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Multisystems: Pharmacology > Bacterial Protein Synthesis Antibiotics > Flashcards

Bacterial Protein Synthesis Antibiotics Flashcards

1
Q

Which drugs inhibit the formation of the initiation complex?

A

Aminoglycosides (30s) and Linezolid (50s)

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2
Q

Which drugs inhibit amino acid incorporation?

A

Tetracyclines (30s)

Dalfopristin/quinupristin (50s) aka Streptogramins

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3
Q

Which drug inhibits formation of the peptide bond?

A

Chloramphenicol (50s)

Specifically, it inhibits the enzyme peptidyl transferase

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4
Q

Which drugs inhibit translocation?

A

Macrolides and Clindamycin (50s)

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5
Q

What reads mRNA?

A

Ribosomes

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6
Q

Where does tRNA bind during bacterial protein synthesis?

A

The “P” or “A” site (the P site is only bound to once, during initiation)

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7
Q

What is the initiating AA (aka which AA contains the AUG codon)?

A

Formyl methionine

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8
Q

What is a unique property of formyl methionine?

A

Chemokine for neutrophils and macrophages

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9
Q

Why are aminoglycosides bacteriocidal while Linezolid is bacteriostatic?

A

Aminoglycosides cause a shift in the reading frame and the incorporation of the wrong AA (think steric hindrance)

Linezolid inhibits the formation of the initiation complex by preventing the formation of the N-formylmethionyl-tRNA-ribosome-mRNA ternary complex

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10
Q

Activity of Aminoglycosides

A

Bactericidal, accumulated intracellularly in microorganisms via an O2-dependent uptake (anaerobes are innately RESISTANT)

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11
Q

What are Gentamicin, Tobramycin, and Amikacin used for?

A

Useful against gram-negative rods

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12
Q

Synergistic actions of aminoglycosides

A

Enterococci = aminoglycosides + penicillin G

P. aeruginosa = aminoglycosides + extended spectrum penicillin or 3rd generation cephalosporin

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13
Q

Streptomycin

A

Aminoglycoside used in TB and is DOC for bubonic plague

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14
Q

Resistance to aminoglycosides

A

Innate = anaerobes

Production of conjugating enzyme = eliminated too fast

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15
Q

Pharmacokinetics of aminoglycosides

A

Glyco = Sugar = Water soluble

Polar compounds (i.e., not absorbed orally or widely distributed into tissues)

Renal elimination (major dose reduction needed in renal dysfunction)

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16
Q

Side effects of aminoglycosides

A
  1. Nephrotoxicity
  2. Ototoxicity
  3. Neuromuscular blockade (decreased ACh)
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17
Q

What are the components of triple antibiotic ointment?

A
  1. Neomycin
  2. Polymyxin
  3. Bacitracin

*Neomycin is the component that leads to contact dermatitis

18
Q

Explain One-Daily Dosing of Aminoglycosides

A

Antibacterial effects depend mainly on “peak drug level” and not “time”

The effects of aminoglycosides continue even when blood levels of the drug drop below the MIC (aka PAE)

(Toxicity depends on blood level and the time that such levels are > than a specific threshold)

MIC = minimum inhibitory concentration

PAE = post-antibiotic effect

19
Q

Activity and clinical uses of tetracycline

A

Bacteriostatic drugs, actively taken up by susceptible bacteria

“broad spectrum” antibiotics with good activity versus chlamydial and mycoplasmal species, H pylori, Rickettsia, Borrelia burgdorferia…

Backup drug for treponema

20
Q

Doxycycline

A

DOC in lyme disease (Borrelia burgdorferi)

Lipid soluble

Useful in prostatitis (from chlamydia or n. gonorrhea) because it reaches high levels in prostatic fluid

21
Q

Minocycline

A

Water soluble Tetracycline

In saliva and tears (good for gingivitis) at high concentrations and used in the meningococcal carrier state

22
Q

Demeclocycline

A

Tetracycline used in SIADH (blocks ADH receptor function)

23
Q

Why can’t you take tetracyclines with your meals?

A

They are Chelators

aka they bind divalent cations (Ca2+, Mg2+, Fe2+) which decreases their absorption

aka DO NOT take with food

24
Q

Resistance to tetracyclines

A

Pumps (p. glycoprotein)

25
Q

Side effects of tetracyclines

A
  1. Tooth enamel dysplasia
  2. Phototoxicity
  3. GI distress
  4. Vestibular dysfunction (minocycline)
  5. Liver dysfunction during pregnancy

***Contraindicated in children (b/c it decreases bone growth) and in pregnant women

26
Q

Activity and clinical uses of Chloramphenicol

A

Bacteriostatic with a wide spectrum of activity

“phen” = lipid soluble = (1) crosses BBB, (2) metabolized in the liver, (3) not contraindicated in renal dysfunction

27
Q

pharmocokinetics of chloramphenicol

A

Orally effective with good tissue distribution (including CSF)

Metabolized by hepatic glucuronidation (dose reduction required in liver dysfunction and in neonates)

Inhibition of cP450

28
Q

Side effects of chloramphenicol

A

Dose-dependent bone marrow suppression (aplastic anemia)

-similar to anticancer agents

“gray baby” syndrome in neonates (decreased glucuronosyl transferase)

-toxic and diplaces bilirubin

29
Q

Which drugs are contraindicated in pregnancy?

A
  1. Aminoglycosides
  2. Fluoroquinolones
  3. Sulfonamides
  4. Tetracyclines

Pregnant people are F.A.T.S.

30
Q

Which 3 drugs are notorious for phototoxicity?

A
  1. Tetracylines
  2. Sulfonamides
  3. Quinolones

Toxic Sun Quilts Skin

31
Q

What type of drugs are Erythromycin, Azithromycin, and clarithromycin?

How do they work?

(HINT: all have “thro” in their name)

A

Macrolides: wide-spectrum antibiotics that inhibit translocation

Gram (+) cocci [not MRSA], atypical organisms, campylobater, MAC (need a “mac” for MAC), H pylori

DOC for legionella pneumophilia

Atypicals = Chlamydia, Mycoplasma, and Ureaplasma

32
Q

Telithromycin

A

a ketolide active against macrolide-resistant S. pneumonia

33
Q

Side effects of macrolides

A
  1. Stimulate motilin receptors and cause GI distress
  2. Reversible deafness
  3. Increased QT interval

(Eat a big MAC = GI distress…if you don’t listen to how bad fast food is = heart attack)

34
Q

Resistance to Macrolides

A

Methyltransferases (cannot recognize 50s binding site)

35
Q

Why are macrolides commonly used to treat community acquired pneumonia (atypical)

A

Most common organisms responisble are m. pneumoniae and c. pneumoniae (in smokers, pneumococcus are more frequently the pathogen)

Macrolides have activity against most strains of these organisms (other than viruses)

36
Q

Clindamycin

A

Not a macrolide, but has the same MOA and resistance

Narrow spectrum: gram (+) cocci [including MRSA], anaerobes [backup drug for B fragilis]

Clinical value in osteomyelitis (which is often caused by Staph aureus)

37
Q

Side effect of Clindamycin

A

Pseudomembranous colitis

(treated with metronidazole)

38
Q

Spectrum for Linezolid

A

Treatment of VRSA, VRE, and drug-resistant pneumococci

39
Q

Side effect of Linezolid

A

BM suppression (platelets)

40
Q

MOA of quinupristin-dalfoprisitin

A

Streptogramins that act in concert via several mechansims:

BLUF = block AA incorporation

  1. binding to sites on 50s, they prevent interaction of amino-acyl-tRNA with acceptor site and stimulate its dissociation
  2. decrease the release of completed polypeptide by blocking its extrusion
41
Q

Spectrum for streptogramins

A

Used parenterally in severe infections caused by VRSA and VRE, as well as other drug-resistant gram (+) cocci

42
Q

Difference between streptogramins and linezolid

A

Streptogramins are used for E faecium but not for E faecalis

Linezolid is used for both types of enterococci

Multisystems: Pharmacology (11 decks)

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