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Pathology > M - Antimicrobials > Flashcards

M - Antimicrobials Flashcards

1
Q

Most common systems affected in adverse reactions to ABx

A

GI upset
Rash
Renal dysfunction
Anaphylaxis!!
Hepatitis

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2
Q

Name 2 Abx commonly causing renal dysfunction

A

Gent + Vanc

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3
Q

4 things to consider when choosing an abx for an individual

A
  • Host characteristics (age? disease?)
  • Antimicrobial susceptibilities
  • Organism
  • Site of infection
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4
Q

Methods of identifying infecting organism?

A

Gram stain: from CSF, pus, joint aspirate

Immunofluorescence or PCR to identify an antigen rapidly

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5
Q

What clinical features of a patient would make you consider using an Abx?

A

systemic response: fever, neutrophilia (neutropenia in severe infection), raised CRP

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6
Q

When to switch from IV to po?

A

After 48 hours if pt has stabilised

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7
Q

3 patterns of Abx activity

A
  1. Concentration dependent killing (max concentration of drug)
  2. Time dependent killing (time that drug conc’n is above MIC)
  3. Both
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8
Q

Concentration-dependent Abx?

A

Aminoglycosides

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9
Q

Time-dependent abx?

A

penicillins

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10
Q

Recommended time of abx course for simple cystitis? gp a strep throat?

A

3 days - cystitis
10 days - strep throat

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11
Q

N. meningitidis meningitis - length of abx course?

A

7 days

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12
Q

Length of abx course for bacterial endocarditis? for acute osteomyelitis?

A

IE: 4-6 weeks
osteomyelitis - 6 weeks

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13
Q

Typical Abx for cellulitis/

A

flucloxacillin unless allergic or MRSA. MRSA –> vancomycin

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14
Q

Typical Abx for pharyngitis? how long for?

A

Benzylpenicillin for 10 days

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15
Q

Typical Abx for CAP - mild and severe?

A

mild = amoxicillin
severe = coamoxiclav + clarithromycin

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16
Q

Typical Abx for HAP?

A

amoxicillin + gentamicin or tazocin

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17
Q

typical antibiotic for bacterial meningitis?
What is the exception?

A

Ceftriaxone
Or amoxicillin if young/old/immunocomp due to risk of listeria

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18
Q

typical Abx for UTI - community? hospital?

A

community = trimethoprim
Nosocomial = co-amoxiclav/cephalexin

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19
Q

Typical Abx for Sepsis - severe?

A

Ceftriaxone/tazocin, metronidazole +/- Gentamicin

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20
Q

Typical Abx for Neutropenic sepsis?

A

Tazocin + gentamycin

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21
Q

Typical Abx Mx for C-difficile colitis

A
  • STOP the cephalosporins!!!
  • Start with metronidazole PO.
  • If ineffective, use vancomycin
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22
Q

3 types of beta lactams

A

pencillins
cephalosporins
carbapenems

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23
Q

Name 4 penicillins and state what they vs

A

1) penicillin
2) amoxicillin - also cover enterococci + E. Coli!!!!
3) flucloxacillin - resistant to b-lactamases
4) piperacillin - also against pseudomonas + non-GI gram -ves

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24
Q

2 useful things to use with Abx?

A

clavulanic acid and tazobactam

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25
Q

How do the cephalosporins change from 1st –> 3rd gen?

A

Increased Gram -ve activity

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26
Q

Which cephalosporin is 2nd gen?

A

Cefuroxime

27
Q

Which cephalosporin is assoc. with C. Difficile?

A

Ceftriaxone

28
Q

Name the cephalosporin which covers Pseudomonas? which bacteria does it not cover?

A

Ceftazidime! Doesn’t cover any Gram +ve

29
Q

Why were carbapenems developed?

A

bacteria developed extended spectrum beta lactamases, therefore resistant to cephalosporins

30
Q

Name some carbapenems? Which things are resistant to them now?

A

Merapenem, Ertapenem
- MDR klebsiella, MDR acinetobacter

31
Q

Advantages of using b-lactams?

A

Short half life
Relatively non-toxic
Doesn’t cross the BBB

32
Q

Which cell wall synthesis inhibitors cannot be used against Gram-ves?

A

Glycopeptides - can’t penetrate the gram -ve cell wall

33
Q

Name 2 glycopeptides

A

vancomycin, teicoplanin

34
Q

What are glycopeptides particularly useful vs?

A

MRSA, C. Difficile, enterococci

35
Q

What type of Abx is gentamicin?
MOA?

A

Amino glycosides!
Binds to 30S ribosomal subunit - inhibits elongation of pp chain + causes misreading of codons from mRNA.
Conc’n dependent

36
Q

What are aminoglycosides particularly useful vs?

A

Neutropenic gram -ve sepsis, Pseudomonas

37
Q

Doxycycline - which Abx class is it in? What is it useful against?

A

Tetracyclines
Intracellular organisms - chlamydiae, rickettsiae, mycoplasmas

38
Q

Special considerations with tetracyclines?

A

Don’t give to children + pregnant women
- Causes a light sensitive rash

39
Q

Name 3 macrolides.

A

Erythro/clarithro/azithromycin

40
Q

MOA of macrolides

A

Bind to 50S ribosomal subunit

Interfere with translocation

41
Q

Usefulness of macrolides vs?

A

Against strep/staph if penicillin allergic
Campylobacter, Legionella (CAP)
S. Typhi (w azithromycin)

42
Q

Chloramphenicol - why isn’t it used much?
How is it used now - give 2 uses?
MOA?

A
  • Risk of aplastic anaemia + grey baby syndrome
  • Bacterial conjunctivitis + meningitis if pen-allergic
  • Binds to 50S ribosomal subunit - inhibits translation
43
Q

Linezolid - MOA?

A
  • ## Prevents formation of 70S initiation complex
44
Q

What type of bacteria can Linezolid be used againt?
2 examples of bacteria which work especially well

A

GRAM +VES ONLY
esp MRSA + VRE

45
Q

Quinolone - eg? MOA?

A

Ciprofloxacin, levofloxacin

Binds to alpha subunit of DNA gyrase

46
Q

Quinolones - 2 bacteria it is used against?

A

pseudomonas + chlamydia

47
Q

Eg of nitroimidazoles?

A

metronidazole

48
Q

2 useful groups which metronidazole is used against? give eg of each?

A

Protozoa and Anaerobes
Giardia + C Diff.

49
Q

Name an RNA synthesis inhibitor?

A

RIfampicin

50
Q

What does rifampicin bind to? what precautions must be taken - name 4

A

Binds to DNA dependent RNA polymerase
- MONITOR LFTs
- single a.a. change –> resistance therefore NEVER use alone
- Turns secretions orange
- DDIs - eg COC

51
Q

name 2 cell membrane toxins

A

Daptomycin + Colistin.

52
Q

When is colistin used? SE?

A

Last line for MDR- bacteria. eg klebsiella, acinetobacter, pseudomonas
- last line as it is nephrotoxic!

53
Q

Name some useful folate metabolism inhibitors and what they’re used against

A

Co-trimoxazole - PCP
Trimethoprim - community UTI

54
Q

4 mechanisms of Abx resistance

A

BEAT
Bypassing Abx-sensitive step of pathway
Enzyme mediated inactivation of Abx
Accumulation impairment (efflux of abx from cell)
Target alteration

55
Q

2 main modes of resistance against beta lactams?

A

Enzyme mediated inactivation - beta lactamases
Target alteration - mecA gene by MRSA and PBP mutation in pneumococcus

56
Q

Give e.g.s of 2 bacteria which have altered their target to become resistant to beta-lactams?

A

MRSA - mecA gene = encodes a novel PBP 2a

Pneumococcus - multiple PBP gene mutations

57
Q

Macrolides - how have bacteria become resistant to them?

A

Erm gene encode for target alteration –> reduced binding of macrolides

58
Q

Good prophylactic Abx for splenectomy patients against S. pneumonia?

A

Amoxicillin

59
Q

2 major side effects of amoxicillin

A

Anaphylaxis
Steven Johnsons

60
Q

Trimethoprim: MOA?

A

Folate antagonist

61
Q

3 side effects of trimethoprim

A
  • Megaloblastic anaemia
  • Low platelets
  • Hyperkalemia (by inhibiting DCT Na channels)
62
Q

Abx against N. meningitidis

A

Cefotaxime

63
Q

MOA of vancomycin

A

Glycopeptide which inhibits cell wall synthesis

64
Q

What precautions are taken when giving vancomycin and why?

A

Vancomycin serum levels need to be monitored when given due to extensive side effects:

  • Kidney failure
  • Ototoxicity
  • Anaphylaxis
  • Blood disorders
  • Rash

Pathology (87 decks)

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