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RW Pathology > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Mechanism of action of Antibiotics

A 
Inhibit cell wall synthesis
------- β lactams(Penicillin, Cephlosporin, Carbapenems)
------- Glycopeptides (Vancoymycin, Teicoplanin)
Inhibit protein synthesis
------- Aminoglycosides (Gentamicin)
------- Tetracycline (Doxycycline)
------- Macrolide (Erythromycin)
------- Chloramphenicol
------- Oxazolidinones (Linezolid)
Inhibit DNA synthesis
------- Fluoquinolone (Ciprofloxacin)
------- Nitroimidazoles (Metronidazole)
Inhibit RNA synthesis
------- Rifamycin (Rifampacin)
Cell membrane toxin
------- Polymyxin (Colistin)
------- Cyclic lipopeptide (Daptomycin)
Inhibit folate metabolism
------- Sulfonamide (Sulphamethoxazole)
------- Diaminopyramidines (Trimethoprim)
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2
Q

Differences in cell structure in Gram +ve and Gram -ve

A

Gram +ve have thick peptidoglycan cell wall

Gram -ve have thin peptidoglycan cell wall + outer membrane

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3
Q

Inhibit cell wall synthesis

A
  • —– β lactams(Penicillin, Cephlosporin, Carbapenems)

- —– Glycopeptides (Vancoymycin, Teicoplanin)

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4
Q

Examples of βlactams

A 
Penicillin
---- Benzylpenicillin
Cephalosporin
---- 3rd gen: Ceftriaxone, Cefotaxime, Ceftrazidime
---- 2nd gen: Cefuroxime
---- 1st gen: Cephalexin
Carbapenams
---- Meropenam
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5
Q

MOA of β lactams

A

Bind to penicillin-binding proteins –> ↓cell wall cross links –> weaker membrane –> lysed

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6
Q

Risk of cross-reactivity between βlactams

A

0.1

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7
Q

Co-amoxiclav

A

Amoxicillin + Clavulanic acid

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8
Q

Tazocin =

A

Piperacillin + Tazobactam

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9
Q

With ↑generation of cephalosporin

A

↑Gram -ve cover, ↓Gram +ve cover

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10
Q

Why is Cef (cephalosporin) often given with Metronidazole

A

Met provides anerobe cover

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11
Q

ESBL stands for

A

Extended spectrum β-lactams

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12
Q

ESBL Tx

A

Carbapenam-sensitive

Resistant to Penicillin and Cephalosporins)

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13
Q

Carbapenemase

A

Resistant to Pencillin, Cephalosporin and Carbapenem

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14
Q

Inhibit protein synthesis

A

Inhibit protein synthesis (cATOM)

  • —— Aminoglycosides (Gentamicin)
  • —— Tetracycline (Doxycycline)
  • —— Macrolide (Erythromycin)
  • —— Chloramphenicol
  • —— Oxazolidinones (Linezolid)
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15
Q

Example of Glycopeptides

A

Vancomycin, Teicoplanin

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16
Q

MOA of Glycopeptides

A

Bind to enzymatic target (peptidoglycan precursors) –> weakened cell wall –> lyse
Similar MOA in β lactams bt bind to substrate (precursors)

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17
Q

Nephrotoxic ABx

A

Gentamicin, Amikacin (aminoglycosides)

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18
Q

Example of Aminoglycoside

A

Gentamicin, Amikacin, Tobramycin

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19
Q

MOA of Aminoglycosides

A

Aminoglycoside binds to 30S ribosomal subunit to prevent causing misreading of dcodons along the mRNA–> inhibits protein synthesis

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20
Q

Example of Tetracycline

A

Doxycycline

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21
Q

MOA of Tetracycline

A

Binds to 30S ribosomal subunit to prevent aminoacyl-tRNA binding –> inhibits protein synthesis

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22
Q

Example of Macrolide

A

Azithromycin, Clarithromycin

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23
Q

MOA of Macrolide

A

Binds to 50S ribsomal subunit –> prevents binding of peptidyl-tRNA

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24
Q

MOA of Chloramphenicol

A

Binds to 50S ribsomal subunit –> Prevents formation of peptide bonds

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25
Q

Example of Oxazolidinone

A

Linezolid

26
Q

Inhibit DNA synthesis

A

Inhibit DNA synthesis

  • —— Fluoquinolone (Ciprofloxacin)
  • —— Nitroimidazoles (Metronidazole)
27
Q

MOA of Oxazolidinone

A

Binds to 23S component of 50S subunit to prevent formation of functional 70S initial complex

28
Q

Example of Quinolone

A

Ciprofloxacin

29
Q

MOA of Fluroquinolone

A

Bind to DNA gyrase –> inhibit DNA synthesis

30
Q

Example of Nitroimidazole

A

Metronidazole, Nitrofurantoin (related)

31
Q

MOA of Nitroimidazole

A

Under anerobic conditions, active intermediated is produced which causes DNA strand breakage

32
Q

Inhibit RNA synthesis

A

Inhibit RNA synthesis

——- Rifamycin (Rifampacin)

33
Q

Example of Rifamycin

A

Rifampicin

34
Q

MOA of Rifampicin

A

Binds to RNA polymerase –> inhibits initiation –> Inhibits RNA synthesis
S/E organse secretions, Liver enzyme inducer

35
Q

Cell membrane toxin

A

Cell membrane toxin

  • —— Polymyxin (Colistin)
  • —— Cyclic lipopeptide (Daptomycin)
36
Q

Examples of cell membrane toxins + MOA

A

Daptomycin - inserts into cell membranes –> leak ions

Colistin –> unknown

37
Q

Inhibit folate metabolism

A

Inhibit folate metabolism

  • —— Sulfonamide (Sulphamethoxazole)
  • —— Diaminopyramidines (Trimethoprim)
38
Q

Example of Sulfonamide + MOA

A

Sulphmethoxazole –> interferes with folate metabolism

39
Q

Example of Diaminopyrimidine + MOA

A

Trimethoprim –> interferes with folate metabolism

40
Q

Co-trimoxazole =

A

Sulphamethoxazole + Trimethoprim

41
Q

Mechanisms of ABx resistance

A

BEAT drug action

  • Bypass ABx sensitive step in pathway (Trimethoprim)
  • Enzymatic drug inactivation (β lactamase)
  • ↓Accumulation of drug (Tetracycline resistance) - ↓uptake or efflux
  • change drug Target (MRSA, Quinolone resistance)
42
Q

β-lactamases - types, act against

A

Breaks down β lactams

  • β-lactamase (against Penicillin)
  • ESBL (against cephalosporins)
  • AmpC (against cephalosporins, not inhibited by Clavulanic acid)
  • Carbapenemase (against all β lactams)
43
Q

MRSA - resistance mechanism

A

Altered target (mecA gene encodes novel PBP called PBP-2a)

44
Q

Abx for ESBL

A

β-lactam + Aminglyocoside (Gentamicin, Amikasin)

45
Q

ABx for MRSA

A

Vancomycin (or Linezolid)

46
Q

Abx for C diff

A

Metronidazole (or Vancomycin)

47
Q

Abx for Chlamydia

A

Doxycycline

48
Q

ABx for bacterial conjunctivitis

A

Chloramphenicol

49
Q

ABx for VRE

A

Linezolid

Daptomycin

50
Q

Cover for anerobes

A

Metronidazole

51
Q

ABx fo PCP

A

Co-trimoxazole = Trimethoprim + Sulphamethoxazole

52
Q

ABx for UTI

A

Trimethoprim or Nitrofurantoin

53
Q

ABx for pseudomonas

A

Gentamicin, or Tazocin

54
Q

Main ABx for S aureus

A

Flucluoxacillin

55
Q

Main ABx for meningitis

A

Ceftriaxone +/- Amoxicillin (listeria cover)

56
Q

ABx for pharyngitis

A

Benzylpenicillin

57
Q

ABx for CAP (mild)

A

Amoxicillin

58
Q

ABx for CAP (severe)

A

Co-amoxiclav + Clarithromycin

59
Q

ABx for HAP

A

Amoxicillin + Gentamicin OR Tazocin

60
Q

Abx for E. coli

A

Gentamicin

RW Pathology (9 decks)

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