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Respiratory Medicine Midterm > Protein Synthesis Inhibitors - 30S ribosome > Flashcards

Protein Synthesis Inhibitors - 30S ribosome Flashcards

1
Q

Amikacin

A

For gentamicin resistant organisms

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2
Q

Gentamicin

A

gram (-) aerobic

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3
Q

Kanamycin

A

Worst nephro- and oto- toxicity, only for TB and topical

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4
Q

Neomycin

A

Topical use

bowel sterilization

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5
Q

Streptomycin

A

Primarily for mycobacterial tuberculosis in hospital setting

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6
Q

Tobramycin

A

Pseudomonas aeruginosa

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7
Q

Treatment of Brucellosis

A

Gentamicin + doxycycline

cow vector

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8
Q

Treatment of Tularemia

A

Gentamicin
Tetracycline is effective as alternative

Rabbit vector

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9
Q

Treatment of Yersinia pestis

A

Streptomycin + doxycycline

Rat vector

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10
Q

Treatment of Pseudomonas Aeruginosa

A

Tobramycin* + pipericillin or ticarcillin

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11
Q

Treatment of Klebsiella

A

Gentamicin + pipericillin or ticarcillin

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12
Q

Pathogenic Gram Negative Rods

A 
Escherischia
Enterobacter
Serrate
Pseudomonas
Acinetobacter
Klebsiella
Yersinia pestis
Brucella
F. tularensis
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13
Q

MOA of aminoglycosides

A

Passive diffusion through porins

O2 dependent active transport ot cytosol (must have O2, not anaerobic)

Bind to 30S ribosomal unit- irreversible, bactericidal, post-antibiotic effect

Disrupt protein synthesis - reading errors

Irreversible bactericidal effects

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14
Q

Gentamicin properties

A

Strong base, positive charge, water soluble

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15
Q

Mechanism of Resistance or aminoglycosides

A

Depletion/deficit of porins (MDR)

O2 deficit/anaerobic organisms

Enzymatic alteration of amino glycoside structure, impairs binding to 30S ribosomal unit and/or cell entry

  • acetylation
  • phosphorylation
  • adenylation

Mutation of 30 s ribosome

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16
Q

Anaerobes intrinsically resistant to aminoglycosides

A

Gram + rods - clostridia

Gram - rods- Bacteroides, Fusobacteria

17
Q

Amino glycoside dosing

A

total daily dose administered as single injection

Associated with less toxicity, equal efficacy compared to multiple dose regimens

Trough determines safety as level drops below toxic threshold, TID dosing causes drug to accumulate in ear

18
Q

Pharmacokinetics

A

highly polar, poorly absorbed from GI tract, rapidly absorbed after IM (peak 60-90 min)

Do not penetrate eye or CNS

Eliminated by glomerular filtration with half life of 2-3 hrs

Accumulate in renal cortex, inner ear perilymph damaging hair cells = nephrotoxic and ototoxic

19
Q

Renal toxicity of aminoglycosides

A 
Risk factors:
Low BP
Loop diuretics (furosemide)
Advanced age
Other nephrotoxic agents - cyclosporin in transplant patients, amphotericin in severe fungal infections
20
Q

Neuromuscular blockade by aminoglycosides

A

Risk greatest with intra-pleural and intra-peritoneal administration or large doses or rapid IV infusion
-can produce apnea or respiratory arrest

may aggravate or reveal myasthenia graves or cause transient myasthenia syndrome

Managed with neostigmine or ventilator in extreme cases

21
Q

Properties of tetracycline

A

Potency: low

Intestinal absorption: moderate

Disrupt Gut: high

Phototoxic: low

22
Q

Properties of Demeclocycline

A

Potency: Med

Intestinal absorption: Moderate

Disrupt Gut: Moderate

Phototoxic: Worst

23
Q

Properties of Minocycline

A

Potency: high

Intestinal absorption: complete, little food interference

Disrupt Gut: least

Phototoxic: high

Reaches therapeutic levels in CNS for meningeal carriers

24
Q

Doxycycline properties

A

Potency: high

Intestinal absorption: complete, little food interference

Disrupt Gut: least

Phototoxic: high

Preferred agent parenterally, preferred with renal impairment

25
Q

Tigecycline properties

A

phototoxic

Overcomes resistance and MRSA

26
Q

Uses of Doxycycline for unusual organisms

A

Rickettsial infections (intracellular) - Rocky Mtn spotted fever, Q fever, typhus

Borrelia burgdorferi (Spirochete) - Lyme disease

Chlamydia trachomatis - Major STD - urethritis (non-specific), pelvic inflammatory disease, Lymphogranuloma venereum

Chlamydia psittaci - psittacosis pneumonia

Mycoplasma pneumonia - young adults, close quarters (alternate - erythromycin)

Vibrio cholera - Cholera - single dose doxy

27
Q

MOA of Tetracyclines

A

Passive diffusion into bacterial cytosol

Bind to 30 S ribosomal unit - bacteriostatic, reversible - inhibits rate of protein synthesis

Block binding of aminoacyl-tRNA

Inhibit protein synthesis

Exert bacteriostatic effects

28
Q

Mechanisms of resistance of tetracyclines

A

Tetracycline efflux pump - acquired - plasmid encoding Tet A efflux pumps, bacteria thrive with ribosome intact

Ribosome protection (methylation of ribosome) - plasmid encoding protecting protein, chromosome encoding protecting protein, bacteria thrive with ribosome intact

29
Q

Distribution of tetracyclines

A

Good entry into most body fluids and compartments

Cross placenta

Enter CNS - seldom reach CNS levels adequate for therapeutic efficacy

Minocycline exception - used to eliminate meningococcal carrier state

30
Q

Metabolism and excretion of tetracyclines

A

Phase 2 conjugation - glucuronide metabolites

Biliary secretion of parent drugs and metabolites

Undergo enterohepatic recirculation

Doxycycline - safe for renal impairment - only oe

31
Q

Adverse Effects of Tetracyclines

A

GI disturbance - superinfection; Ca2+ and Mg2+ antacids and dairy foods interfere with absorption - irritates mucosa, cause epigastric distress

Accumulation in teeth and bone - chelates Ca2+ and Mg2+; contraindicated in under 8 yo

Fatal hepatotoxicity - fatty liver, especially during pregnancy

Phototoxicity

Vestibular problems - minocycline

Diabetes insipidus - demeclocycline

32
Q

Tetracycline and the mitochondrial ribosome

A

Concentrate in liver, enter hepatocytes

disrupt metabolic pathways leading to excessive lipid production and deposition in liver

especially problematic in pregnancy

33
Q

Complications with Tetracyclines in pregnancy

A

Deposit in teeth and bone

Fatty liver deposition in pregnancy can lead to fatal hepatitis

Contraindicated in pregnancy and breast feeding and children under 8 yo

34
Q

Tetracycline association with superinfections

A

Loss of commensal enteric bacteria

C. difficile thrives

Pseudomembranous colitis occurs - can be life threatening

35
Q

Tigecycline

A

Structural modifications of minocycline improves spectrum of activity

No drug interactions, biliary excretion

Safe in patients with renal impairment

Decreased susceptibility to resistance by tet A efflux pumps and ribosomal protection

36
Q

Spectrum of activity of Tigecycline

A

Gram + aerobes including MRSA, VRE

Gram -

Anaerobes - Clostridium perfringens, Bacteroides sp.

Respiratory Medicine Midterm (11 decks)

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