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Year 5 - Pathology ICSM1 > Microbiology 2 - Antimicrobial agents 1 > Flashcards

Microbiology 2 - Antimicrobial agents 1 Flashcards

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

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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

Inhibits transpeptidase, which is an enzyme that forms cross links during the formation of the cell wall.
The resulting cell wall is therefore weak, and so the bacteria lyse because of osmotic pressure.

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6
Q

How does the cell wall of gram pos and gram neg bacteria differ?

A
  • Gram positive cell wall  very thick cell wall (made of NAG + NAM components)  purple
  • Gram negative cell wall  thin cell wall, outer membrane conferring resistance to some abx  pink
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7
Q

What bacteria is penicillin active against?

A

Gram pos

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8
Q

What bacteria is amoxicillin active against?

A

gram +ve, enterococci, gram -ve

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9
Q

Is streptococci gram pos or neg?

A

Gram pos

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10
Q

Which beta lactam antibiotic is effective against pseudomonas?

A

Piperacillin (a penicillin)

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11
Q

How can beta lactam resistance be overcome?

A

Include a beta lactamase inhibitor

Eg. Clavulanic acid + amoxicllin (in co-amoxiclav)

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12
Q

Is pseudomonas gram pos or gram neg?

A 
Gram neg
(Pseudo"moan"as - 'moan' = negative)
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13
Q

Is neisseria meningitis gram pos or gram neg?

A

Gram neg cocci

Neisseria starts with N = negative

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14
Q

Recall an antibiotic that is associated with C. difficile

A

Ceftriaxone (cephalosporin)

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15
Q

Which beta lactam antibiotics are stable to ESBL organisms?

A

Carbapenems

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16
Q

Recall a caution of beta lactam antibiotic

A

Excreted renally so reduce dose if renal impairment

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17
Q

What type of bacteria are glycopeptides effective against?

A

Gram pos only - they are large molecules so can’t penetrate gram neg cell wall

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18
Q

What are glycopeptides particularly useful for?

A

MRSA infection

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19
Q

What is a caution of glycopeptide antibiotics?

A

They are nephrotoxic + to some extent ototoxic

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20
Q

Recall the broad mechanism of action of glycopeptide antibiotics

A

Prevent peptide cross links in cell wall

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21
Q

Recall the broad mechanism of action of aminoglycosides

A

Bind to 30s ribosomal subunit, preventing elongation of polypeptide chain

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22
Q

Recall 2 examples of aminoglycoside antibiotics

A

gentamicin

amikacin

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23
Q

What type of bacteria are aminoglycoside antibiotics effective against?

A

Gram neg

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24
Q

Recall 2 toxicities of aminoglycosides

A

Ototoxicity

Nephrotoxicity

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25
Q

What type of bacteria are macrolides effective against?

A

Gram pos

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26
Q

What are macrolides particularly useful for?

A

Mild staph or strep infections in patients who are allergic to penicillin

27
Q

Recall 2 macrolide antibiotics

A

Azithromycin

Clarithromycin

28
Q

What type of bacteria are tetracylines effective against?

A

They are broad spectrum

Useful for intracellular pathogens- chlamydia

E.g doxy

29
Q

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

A

Tetracyclines

30
Q

Recall one side effect of tetracycline antibiotics

A

Light-sensitive rash

31
Q

Recall the broad mechanism of action of macrolides

A

Bind to the 50s subunit of ribosomes

32
Q

Recall the broad mechanism of action of tetracyclines

A

Bind to 30s subunit of ribosomes

33
Q

What type of bacteria is chloramphenicol effective against?

A

Many - it is v broad spectrum

34
Q

Why is chloramphenicol rarely used?

A

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

35
Q

Recall 2 specific bacteria that macrolides are effective against

A

Campylobacter sp
Legionella pneumophila
(macrolides = erythromycin/ azithromycin/ clarithromycin)

Useful agent for treating mild Staphylococcal or Streptococcal infections, particularly in penicillin-allergic patients
- Also active against Campylobacter sp and Legionella pneumophillia
o Although most campylobacter is self-limiting so usually don’t give treatment
o Given for atypical pneumonia due to other organisms such as mycoplasma

36
Q

Recall the broad mechanism of action of chloramphenicol

A

Binds to 50s subunit of ribosomes - inhibits formation of peptide bonds during translation

37
Q

Recall the broad mechanism of action of oxazolidinones

A

Binds to the 23s and 50s subunit of ribosomes to prevent 70s subunit formation

38
Q

Recall two types of bacteria that oxazolidinones (E.g Linezolid) are particularly active against

A

MRSA and VRE

MOA: Binds to 23S subunit of 50S, preventing the formation of 70S

Can cause thrombocytopenia

39
Q

Recall an example of oxazolidinones

A

Linezolid

40
Q

Recall one potential side effect of oxazolidinones

A

Thrombocytopaenia

41
Q

Recall the broad mechanism of action of fluoroquinolones (E.g ciprofloxacin)

A

Act on alpha subunit of DNA gyrase

42
Q

Recall 4 uses of fluoroquinolones

A

UTI
Pneumonia
Atypical pneumonia
Bacterial gastroenteritis

Gram -ve organisms
E.g ciprofloxacin

MOA: Act on alpha subunit of DNA gyrase

43
Q

Recall 3 examples of fluoroquinolone antibiotics

A

Levofloxacin
Moxifloxacin
Ciprofloxacin

44
Q

Give an example of a nitromidazole antibiotic

A

Metronidazole

45
Q

Recall types of organisms that metronidazole is effective against

A

Anaerobes

Protozoa

46
Q

When should nitrofurantoin be taken?

A

Right after visiting the toilet as it sits in bladder and is absorbed through the bladder, not systemically

47
Q

Recall the broad mechanism of action of rifampicin

A

Binds to DNA-dependent RNA polymerase to inhibit RNA synthesis

48
Q

Recall the main use of rifampicin

A

TB treatment

49
Q

Recall one side effect of rifampicin

A

Turns secretions orange

50
Q

Recall one condition of rifampicin prescription

A

Should never be prescribed alone as resistance develops very quickly (very important)

CYP450 inducer- so have to be careful about other drugs you are giving. E.g for COCP, you are advised not to take it and to take either IUS,IUD,Depoprovera instead, but if you are using COCP, double the dose.

51
Q

Colistin is very toxic. Why is it coming back into use?

A

It is active agianst certain multi-drug resistant bacteria

52
Q

What is daptomycin (Cell membrane toxin) licensed for the treatment of?

A

MRSA
VRE
Gram+ organisms

Linezolid (inhibits protein synthesis- binds 23s on 50s, preventing 70s) has same coverage

53
Q

Recall the 2 classes of antibiotic that inhibit folate synthesis

A

Sulphonamides (e.g sulfomethoxazole)
Diaminopyrimidines (e.g trimethoprim)

The combination of the two (co-trimoxazole/sulfomethoxazole-trimethoprim) is a valuable antimicrobial in certain situations (e.g. treating Pneumocystis jiroveci pneumonia)

54
Q

Give an example of a sulphonamide

A

Sulfamethoxazole

55
Q

What is the main use of trimethoprim

A

Uncomplicated/community acquired UTI

56
Q

What are the 4 main mechanisms of resistance

A
  1. Inactivation (eg beta latcamases)
  2. Altered target (so antibiotic no longer binds - important in MRSA where bacteria change the penicillin-binding protein, and in protein-synthesis inhibitors where the binding of the ribosome subunit is prevented)
  3. Reduced accumulation
    (most important in gram negs - either due to efflux or to reduced uptake)
  4. Bypass
    (particularly important for folate inhibitors - bacteria can change the enzyme they use)
57
Q

Which antibiotic is best for treating pseudomonas jirovecii?

A

Co-trimoxazole

58
Q

What is the broad mechanism of action of nirtromidazoles?

A

Inhibit DNA synthesis (Under anaerobic conditions, an active intermediate is produced which causes DNA strand breakage)

E.g Metronidazole, Tinidazole

Active against anaerobic bacteria and protozoa (e.g. Giardia)

59
Q

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

A

Staphylococcus

60
Q

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

A

Streptococcus

Strep sounds like ‘stripe’ = chain

61
Q

What gram stain status are enterococci?

A

Positive

“Enter-o-coccus” = like letting someone in, positive thing to do

62
Q

Is haemophilus gram pos or neg?

A

Gram neg

Ha”emo”philus - emo = negative

63
Q

Is listeria gram pos or neg?

A

Positive

Lister = good man = positive

Year 5 - Pathology ICSM1 (85 decks)

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