Antimicrobials - Antibiotics, antivirals, antifungals

Question 1

What are antibiotics?

Answer 1

Naturally produced antimicrobial agents

Question 2

What percentage of antibiotics are clinically useful?

Answer 2

Less than 1%

but these can be synthetically altered to increase efficacy

Question 3

What kind of drugs do Beta-lactam antibiotics comprise?

Answer 3

Penicillins
Cephalosporins
Cephamycins

Question 4

Penicillins and Cephalosporins comprise what percentage of antibiotic production?

Answer 4

Over 50%

Question 5

What fungus produces penicillin

Answer 5

Penicillin chrysogenum

Question 6

What is the beta-lactam method of action?

Answer 6

Potent inhibitors of cell wall synthesis
The transpeptidation (cross-linking) action is essential to cell wall synthesis
Transpeptidases can also bind to the beta-lactam ring (penicillin-binding proteins/PBPs)
The cell wall is still formed but with no cross links
It therefore becomes weak
Osmosis differences result in cell lysis

Question 7

Describe Cephalosporins structure

Answer 7

6 membered dihydrothiazine ring (penicillin has 5)

Semi-synthetic

Question 8

Cephalosporin method of action?

Answer 8

Same as penicillin

Question 9

Advantage of cephalosporins over penicillins?

Answer 9

More resistant to beta-lactamase enzymes

Question 10

Example of a Cephalosporin antibiotic?

Answer 10

Ceftriaxone used to treat Neisseria infections

Question 11

Describe the structure of aminoglycosides

Answer 11

Contain amino sugars bound via glycosidic bonding to each other

Question 12

Give 4 examples of aminoglycosides

Answer 12

Streptomycin, kanamycin, neomycin, gentamicin

Question 13

How do aminoglycosides work?

Answer 13

Inhibit protein synthesis at the 30S subunit of the ribosome

Question 14

Aminoglycosides are active against what type of bacteria?

Answer 14

Gram negatives

Question 15

What is the frequency of use of aminoglycosides like now?

Answer 15

declined and superseded by semi-synthetic penicillins e.g. ampicillin, oxacillin, methacillin

Question 16

First broad spectrum antibiotic class?

Answer 16

Tetracyclines

Question 17

Basic structure of tetracyclines?

Answer 17

naphthecene ring system

Question 18

How do tetracyclines work?

Answer 18

Interferes with 30S ribosome subunit function

Question 19

Wide use of tetracyclines in what area of medicine?

Answer 19

Veterinary

Question 20

What are growth factors?

Answer 20

Growth factors are specific substances required by microbes because they cannot synthesise them

Question 21

What are growth factor analogues?

Answer 21

Blocker of the utilisation of growth factors
synthetic compounds
structurally similar to growth factor but cannot duplicate their function within the cell

Question 22

Give an example of a sulfa drug

Answer 22

Sulfanilamide

Question 23

What is sulfanilamide

Answer 23

a growth factor analogue that is an analogue of p-aminobenzoic acid (PABA); a component of folic acid

Question 24

What process does sulfanilamide block?

Answer 24

The production of folic acid

Question 25

Where do bacteria get their folic acid from? What about eukaryotes?

Answer 25

Bacteria produce their own | Eukaryotes get it from their diet

Question 26

Name a growth factor analogue that is effective only against mycobacterium

Answer 26

Isoniazid | interferes with synthesis of mycolic acid

Question 27

How have nucleic acid base analogues been formed?

Answer 27

With the addition of bromine or flourine to an existing growth factor analogue

Question 28

What are quinolones? What do they do?

Answer 28

antibacterial compounds that interfere with DNA gyrase

Question 29

Give an example of a quinolone

Answer 29

ciprofloxacin

Question 30

What do antiviral drugs target?

Answer 30

Host structures, so generally are quite toxic

Question 31

Name the group of most successful and commonly used antivirals

Answer 31

nucleoside analogues

Question 32

Give an example of a nucleoside analogue antiviral drug

Answer 32

AZT

Question 33

How do nucleoside analogue antiviral drugs work?

Answer 33

Block reverse transcriptase and hence production of viral DNA

Question 34

Another name for nucleoside analogues?

Answer 34

Nucleoside reverse transcriptase inhibitors

Question 35

How do nonnucleoside transcriptaste inhibitors (NNRTIs) work?

Answer 35

Bind directly to reverse transcriptase and inhibit reverse transcription

Question 36

Name 3 classes of antiviral drug (excluding nucleoside analogues)

Answer 36

- Protease inhibitors - Fusion inhibitors - Interferons

Question 37

Name 2 categories of drug that limit influenza infection successfully

Answer 37

Adamantanes | Neuraminidase inhibitors

Question 38

How do protease inhibitor antivirals work?

Answer 38

inhibit the processing of large viral proteins into individual components

Question 39

How do fusion inhibitors work?

Answer 39

prevent viruses from successfully fusing with the host cell

Question 40

What are interferons and how do they work?

Answer 40

They are small proteins that prevent viral multiplication by stimulating antiviral proteins in uninfected cells

Question 41

Why do fungi pose special problems for chemotherapy?

Answer 41

Because they are eukaryotic | as a result, many antifungals are topical

Question 42

Name 7 things antifungal drugs can possibly target

Answer 42

- Membrane function - cell wall synthesis - ergosterol synthesis - nucleic acid synthesis - microtuble formation - folate synthesis - chitin synthesis

Question 43

How do antifungal drugs target membrane function?

Answer 43

Polyenes can bind to ergosterol and disrupt membrane integrity

Question 44

How do antifungal drugs target cell wall synthesis?

Answer 44

Polyoxins inhibit chitin synthesis Echinocandins inhibit glucan synthesis Echinocandins do this by inhibiting 1,3-beta-delta glucan synthase

Question 45

What antifungal drugs target ergosterol synthesis?

Answer 45

Azoles and allylamines inhibit it

Question 46

How do antifungal drugs target nucleic acid synthesis?

Answer 46

5-flourocytosine is a nucelotide analogue that inhibits nucleic acid synthesis

Question 47

How do antifungal drugs target microtuble formation?

Answer 47

Griseofulvin disrupts microtuble aggregation during mitosis

Question 48

Name a treatment for a Candida (fungal) infection

Answer 48

Echinocandins

Question 49

Name the most successful example of computer-aided drug design for antimicrobials

Answer 49

Saquinavir | Binds to active site of HIV protease

Question 50

What led to the discovery of platensimycin?

Answer 50

New methods of screening natural compounds | computer aided drug design etc.