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ID Review > B&B Protein Synthesis Inhibitors > Flashcards

B&B Protein Synthesis Inhibitors Flashcards

1
Q

Protein Synthesis Inhibitors

A 
Aminoglycosides
Macrolides
Tetracyclines
Chloramphenicol
Clindamycin
Linezolid
Streptogramins
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2
Q

Bacterial Protein Synthesis

A

DNA inside cytoplasm which must be transcribed to RNA by RNA polymerase (target of Rifampin for tuberculosis)

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3
Q

To initiate protein synthesis

A
  1. Initiate Process: Ribosomal subunits have to bind mRNA
    - 50s subunit and 30s subunit
  2. Add tRNA
  3. Add peptides, translocate
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4
Q

Antibiotics that work on initiation process

A

Aminoglycosides/Linezolid

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5
Q

Antibiotics that block tRNA addition

A

Tetracyclines

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6
Q

Antibiotics that block addition of peptides and translocation

A

Chloramphenicol
Macrolides
Clindomycin

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7
Q

Aminoglycosides

A 
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
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8
Q

Aminoglycosides

A

Block protein synthesis initiation

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9
Q

Aminoglycoside MOA

A

Block initiation of protein synthesis

  • Primarily bind 30S
  • Misreading of genetic code
  • Bacteria cannot divide, produce cellular proteins
  • Cell death (bactericidal)
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10
Q

Aminoglycosides require what for transport into cells

A

O2

Not effective against anaerobes

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11
Q

Do aminoglycosides affect eukaryotic cells?

A

No (different ribosomes)

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12
Q

Are aminoglycosides transported into eukaryotic cells?

A

No. Therefore they are not effective against IC organisms like Rickettsia and Chlamydia

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13
Q

Aminoglycosides are usually used

A

in combination but can be used along for serious gram (-) infections

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14
Q

Streptomycin

A

Aminoglycoside used for tuberculosis in combo w/ other drugs

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15
Q

Neomycin

A

Given prior to bowel surgery
Poorly absorbed (stays in gut)
Often given with erythromycin
Decrease colonic bacteria

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16
Q

Aminoglyosides are often added to what drug

A

Beta-lactams

Synergistic effects: Combo effective than one drug alone

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17
Q

Endocarditis Tx

A

Vancomycin/Gentomycin

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18
Q

Newborn meningitis Tx due to Listeria

A

Ampicillin/Gentamycin

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19
Q

Pseudomonas Tx for CF patients

A

Pip/Tazo + tobramycin

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20
Q

Resistance to aminoglycosides

A

Bacteria acquire Aminoglycoside Modifying Enzymes
Bacteria acquired enzymes that modify drug structure
Modified structure binds poorly to ribosomes
Phosphorylation (mediated by aminoglycoside kinase)
Adenylation/acetylation (mediated by transferases)

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21
Q

Aminoglycosides: Adverse S/E

A 
Ototoxicity: 8th CN
-Hearing loss, balance problems
Nephrotoxicity:
-5-10% of drug taken up by proximal tubule cells
-Serum creatinine will rise
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22
Q

Rare S/E of aminoglycosides

A

Neuromuscular blockade

  • Can limit/block release of Ach at NMJ
  • Usually occurs when levels are high or pre-existing neuromuscular disease
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23
Q

Can you give aminoglycosides to pregnant women?

A

No. Pregnancy Class D. Renal and Ototoxicity in fetus.

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24
Q

Aminoglycosides: plasma level monitoring

A

Trough level: just before next dose

Peak level: short time after dose

25
Q

High aminoglycoside trough =

A

High risk for toxicity

26
Q

Low aminoglycoside peak =

A

Less effective therapy

27
Q

Macrolides

A

Azithromycin, Clarithromycin, Erythromycin

28
Q

MOA Macrolides

A

Bind 50s ribosomal subunit and block process of translocation:
tRNA binds A site
Ribosome RNA catalyzes peptide bonds (peptidyl transferase)
Ribosome advances along mRNA
tRNA moves to P site
Block tRNA movement to P site (translocation)
Promote tRNA dissociation
May also block peptidyl transferase

29
Q

Macrolides

A

Cover many gram (+) cocci, especially strep
Some gram (-) coverage
Concentrated inside macrophages, other cells
Effective against IC pathogens
-Chlamydia (obligate)
-Legionella (facultative)

30
Q

Common uses of Macrolides

A

Community Acquired Pneumonia
-Azithromycin covers Strep, H. flu, Atypicals
-Good for penicillin allergic patients
Chlamydia Infections
-Azithromycin (safe in pregnancy)
-Often co-administered with Ceftriaxone (gonorrhea)

31
Q

Erythromycin

A

Macrolide
Binds to motolin receptors in GI tract
Stimulates SM contraction
Can be used in GI motility disorders

32
Q

Clarithromycin

A

Part of triple therapy for H. pylori

33
Q

Macrolide Resistance

A

Bacteria methylate location of macrolide binding, which is 23S rRNA = component of 50S ribosome

34
Q

Macrolides: Adverse Effects

A

Nausea, diarrhea, abdominal pain (motility)
-Erythromycin is worst offender
Prolonged Qt on EKG (prolonged K+ blocking)
-Erythromycin is also worst offender
Acute cholestatic hepatitis
-Increased AST/ALT/Alk Phos (out of proportion)/Bilirubin
-Case reports with Azithromycin
-Contraindicated with h/o cholestatic jaundice or hepatic dysfunction
Rash
-Maculopapular allergic reaction

35
Q

P450 enzyme inhibitors

A

Will raise serum levels of P450 metabolized drugs

Theophylline, Warfarin

36
Q

Tetracyclines

A

Tetracycline, Doxycycline, Demeclocycline, Minocycline

37
Q

Tetracyclines MOA

A

Transported into bacterial cells
Binds 30S ribosome
Prevents attachment of tRNA

38
Q

Demeclocycline

A 
Tetracycline
Not used as an antibiotic
ADH antagonist
Given in SIADH
Causes nephrogenic DI to reverse SIADH
39
Q

Doxycycline

A

Most commonly used member of tetracycline family
Accumulates IC
Covers many unusual/atypical bacteria
-most zoonoses
-chlamydia
Acne Vulgaris Tx (also minocycline)
-Covers propionibacterium acnes in follicles

40
Q

Tetracyclines

A 
Absorption impaired by minerals and antacids
Cations chelate drug
-Calcium, magnesium (antacids)
-Iron
-Dairy
41
Q

Tetracyclines resistance

A

Decreasing influx or increasing efflux from cells
Plasmid-encoded transport pumps
Different from many other antibiotics
-No alteration of drug by bacteria

42
Q

Tetracycline Adverse Effects

A

GI distress (common)
-Epigastric pain, N/V, anorexia
Photosensitivity
-Red rash or blisters from sun

43
Q

Tetracycline Adverse Effects

A

Discolors teeth of children

Inhibits bone growth in children due to calcium chelation

44
Q

Can you use tetracyclines if you are pregnant?

A

No. They cross placenta and accumulate in fetus bones and teeth.

45
Q

Chloramphenicol

A

Inhibits peptidyl transferase:
50s ribosomal subunit
-tRNA binds A site
-Ribosome RNA catalyzes peptide bonds (peptidyl transferase)
-Ribosome advances along mRNA
-moves tRNA to P site
Chloramphenical blocks peptidyl transferase

46
Q

Chloramphenicol is rarely used due to

A

toxicity and resistance

47
Q

Chloramphenical

A

Broad coverage of gram (+), gram (-) and atypicals
Can be used in pregnancy instead of doxycycline
-Rickettsia (RMSF), Ehrlichia
-Only in 1st/2nd trimester
-3rd trimester: gray baby syndrome

48
Q

Chloramphenical

A

Used for meningitis

  • Covers Neisseria
  • less effective than alternative drugs
49
Q

Chloramphenical Adverse Effects

A

Anemia: bone marrow suppression

Aplastic anemia: Idiosyncratic, Irreversible, fatal

50
Q

Gray baby syndrome

A 
Babies lack liver UDP-glucuroynyl transferase
Required for drug metabolism/excretion
Skin turns ashen, gray
Hypotension
Often fatal
51
Q

Clindamycin

A

Binds 50s ribosome

  • 23s rRNA component
  • Prevents translocation
  • Same as macrolides
52
Q

Clindamycin Resistance

A

23s rRNA = component of 50s ribosome

  • Location of macrolide binding
  • methylation of this site causes resistance
  • same as macrolides
53
Q

Clindamycin

A

Covers some gram (+)
-Staph, viridans Strep, Strep pyogenes, S. pneumonia
Covers many anaerobes
-Clostridium perfringens
-Mouth anaerobes: Fusobacterium, Prevotella, Peptostreptococcus

54
Q

Main use of Clindamycin

A

Main use is to cover anaerobes “above the diaphragm”
-Aspiration pneumonia
-Lung abscesses
-Oral infections (mouth anaerobes)
Lots of resistance to Clindamycin in B. fragilis
-Anaerobic infections “below the diaphragm”
-Metronidazole

55
Q

Clindamycin Adverse Effects

A 
Classic cause of c. difficile infection
-Up to 10% of pts
-Pseudomembranous colitis
-C. difficile overgrowth
-Massive, watery diarrhea
Antibiotic-associated diarrhea
-Milder than c. diff infection
-Changes in GI flora
-Less absorption of solutes causes osmotic diarrhea
-Stops when drug discontinued
56
Q

Linezolid

A

Binds to 50s ribosome
Blocks initiation
Main use: Vancomycin resistant enterococcus (VRE)
-Epidemics in hospitals
-Usually occurs in patients with prior antibiotic treatment

57
Q

Linezolid S/E

A

Weak monoamine oxidase (MAO) inhibitor
Can cause serotonin syndrome
High risk when given SSRIs
Fever, confusion, agitation, hyperreflexia

58
Q

Streptogramins

A 
Quinupristin/Dalfopristin
-Block protein synthesis 50s ribosome
-Used together for sequential protein synthesis block
-Synercid (quinupristin/dalfopristin)
Used for Vancomycin resistant bacteria
-VRSA
-VRE
59
Q

Which protein synthesis inhibitor is not bacteriostatic?

A

Aminoglycosides: Bacteriocidal

-Misread proteins travel to cell membrane and increase permeability

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