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LCRS Pharmacology and Therapeutics > Antibiotics and antifungals > Flashcards

Antibiotics and antifungals Flashcards

1
Q

Give a basic overview of structure of gram positive bacteria and name a common example?

A

Prominent peptidoglycan cell wall

e.g. staph aureus

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2
Q

Give a basic overview of the structure of gram negative bacteria and name a common example?

A

Outer membrane that contains lipopolysaccharide

e.g. E. coli

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3
Q

What are mycolic bacteria like?

A

They have an outer mycolic acid layer e.g. mycobacterium tuberculosis

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4
Q

In nucleic acid synthesis, what is dihydropterate (DHOp) synthesised by?

A

Paraaminobenzoate (PABA) by the enzyme dihydrojpterate synthase

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5
Q

What happens to DHOp after formation?

A

It is then converted to dihydrofolate (DHF)

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6
Q

What is produced from DHF?

A

Tetrahydrofolate (THF) by DHF reductase

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7
Q

What is THF important in?

A

DNA synthesis

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8
Q

What is DNA gyrase the same as?

A

Topoisomerase

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9
Q

What is DNA gyrase important for?

A

Unwinding DNA to allow protein binding required for DNA replication- releases tension in the DNA

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10
Q

What does RNA polymerase do?

A

Produces RNA from a DNA template

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11
Q

What do ribosomes do?

A

Produce proteins from RNA templates

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12
Q

What is the difference between eukaryotic and prokaryotic ribosomes

A 
Eukaryotes= 60s +40s
Prokaryotes= 50s + 30s
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13
Q

Why are ribosomes good drug targets?

A

They are different in prokaryotes and eukaryotes

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14
Q

What do sulphonamides do?

A

They inhibit dihydropterate synthase thus inhibit prokaryotic nucleic acid synthesis

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15
Q

Why are sulphonamides not really used anymore?

A

Widespread antibiotic resistance

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16
Q

What does trimethoprim do?

A

Inhibits DHF reductase

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17
Q

What is co-trimoxazole?

A

Combined preparation of sulphonamides and trimethoprim

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18
Q

What do fluoroquinolones do?

A

They inhibits bacterial DNA gyrate and topoisomerase IV

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19
Q

What is the difference between fluoroquinolones and quinolones?

A

Same mechanism but less resistance

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20
Q

What do rifamycins do?

A

Inhibit bacterial RNA polymerase- prevent RNA synthesis

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21
Q

What inhibit ribosomes?

A

Aminoglycosides e.g. Gentamicin
Chloramphenicol
Macrolide’s e.g. erythromycin
Tetracyclines

22
Q

In bacterial cell wall synthesis, how is peptidoglycan formed?

A

A pentapeptide is created on N-acetyl muramic acid (NAM). N-acetyl glucosamine (NAG) associated with NAM forms peptidoglycan

23
Q

Where is the peptidoglycan formed?

A

Inside the bacterial cell

24
Q

What happens to peptidoglycan once formed?

A

It is transported across cell membrane and periplasm to cel wall using bactoprenol

25
When peptidoglycan is at the cell wall, what happens?
The proteoglycan is incorporated into the cell wall when transpeptidase enzymes cross links the peptidoglycan pentapeptides
26
What do glycopeptides e.g. vancomycin do?
They bind to the pentapeptide thus preventing PtG synthesis
27
When are glycopeptides used?
As a last resort mainly for Gram positive bacteria that are resistant to other antibiotics
28
What does bacitracin do?
Inhibits bactopreol regeneration thus prevents PtG transportation
29
What do beta-lactams do?
They bind covalently to transpeptidase which inhibits PtG incorporation into the cell wall
30
Give examples of beta lactams?
Carbapenems Cephalosporins Penicillins
31
What do lipopeptides e.g. daptomycin do?
Disrupt Gram Positive cell walls
32
What do polymyxins do?
They bind to lipopolysaccharide and disrupts gram negative cell membranes
33
What are the causes of antibiotic resistance?
Unnecessary prescription Livestock farming Lack of regulation Lack of development
34
How does the additional target mechanism work?
Bacteria produce another target that is similar to actual target but this one fools the drug as it is unaffected by the drug so the actual target can function properly
35
Give an example of the additional target mechanism?
E coli produce different DHF reductase enzymes making them resistant to trimethoporin
36
How does the hyperproduction mechanism work?
Bacteria significantly increase production of DHF reductase so increases DNA synthesis
37
Why is hyper production not a common mechanism of antibiotic resistance?
Hyper production requires a lot of energy
38
How does alterations in target enzymes lead to antibiotic resistance?
There is an alteration to the enzyme that is targeted by drug so enzyme will still be effective but drug will be ineffective Widely used method
39
Give an example of the alteration in target enzyme mechanism?
S.aureus- Mutation in ParC region of topoisomerase IV confers resistance to quinolone
40
What are aquaporins required for?
To allow drugs access to cells
41
How does the alterations in drug permeation mechanism work?
The bacteria decreases number of aquaporins- reduces access to the cell Another mechanism is increase efflux systems- drug gets kicked out quickly Common method
42
How does the production of destruction enzymes work?
Beta lactamases hydrolyse the C-N bond of beta lactic ring
43
Give examples of production of destruction enzymes mechanism?
Pencillins G and V commonly used for gram positive bacteria Flucloxacillin and temocillin are relatively beta lactamase resistant Amoxicillin is broad spectrum antibiotic which isn't resistant to beta lactamases
44
Give all the mechanisms of antibiotic resistance?
``` Additional target Hyperproduction Alteration in target enzymes Alteration in drug permeation Production of destruction enzymes ```
45
What are fungal infections classified based on?
``` In terms of tissues/organs affected: Superficial-outermost layers of skin Dermatophyte- Skin, hair or nails Subcutaneous- innermost skin layers Systemic- Primarily respiratory tract ```
46
What are the two most common categories of anti-fungals?
Azoles- Fluconazole | Polyenes- Amphotericin
47
What do azoles do?
Inhibit cytochrome p450 dependent enzyme involved in ergosterol synthesis
48
What is fluconazole used for?
Azole that is used in candiadis and systemic infections
49
What do polyenes do?
Interacts with membrane sterols forming membrane channels- punch holes in cell membrane which destroys cell viability
50
What is amphotericin used for?
Systemic infections

LCRS Pharmacology and Therapeutics (33 decks)

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