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Antimicrobials > Bact protein synthesis inhibitor > Flashcards

Bact protein synthesis inhibitor Flashcards

1
Q

Name 2 key targets of antimicrobials that work by inhibiting bacterial protein synthesis?

A

50S, 30S bacteria ribosomal subunits

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2
Q

Name at least 2 classes of antibiotics which are 30S protein synthesis inhibitors

A

tetracyclines, glycylcycline, aminoglycosides

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3
Q

Name 3 examples of tetracyclines

A

tetracycline, doxycycline, minocycline

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4
Q

Tetracycline prevents binding of ___________ to the A site of mRNA-ribosome complex
–> preventing protein synthesis

A

tRNA

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5
Q

Tetracyclines should not be administered with dairy products or substances that contain divalent and trivalent cations (antacids) as this would lead to the formation of ___________, which would ___________ the absorption of the drugs.

A

non-absorbable chelates,

reduce

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6
Q

Comment on tetracycline’s antimicrobial coverage

A

broad spectrum activity against many

  • Gram-negative
  • Gram-positive bacteria
  • atypical bacteria
  • spirochetes

EXCEPT Pseudomonas & proteus

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7
Q

How are tetracyclines cleared?

A

Tetracycline- renal

Doxycycline & minocycline - hepatic (hepatic dysfn req dose adjustments)

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8
Q

Which drug is used in community acq penumonia (eg H influ, S pneumoniae) & MRSA?

A

Doxycycline

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9
Q

How are tetracyclines administered?

A

Usually oral

IV only on special requests

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10
Q

Can tetracyclines be used in pregnancy?

A

No,
cross placenta
concentrate in places w high calcium content- fetal bone & dentition

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11
Q

How is glycylcycline (tigecycline) administered?

A

IV (poor bioavailability)

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12
Q

Glycylcycline (tigecycline) was designed to overcome which two mechanisms of tetracycline resistance?

A
  • Expression of efflux pumps

- Ribosomal protection (higher affinity to ribosome not easy to get dislodged by proteins)

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13
Q

Tigecycline is useful in targeting some of the resistant microbes including

A
  1. Methicillin resistant staphylococci (MRSA),
  2. Multidrug-resistant streptococci,
  3. Vancomycin-resistant enterococci (VRE),
  4. useful against carbapenem resistant strains of Extended-spectrum β-lactamase–producing gram-negative bacteria
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14
Q

What’s tigecycline not effective against?

A

pseudomonas + proteus (same as tetracycline)

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15
Q

How is tigecycline cleared?

A

Hepatic clearance– dose reduction for severe hep dysfn

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16
Q

Since tigecycline can treat resistant microbes, would it be a good option in bacteremia?

A

No, as tigecycline penetrates tissues well. Poor option for bloodstream infections.

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17
Q

Name at least 4 adverse effects associated with the use of tetracyclines & glycylcycline (tigecycline).

A
  1. Gastrointestinal distress (To reduce ulceration, drink plenty of fluids and do not take it before sleep)
  2. Phototoxicity (Like fluoroquinolones)
  3. Superinfection like thrush (fungal more common, CDAD only on prolonged use)
  4. Deposition in bone/primary dentition and may cause discoloration of teeth
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18
Q

The use of tetracycline and tigecycline is contraindicated in which populations of patients?

A
  1. Pregnant women,
  2. Breastfeeding women
  3. Children less than 7/8 years of age
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19
Q

What’s the difference b/n tetracycline VS aminoglycosides?

A

Tetracycline- bacteriostatic

Aminoglycosides- bacteriocidal (concentration dependent killing w PAE)

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20
Q

MOA of aminoglycosides

A

block formation of initiation complex, cause codon misreading, inhibit translocation

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21
Q

Aminoglycosides are transported across the inner membrane of Gram-negative bacteria by ___________ , which is an energy dependent process.

A

active transport

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22
Q

Aminoglycosides are particularly effective against _______ Gram-negative bacteria

A

aerobic

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23
Q

How is the action of aminoglycosides inhibited?

A

anaerobic conditions/ drop in pH

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24
Q

Name 5 examples aminoglycosides

A

gentamicin, streptomycin, tobramycin, amikacin, neomycin

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25
Q

Aminoglycosides demonstrate synergism when combined with which class of antibiotics? Name one class.

A

Beta lactams (e.g. gentamicin and ceftriaxone for the management of staphylococcus endocarditis)

as BL reduce cell wall and increase penetrance of aminoglycosides

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26
Q

Name an aminoglycoside that is used in the management of tuberculosis

A

Streptomycin (administered IM)

27
Q

How are aminoglycosides cleared?

A

Renally (dose adj required w renal imp)

28
Q

Indications of aminoglycosides

A
  1. Empiric therapy as broad spectrum– once pathogen isolated, discontinued and change to definitive tx
  2. Aerobic gram neg eg. pseudomonas
  3. Second line against MDR TB mycobacteria
29
Q

If patient has a CSF infection of xx, do you give aminoglycosides?

A

No, as [ ] in CSF inadequate even w inflamed meninges

30
Q

How are aminoglycosides commonly administered?

A

Parenterally (They have poor oral bioavailability)

31
Q

Name an aminoglycoside that is administered orally

A

Neomycin – Given oral for bowel prep for surgery

IV severe nephrotoxicity

(like vancomycin also poor oral bioav but given orally for CDAD)

32
Q

Which aminoglycoside has the widest spectrum?

A

Amikacin – but generally ineffective against anaerobic gram +ve strains

33
Q

Name at least 2 adverse effects associated with aminoglycosides

A
  1. **Ototoxicity
  2. **Nephrotoxicity
    * * do not combine w eg. vancomycin/amph B/NSAIDS
  3. Neuromuscular paralysis (Especially when used with neuromuscular blockers– contraind in MG)
34
Q

What are the 6 “NOs” in relation to aminoglycosides?

A
  1. No to protein synthesis
  2. Particularly active against aerobic Gram-“N”negative “O”rganisms
  3. No to use during pregnancy & myasthenia gravis
  4. No to oral administration
  5. No to CSF penetration
  6. “N”ephro- and “O”to- toxicities
35
Q

How can bacteria become resistant to aminoglycosides?

A
  1. efflux pump
  2. amgs inactv enzymes
  3. alter 30 S ribosome
  • note so antibiotics don’t affect humans as 60S 40S
36
Q

Name 3 types of 50S protein synthesis inhibitors

A

Macrolides, clindamycin, linezolid

37
Q

Name 3 macrolides

A

Erythromycin, clarithromycin, azithromycin

38
Q

Are macrolides bacteriostatic or bactericidal antibiotics?

A

Bacteriostatic

39
Q

Which of the macrolides cause the most GI distress?

A

Erythromycin

:( as also inhibit CYP 450 hence DDI

40
Q

How can macrolides be administered?

A

Oral and IV

41
Q

Name some of the microbial infections that the macrolides are useful against

A
  • common sub for penicillin allergy
  1. *Atypicals (Mycoplasma, chlamydia, legioella)
  2. *Community acquired penumonia (S.pneumoniae, H. influenzae and Moraxella catarrhalis)
  3. STDs caused by Chlamydia trachomatis and Neisseria gonorrhoea
  4. *H.pylori infections (clarithro> azithro)
42
Q

How are macrolides cleared?

A

Erythromycin and clarithromycin undergoes hepatic clearance (contraind hepatic dysfn)

Azithromycin – is mainly eliminated unchanged in faeces

43
Q

Name 2 adverse effects associated with macrolides.

A
  1. Gastric Distress
  2. Hepatotoxicity
  3. Ototoxicity
  4. May prolong QT interval (aware if pt pro-arrthy)
44
Q

Which drugs are useful in pregnancy?

A
  1. Beta lactams (penicillins)
  2. Macrolides (erythromycin & azithromycin)
  3. Clindamycin
45
Q

Name 2 mechanisms via which bacteria may acquire macrolide resistance

A

ERM gene expression, efflux pumps

erythromycin methylase- ribosomal methylation, reduced binding

46
Q

Which drug(s) can exhibit cross resistance with macrolides?

A

Clindamycin (if the microbes acquire resistance by expressing **erm methylases)

*thus if resistant to macrolide don’t give clindamycin

BUT if pt macrolide resistance due to efflux pump, can give clindamycin

47
Q

Clindamycin is primarily used to treat _________ infections

48
Q

What shld not be given w clindamycin?

A

Macrolides– antagonistic effect

49
Q

How is clindamycin administered?

50
Q

Name an adverse effect associated with the use of clindamycin

A

Clostridium difficile associated diarrhoea

**highest risk!! (cannot use for CDAD)

51
Q

Can clindamycin be used to treat MRSA?

52
Q

What drugs can be given for MRSA?

A
  1. 5th gen cephalosporin (ceftobiprole/ceftaroline) IV
  2. vancomycin IV
  3. tigecycline IV
  4. clindamycin oral
  5. linezolid oral
  6. doxycycline oral/(IV special req)
53
Q

Name 2 antibiotics that can be administered orally for MRSA

A

Linezolid and clindamycin

54
Q

Indications for clindamycin

A
  1. pencillin resistant *ANAEROBIC eg bacteroides (w cefotetan, cefoxitin), clostridium perfringen
    = good oral formulations **
  2. Gram +ve *MRSA/strep
  3. EXCEPT aerobic gram -ve + CDAD
55
Q

Linezolid works by ___________

A

It binds the bacterial 23S ribosomal RNA of the 50S subunit and inhibits the formation of the initiation complex needed for protein synthesis.

56
Q

Linezolid is effective against Gram _________ bacteria?

57
Q

Name 3 antibiotics that only covers Gram positives?

A

Vancomycin, penicillinase resistant penicillin, linezolid

58
Q

How is linezolid administered?

59
Q

What does linezolid cover?

A

Many of the resistant Gram-positive strains such as MRSA, VRE, VRSA

EXCEPT gram -ve

** only use if alternatives exhausted – LAST LINE

60
Q

How is linezolid excreted?

A

nonenzymatic oxidation to inactive metabolites– no need adj dose in renal imp

61
Q

Name at least 2 key adverse effects associated with prolonged use of linezolid

A
  1. Irreversible peripheral neuropathies
  2. Optic neuritis (>28d dose)
  3. Bone marrow suppression (>10d)
62
Q

Linezolid can cause _________ if administered concomitantly with SSRI or MAO inhibitors?

A

serotonin syndrome

63
Q

Can linezolid be used for the treatment of *catheter-related bloodstream infections?

A

No, it is not approved. (Based on FDA recommendation)

64
Q

Linezolid resistance

A

mutation of 23S ribosome

Antimicrobials (11 decks)

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