2.2 Antimicrobial agents Flashcards

1
Q

antibiotic mechanisms (4)

A

1 inhibit cell wall synthesis
2 inhibit protein synthesis
3 interferes with DNA synthesis and replication
4 disrupts cell membrane

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2
Q

what antibiotics inhibit cell wall synthesis

A

beta lactam and glycopeptide

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3
Q

beta lactam antibiotic examples

A

penicillins, cephalosporins and carbapenems
beta lactams contain a ring of carbons and modifiable residues
have been many generations of cephalosporins
carbapenems are last line antibiotics, main one is meropenem which is broad spectrum

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4
Q

describe beta lactam mode of action

A

penicillin blocks the active site through penicillin binding protein so the bacteria can’t form the cell wall properly and it breaks open (think of it as punching holes in cell wall)
Inhibiting transpeptidases from linking amino acid side chains.

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5
Q

what are beta lactamase inhibitors and why are they needed

A

bacteria produce beta lactamases to hydrolyse the beta lactam ring of antibiotic to make it ineffective. So beta lactamase inhibitors block their active site to prevent them destroying the antibiotic, such as clavulanic acid, to leave the antibiotic free to work. E.g. co-amoxiclav= amoxicillin and clavulanic acid

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6
Q

glycopeptide antibiotics examples

A

vancomycin and teicoplanin, have broad gram positive spectrum

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7
Q

describe glycopeptide mode of action and how resistance occurs

A

they bind directly to amino acid side chains, so cell wall cross-linking enzymes can’t attach, resistance occurs when bacteria modify side chain structures

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8
Q

give examples of antibiotics that inhibit protein synthesis, will they have an immediate effect?

A

macrolides, tetracyclines and aminoglycosides
they may not have an immediate effect with bacteria need to constantly turn protein over so blocking this will interfere with growth

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9
Q

example of macrolides

A

clarithromycin- used to treat community acquired pneumonia

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10
Q

example of tetracyclines

A

Doxycycline- oral and long lasting, used in COPD

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11
Q

example of aminoglycosides

A

gentamicin- narrow therapeutic window since can damage kidneys, used for sepsis

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12
Q

give examples of antibiotics that inhibit DNA synthesis and replication

A

sulphonamides, diaminopyrimidines and quinolones

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13
Q

what do antibiotics that inhibit DNA synthesis and replication exploit

A

the fact that bacteria have to synthesis folate and cannot absorb it, they interfere with folate synthesis at different stages, use more than one to be more powerful and reduce the chance of resistance (synergistic activity)

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14
Q

what is fluroquinolone and what is it used for

A

fluorine atom and quinolone, stops DNA unwinding before replication by binding to 2 nuclear enzymes. Causes shredded DNA, rapidly fatal to bacteria

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15
Q

fungi are (p or e)

A

eukaryotes (have a nucleus)

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16
Q

what is mycosis

A

a disease caused by fungal infection

17
Q

give 3 examples of antifungal drug types

A

azoles, polyenes and echinocandins

18
Q

surgical patients are prone to infections of

A

candida- lots in the gut

19
Q

explain antifungal mode of actions

A

cell wall is ergosterol based rather than human cholesterol, so they interfere with the ergosterol pathway or bind directly to it

20
Q

what antibiotics act on the 30s ribosomal subunit

A

aminoglycosides and tetracyclines

21
Q

what antibiotics act on the 50s ribosomal subunit

A

macrolides and chloramphenicol

22
Q

give an example of triazoles, polyenes and echinocandins

A

fluconazole (broad), amphotericin B (I.V for systemic mycoses) and caspofungin (less toxic than Amph.B)

23
Q

give an example of penicilins, cephalosporins and carbapenems

A

flucloxacillin, cefalexin and ertapenem