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Fundamentals of Pharmacology > Antibacterial Drugs - Chemotherapy > Flashcards

Antibacterial Drugs - Chemotherapy Flashcards

1
Q

Why can doctors not tell the specific bacterial infection from symptoms and signs?

A

Many bacteria can cause the same symptoms.

The symptoms depend on the site, extent of infection and local reaction

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2
Q

What are the categories of bacteria?

A

Gram positive

Gram negative

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3
Q

What is antibacterial chemotherapy?

A

Chemicals or substances produced by microorganisms to kill or prevent the growth of other microorganisms

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4
Q

What are the drugs that prevent the growth of a bacterial colony?

A

Static drugs (only prevent proliferation of bacteria)

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5
Q

What are the drugs that kill the bacteria in a colony reducing their numbers?

A

Cidal drugs (will remove bacteria)

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6
Q

What are broad spectrum antibacterial drugs?

A

Affect a wide range of bacterial species and hence are very effective antibiotics

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7
Q

What are narrow spectrum antibacterial drugs?

A

Antibiotics which can effect a single bacterium and hence are more easily treated against harmful bacteria.

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8
Q

What is an important characteristic of most antibacterial drugs?

A

High selective toxicity

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9
Q

What is high selective toxicity?

A

The ability of a drug to effect its target efficiently without causing side effect or by effecting other body cells.

Exploitable differences between the organism and the host

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10
Q

what are the main differences between bacterial and mammalian cells?

A

Peptidoglycan cell wall

Plasma membrane without sterols

single circular chromosome

Protein synthesis

Energy metabolism (no mitochondria)

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11
Q

What is a class 1 reactions?

A

not good targets for chemotherapy as they are very similar to human reactions.

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12
Q

What are class 2 reactions?

A

Some mechanisms are specific to the bacteria.

Identical pathway but might have different sensitivity to the drug

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13
Q

What is an example of class II drug class?

A

Folate (vitamin B) essential in DNA replication

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14
Q

What are class 3 reactions?

A

Best drug target.

Products made up of different composition/ structure specific to the bacteria

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15
Q

Why are class 3 reactions the best chemotherapy targets?

A

Because these reactions are most different between human and bacterial cells and every cell must make its own specific macromolecules

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16
Q

What is folate metabolism?

A

Humans must produce folate to make DNA

17
Q

What are the differences in the folate metabolism between humans and bacteria?

A

Bacteria:
Produce their own folate
Cannot transport it into their bodies
Have the mechanisms to make their own folate

Humans:
Cannot produce own folate
Transport mechanisms to take up preformed folate

18
Q

What drug interferes with nucleic acid synthesis?

A

Sulphonamides by inhibiting production of folate

19
Q

Why do sulphonamides work as inhibitors of folate production?

A

Analogue of p-aminobenzoic acid (PABA) essential for folate synthesis.
competitive antagonist

Prevent PABA -> folate and therefore folate -> tetrahydrofolate -> DNA

20
Q

What drug is most effective in targeting bacterial folate production?

A

Trimethoprim

effects bacterial cells as there is differential sensitivity between folate to tetrahydrofolate in bacterial and mammalian cells.

21
Q

Why can you not treat infections characterised with pus with sulphonamides?

A

Since pus is broken down tissue and therefore high in purines and pyrimidines and hence means that even if the folate metabolism is prevented through antibiotics, the bacteria can still make DNA through absorbing the purines/pyrimidines instead.

22
Q

What is one of the main targets for bacteria and what drugs effect this?

A

Peptidoglycan synthesis: highly selective as human cells don’t have this structure.

Penicillin's
Beta-lactams
Cycloserin
Glycoproteins
Bacitracin
23
Q

What leads to resistance of penicillin?

A

Production of Beta-lactamase

24
Q

What bacteria can produce beta-lactamase and are therefore resistant to penicillin and what other wways is penicillin resistance occuring?

A

Staphylococci
Gonorrheae
Hemophilus

Reduction of membrane permeability

Modified penicillin binding sites

25
Q

How do drugs inhibit peptidoglycan synthesis of the cell wall?

A

Beta Lactams:

Interfere with peptidoglycan synthesis (peptide crosslinks) by affecting transpeptidase

26
Q

What drugs increase permeability of the cytoplasmic membrane?

A

Polymixin B - Effective against gram -tve

Gramicidin - effective against gram +tve

27
Q

What do tetracyclins do?

A

Inhibit protein synthesis by competing with the tRNA for the A site on the ribosome

Selective uptake into prokaryotes

28
Q

What do Streptomycins do?

A

Inhibit protein synthesis by leading to the misreading of the anticodon recognition site

29
Q

What do Puromycins do?

A

inhibit protein synthesis by the premature termination of the peptide chain

30
Q

What does Erthromycin do?

A

Inhibit protein synthesis via the inhibition of translocation of the polypeptide chains making them too short and therefore non-functional proteins.

31
Q

What drugs inhibit nucleic acid synthesis?

A

DNA/RNA Polymerase - Rifampicin

DNA gyrase - quinolones

Base pairing properties - Proflavin

32
Q

What drugs interfere with energy metabolism?

A

Metronidazole - cytotoxic products destroys the cell

Effective against anaerobic bacteria and protozoa

33
Q

What side effects are caused by metronidazole?

A

Nausea

Metallic taste

34
Q

What are the factors that affect the success of chemotherapy?

A

Drug resistance

35
Q

Why are resistant bacteria a problem?

A

Have a selective advantage over sensitive bacteria.
Therefore when other bacteria are killed off this provides the growth space and nutrients for the resistant bacteria to multiply more easily and therefore spread.

36
Q

What are the mechanisms of drug resistance?

A

Altered drug targets or metabolic pathways

Decreased access/increased export

Drug inactivation

37
Q

How can we avoid antibiotic resistance?

A

Prudent antibiotic use

Targeted antibiotic use

Optimal dosages and regimens

Preventing infections: vaccines, hygiene

Fundamentals of Pharmacology (19 decks)

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