Antibiotics and Anti-fungals Flashcards

1
Q

Describe the distinctive features of: Gram positive bacteria, Gram negative bacteria and Mycolic bacteria

A

Gram +ve bacteria: Thick peptidoglycan cell wall
Gram -ve bacteria: Outer membrane contains lipopolysaccharide (LPS)
Mycolic bacteria: Outer mycolic acid layer

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2
Q

State the steps involved in the production of THF from PABA. What is THF important for ?

A

PABA –> DHOp (dihydropterase synthase)
DHOp –> DHF
DHF –> THF (DHF reductase)
THF important in nucleic acid synthesis

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3
Q

What is DNA gyrase?

A

A topoisomerase

Releases tension in DNA + is important in unwinding DNA to allow protein binding required for DNA replication

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4
Q

What does RNA polymerase do?

A

Produces RNA from a DNA template

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5
Q

What is the function of ribosomes? What is the key difference between ribosomes in eukaryotes and prokaryotes?

A

Produce protein from RNA templates
Eukaryote = 40S + 60S
Prokaryote = 30S + 50S

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6
Q

State 2 classes of drugs that interfere with nucleic acid synthesis and name the enzymes that they inhibit.

A

Sulphonamides: inhibits DHOp synthase
Trimethoprim: inhibits DHF reductase

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7
Q

Sulphonamides and Trimethoprim are sometimes used together. What is this preparation called?

A

Co-trimoxazole

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8
Q

Name a group of drugs that interfere with DNA replication and state its targets.

A

Fluoroquinolones inhibit bacterial DNA gyrase + topoisomerase IV

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9
Q

Name a group of drugs that interfere with RNA synthesis and state its main target.

A

Rifamycins inhibits bacterial RNA polymerase

Mainly used in tuberculosis

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10
Q

List 4 groups of drugs that inhibit ribosomes.

A

Macrolides e.g. Erythromycin
Aminoglycosides e.g. Gentamicin
Chloramphenicol
Tetracyclines

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11
Q

Describe how peptidoglycan is synthesized, transported to the cell wall and incorporated into the cell wall.

A

A pentapeptide is created on N-acetyl muramic acid (NAM)
N-acetyl glucosamine (NAG) associates with NAM forming peptidoglycan
PtG is transported across the membrane by bactoprenol
PtG is incorporated into the cell wall by transpeptidase enzyme, which cross-links PtG pentapeptides

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12
Q

Which groups of drugs interfere with peptidoglycan synthesis and how do they do this?

A

Glycopeptides (e.g. vancomycin): bind to pentapeptides + inhibit PtG synthesis
= a last resort for Gram+ve bacteria that are resistant to other antibiotics

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13
Q

Name a drug that interferes with peptidoglycan transport and state its target.

A

Bacitracin: inhibits bactoprenol regeneration, hence preventing PtG transport

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14
Q

Name a class of drugs that inhibit peptidoglycan incorporation and explain how they do this.

A

Beta lactams: bind covalently to transpeptidase, inhibiting PtG incorporation into the cell wall

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15
Q

What are the three subsets of beta lactams?

A

Carbapenems
Cephalosporins
Penicillins

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16
Q

Name two drugs that interfere with cell membrane stability and explain how they do this.

A

Lipopeptides: disrupt Gram +ve cell membranes
Polymyxins: bind to LPS + disrupt Gram -ve cell membranes

17
Q

List five mechanisms of antibiotic resistance and give a brief description of each.

A

Additional target: bacteria produce another target that is unaffected by the drug
Hyperproduction: increase production of the target so the antibiotics are less effective (though energy inefficient)
Altered target: alteration in drug target so drug is no longer effective (though enzyme is still effective)
Alteration in drug permeation: reduction of aquaporins or increase of efflux systems
Destruction enzymes: beta-lactamases hydrolyse C-N bond of b-lactam ring rendering b-lactams inactive

18
Q

What are penicillins G and V normally used to treat?

A

Gram-positive bacteria

19
Q

Name two drugs that are relatively beta lactamase resistant.

A

Flucloxacillin

Temocillin

20
Q

Name a broad-spectrum antibiotic that must be administered with another drug to become resistant to beta lactamases. What is this other drug?

A

Amoxicillin (no resistance on its own)

Clavulanic acid

21
Q

What are the four types of fungal infection, characterised based on the tissues/organs affected?

A

Superficial: outermost layers of skin
Dermatophyte: skin, hair or nails
Subcutaneous: innermost skin layers
Systemic: primarily respiratory tract

22
Q

What are the two main groups of anti-fungals? Give an example ofeach.

A

Azoles (fluconazole)

Polyenes (amphotericin)

23
Q

Describe the mechanism of action of azoles.

A

Inhibit CYP51p (enzyme of the CYP450 system), which is involved in ergosterol production

24
Q

Describe the mechanism of action of polyenes.

A

Interact with membrane sterols + form channels (punching holes in the membrane)

25
Q

Give an example of Gram positive bacteria, Gram negative bacteria and Mycolic bacteria

A

Positive: Staphylococcus aureus
Negative: Escherichia Coli
Mycolic bactéria: Mycobacterium Tuberculosis

26
Q

Give an example of when an azole and polyene would be used?

A

Azole: Candidiasis + Systemic infections
Polyene: Systemic infection