41
Q

Tetracylines

  • type of AB
  • characterised by
A

Bacteriostatic

Naphthacene ring system
tetra + cyclins = 4 rings

42
Q

Tetracyclines

- natural + semi-synthetic analogues made

A

By modifying side groups of naphthacene ring

43
Q

Tetracyclines

- spectrum

A

V broad

- inhibits almost all Gram-Positive and negative bacteria

44
Q

New ABs in the media

- New AB discovered

A

New method for culturing bacteria from soil (new approach)

  • > discovered Teixobactin (new drug)
  • > targets Lipid II (old target)
45
Q 
New ABs in the media 
- New class of AB
A

Culture-independent method using DNA extracted from soil (new approach)

  • > Malacidins (new drugs)
  • > Targets Lipid II (old target)

Infection and Immunology (13 decks)

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