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YR5 Microbiology > Antimicrobial agents 1 > Flashcards

Antimicrobial agents 1 Flashcards

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1
Q

What is the broad mechanism of action of beta lactams?

A

Inhibition of cell wall synthesis

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2
Q

What is the broad mechanism of action of glycopeptide antibiotics?

A

Inhibition of cell wall synthesis
Bind to peptide crosslink sticking out of pep glycol precursor, prevent bond formation

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3
Q

What 3 groups of antibiotics are classified as beta lactams?

A

Penicillins
Cephalosporins
Carbapenems

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4
Q

Name 2 glycopeptide antibiotics

A

Vancomycin
Teicoplanin

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5
Q

Describe the mechanism of action of beta lactams

A

Inactivates transpeptidase enzyme that forms X-links during cell wall synth.
Resulting cell wall is weak, so bacteria lyse because of osmotic pressure.

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6
Q

What bacteria is penicillin active against?

A

+ve

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7
Q

What bacteria is amoxicillin active against?

A

BS: +ve, enterococci + gm -ve

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8
Q

Is streptococci gram pos or neg?

A

+ve

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9
Q

Which beta lactam antibiotic is effective against pseudomonas?

A

Piperacillin-Tazobactam
(Tazocin)

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10
Q

How can beta lactam resistance be overcome?

A

Include a B-lactamase inhibitor
E.g. Amoxicllin + Clavulanic acid (co-amoxiclav)
Piperacillin + Tazobactam (Tazocin)

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11
Q

Is pseudomonas gram pos or gram neg?

A

-ve bacilli
(Pseudo”moan”as ‘moan’ = negative)

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12
Q

Is neisseria meningitis gram pos or gram neg?

A

-ve cocci
(Neisseria starts with N = negative)

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13
Q

Recall 3 antibiotics associated with C. difficile

A

Ceftriaxone (cephalosporin)
Clindamycin (lincomycin)
Ciprofloxacin (fluoroquinolone)

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14
Q

Which beta lactam antibiotics are stable to ESBL organisms?

A

Carbapenems

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15
Q

Recall 3 cautions of beta lactam antibiotic

A

Excreted renally: reduce dose if renal impairment
Short half life: multiple doses spaced equally required
Cross-allergenic (penicillins 10% X-reactivity with cephalosporins/ carbapenems)

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16
Q

What type of bacteria are glycopeptides effective against?

A

+ve only
Are large molecules so can’t penetrate -ve outer cell wall

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17
Q

What infection are glycopeptides particularly useful for?

A

MRSA

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18
Q

What is a caution of glycopeptide antibiotics?

A

Nephrotoxic
Monitor levels to prevent accumulation

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19
Q

Recall the broad mechanism of action of glycopeptide antibiotics

A

Prevent peptide X-links in cell wall

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20
Q

What type of bacteria are aminoglycoside antibiotics effective against?
Recall MOA of aminoglycosides

A

-ve
Bind to 30s ribosomal subunit, preventing elongation of polypeptide chain
No anaerobic activity

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21
Q

Recall 2 examples of aminoglycoside antibiotics

A

Gentamicin (effective in P. aeruginosa)
Amikacin

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22
Q

Recall 2 toxicities of aminoglycosides

A

Ototoxicity
Nephrotoxicity

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23
Q

What type of bacteria are macrolides effective against?

A

+ve
Bind to 50s subunit of ribosomes

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24
Q

What are macrolides particularly useful for? What else are they active against?

A

Mild staph or strep infections in penicillin allergic
Campylobacter sp + legionella pneumophila

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25
Q

Recall 3 macrolide antibiotics

A

Azithromycin
Clarithromycin
Erythromycin

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26
Q

What type of bacteria are tetracylines effective against?

A

BS
Intracellular pathogens e.g. Chalmydiae, Rickettsiae, Mycoplasma

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27
Q

Recall a class of antibiotic you should never give to children or pregnant women

A

Tetracyclines
as
TERATOGENIC, deposit in growing bones

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28
Q

Recall one side effect of tetracycline antibiotics

A

Light-sensitive rash
Avoid sun

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29
Q

Recall the broad mechanism of action of tetracyclines

A

Bind to 30s subunit of ribosomes

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30
Q

What type of bacteria is chloramphenicol effective against? What may chloramphenicol be used for?

A

V Broad Spectrum
Eye drops

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31
Q

Why is chloramphenicol rarely used?

A

Risk of aplastic anaemia + grey baby syndrome in neonates due to inability to metabolise drug

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32
Q

Recall the broad mechanism of action of chloramphenicol

A

Binds 50s subunit of ribosomes
Inhibits formation of peptide bonds during translation

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33
Q

Recall the broad mechanism of action of oxazolidinones

A

Binds 23s + 50s subunit of ribosomes to prevent 70s subunit formation

34
Q

Recall two types of bacteria that oxazolidinones are particularly active against

A

Highly active against gram +ve, inc:
MRSA + VRE

35
Q

Recall an example of oxazolidinones

A

Linezolid

36
Q

Recall one potential side effect of oxazolidinones

A

Thrombocytopaenia
(+ expensive)
(+ can cause serotonin syndrome)

37
Q

Recall the MOA of fluoroquinolones

A

Act on alpha subunit of DNA gyrase
Broad activity, esp. vs -ve inc. P aeruginosa
Levo + Moxi have activity against +ve and intracellular e.g. Chlamydia

38
Q

Recall 4 uses of fluoroquinolones

A

UTI
Pneumonia
Atypical pneumonia
Bacterial gastroenteritis

39
Q

Recall 3 examples of fluoroquinolone antibiotics

A

Ciprofloxacin
Levofloxacin
Moxifloxacin

40
Q

Give an example of a nitromidazole antibiotic

A

Metronidazole

41
Q

Recall types of organisms that metronidazole is effective against

A

Anaerobes
Protozoa e.g. Giardia

42
Q

When should metronidazole be taken?

A

Right after visiting the toilet as it sits in bladder

43
Q

Recall the broad mechanism of action of rifampicin

A

Inhibits RNA polymerase

44
Q

Recall the main use of rifampicin

A

TB

45
Q

Recall one side effect of rifampicin

A

Turns secretions orange

46
Q

Recall one condition of rifampicin prescription

A

Never prescribe alone as resistance develops very quickly

47
Q

Name 2 cell membrane toxins. How do their activity differ from other antibiotics?

A

Daptomycin. +ve. Limited by surfactant, not good in lungs.
Colistin. -ve. Nephrotoxic, reserved for MR bacteria
Work when bacteria are NOT active.

48
Q

What is daptomycin licensed for the treatment of?

A

MRSA
VRE

49
Q

Recall the 2 classes of antibiotic that inhibit folate metabolism

A

Sulphonamides
Diaminopyrimidines e.g. Trimethoprim

50
Q

What does Trimethoprim combined with sulfamethoxazole form? What is this used for?

A

Septrin (co-trimazole)
PCP
Elderly- doesn’t exacerbate C diff

51
Q

What is the main use of trimethoprim alone?

A

Uncomplicated UTI

52
Q

What are the 4 main mechanisms of resistance

A
  1. Inactivation- B latamases
  2. Altered target (abx no longer binds - important in MRSA where bacteria change PBP, + in protein-synthesis inhibitors where binding of ribosome subunit is prevented)
  3. Reduced accumulation
    (most important in gram -ve: either due to efflux or to reduced uptake)
  4. Bypass
    (important for folate inhibitors: bacteria can change the enzyme they use)
53
Q

Name 2 classes of abx that inhibit DNA synthesis

A

Fluoroquinolones
Nirtromidazoles

54
Q

Which bacteria typically forms “gram pos cocci in clusters”?

A

Staphylococcus

55
Q

Which bacteria typically forms “gram pos cocci in chains”?

A

Streptococcus
Strep sounds like ‘stripe’ = chain

56
Q

What gram stain status are enterococci?

A

+ve
(“Enter-o-coccus” = like letting someone in, +ve thing to do)

57
Q

Is haemophilus gram pos or neg?

A

-ve
Ha”emo”philus - emo = -ve

58
Q

Is listeria gram pos or neg?

A

+ve
Lister = good man = +ve

59
Q

How do gram positive and negative bacteria differ in their cell walls?

A

+ve: THICK peptidoglycan
-ve: THIN peptidoglycan, have outer membrane

60
Q

Against which cells are b-lactams ineffective against?

A

Those lacking pep wall: Chlamydia + Mycoplasma
Those not metabolically active/ dividing: biofilms/ abscesses/ prostheses

61
Q

What is transpeptidase also known as?

A

Penicillin binding protein

62
Q

Which penicillin is penicillinase stable? Against which bacteria does this allow use for compared to other penicillins?

A

Flucloxacillin
Use against S aureus

63
Q

Describe the components of Co-amoxiclav

A

Clauvanic acid is a b-lactamase inhibitor allows Amoxicillin to retain activity

64
Q

Give examples of each generation of cephalosporin. How do they differ?

A

Increasing activity against -ve bacilli
1: Cephalexin
2: Cefuroxime
3: Cefotaxime, Ceftriaxone, Ceftazidime

65
Q

What is ceftazidime most commonly used for?

A

Anti-pseudomonas

66
Q

Which enzymes confer resistance to Cephalosporins? What drug may be used instead?

A

ESBL
Rx: Carbapenem e.g. Meropenem

67
Q

Give 3 examples of Carbapenems

A

Meropenem
Imipenem
Ertapenem

68
Q

Which emerging enzymes would confer resistance to Meropenem?

A

Carbapenemase

69
Q

How do B lactase interact with the blood brain barrier?

A

Intact: DONT cross (non-inflamed meninges)
Meningitis: cross BBB as high dose used + inflamed meninges

70
Q

Why are B lactams more preferable to glycopeptides?

A

Glycopeptides are slowly bactericidal

71
Q

What can Vancomycin PO be used to treat?

A

Serious C. difficile

72
Q

2 examples of glycopeptides

A

Vancomycin
Teicoplanin

73
Q

Give 5 classes of protein synthesis inhibitor antibiotics

A

Aminoglycosides
Tetracyclines
Macrolides
Chloramphenicol
Oxazolidinones

74
Q

2 side effects of fluoroquinolones

A

Tendonitis
Lowers seizure threshold

75
Q

What is a related class of compounds to Nitroimidazoles?

A

Nitrofurans- Nitrofurantoin used in simple UTIs

76
Q

Why does DH need to be considered when prescribing Rifampicin?

A

Enzyme inducer
Increases rate of metabolism of drugs metabolised by liver

77
Q

How can Streptococcus pneumoniae resistance be overcome?

A

Mutation: Becomes step-wise resistant with altered PBP
Overcome with high dose if low level resistance

78
Q

Why has there been tx failure reported with B lactamase inhibitors?

A

In ESBL +ve bacteria
Traditional inhibitors don’t work against all enzymes

79
Q

What is the mechanism of resistance to macrolides?

A

Altered target: ribosomal methylation encoded by ERM gene
Ribosome which macrolide binds to is altered, no longer binds

80
Q

What antibiotic should you avoid if you see macrolide resistance?

A

Clindamycin
(related to macrolides, so may be resistance)

YR5 Microbiology (23 decks)

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