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Protein synthesis inhibitors Flashcards

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1
Q

Antibacterial Agents that Inhibit Protein Synthesis by interaction with bacterial ribosomes

A

Aminoglycosides
Tetracyclines
Chloramphenicol

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2
Q

Antibacterial Agent that Inhibit Protein Synthesis by blocking initiation

A

Oxazolidinones (linezolid)

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3
Q

Antibacterial Agents that Inhibit Protein Synthesis by inhibiting tRNA synthesis

A

Mupirocin

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4
Q

Antibacterial Agent that Inhibit Protein Synthesis by disruption of RNA processing

A

Aminoglycosides

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5
Q

Drug that blocks binding of aminoacyl moiety of charged tRNA molecule to acceptor site of complex

A

Chloramphenicol, ketolides (Direct Binding to 50S Subunit)

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6
Q

Drug prevents translocation of peptidyl tRNA from acceptor site to donor site on the 50S ribosomal subunit

A

Macrolides, clindamycin, streptogramins( Direct Binding to 50S Subunit)

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7
Q

Drug that blocks binding of amino acid charged tRNA to acceptor site of ribosome mRNA complex

A

tetracyclines (Direct Binding to 30 S Subunit)

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8
Q

Drugs that can block formation of initiation complex between ribosomes and mRNA, misread mRNA, block translocation of mRNA

A

aminoglycosides (Direct Binding to 30 S Subunit)

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9
Q

“-static” drugs may be “-cidal” depending on:

A

Drug concentration
Site of infection
Infecting organism
ie., linezolid is “–static” for enterococci and staph, but “-cidal” for strep

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10
Q

aminoglycosides: 2 effects on bacterial cell resulting in death:

A

Bind negative charges in outer phospholipid membrane, displacing cations that link phospholipids together  disruption of wall and leakage of contents
Irreversibly disrupt protein synthesis by blocking initiation, misreading mRNA, blocking translocation

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11
Q

3 known mechanisms of aminoglycoside resistance:

A

1) Modification of aminoglycoside molecule by enzymes can’t bind ribosome: Plasmids,
Amikacin has side chain that protects against deactivation by enzymes (beats this kind of resistance)
2) Binding of aminoglycosides on rRNA altered
3) Reduced uptake of aminoglycosides: mutations

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12
Q

How do you combat aminoglycoside resistance?

A

use agents that target cell wall in conjunction with aminoglycosides

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13
Q

What bacteria are aminoglycosides active against?

A

aerobic gram-negative bacilli
Klebsiella species, Enterobacter, Pseudomonas aeruginosa
little activity against anaerobes and gram-positive organisms

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14
Q

What infections are aminoglycosides used to treat?

A

UTI, respiratory tract, skin and soft-tissue infections

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15
Q

List aminoglycosides

A

streptomycin
gentamicin, tobramycin, amikacin
neomycin, kanamycin
spectinomycin

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16
Q

Streptomycin

A

Aminoglycoside. Useful in treating enterococcal infections

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17
Q

Gentamicin, tobramycin, amikacin

A

Most widely used aminoglycosides. Cross-resistance between these drugs

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18
Q

neomycin, kanamycin

A

aminoglycosides. limited to oral or topical due to toxicity. (nephrotoxic)

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19
Q

Spectinomycin

A

structurally related to aminoglycosides but lacks amino sugars and glycosidic bonds. Used as tx for gonorrhea in PCN allergic pts.

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20
Q

Adverse effects of aminoglycosides

A

1) Otoxicity = may be irreversible. Genetic predisposition. Cochlear toxicity=high pitched tinnitus, progressing to high pitch deafness
Vestibular toxicity=HA, N, V, vertigo
Streptomycin most ototoxic; not reported with gentamicin
2) Nephrotoxicity = usually reversible. Elevated serum creatinine, diminished concentration of urine
3) Neuromuscular blockade- aggravates muscle weakness in Parkinson’s or Myesthenia Gravis patients

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21
Q

Which aminoglycoside do you want to avoid if you have sulfite allergies?

A

Streptomycin ONLY (because it contains metabisulfite)

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22
Q

Which aminoglycoside causes bronchospasms and hoarseness after administered via nebulizer?

A

Tobramycin

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23
Q

Which amino glycoside affects digoxin metabolism by altering the GI flora responsible for its metabolism?

A

Neomycin

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24
Q

Which aminoglycosides are “Category D” and why?

A

Amikacin, streptomycin, tobramycin, kanamycin

8th cranial nerve toxicity seen in fetus when these antibiotics are administered.

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25
Which aminoglycosides are "Category C"?
Gentamicin, neomycin
26
What are the 3 most commonly used Tetracyclines?
Semisynthetics: Tetracycline Doxycycline Minocycline
27
Which bacteria to tetracycline work against?
Very broad spectrum!! Gram positive, gram negative, aerobic and anaerobes Mycoplasma pneumoniae Chlamydia Pneumoniae Trachomatis:Cervicitis, urethritis, PID, prostatitis (<35 yo), partners Rickettsia = RMSF (spirochetes) Borrelia burgdorferi = Lyme’s disease (spirochetes)
28
Short acting tetracyclines
Oxytetracycline, tetracycline | Frequent dosing needed
29
Intermediate-acting tetracyclines
Demeclocycline no longer used as antibiotic | Tx of SIADH (symptom of inappropriate ADH)
30
*Long-acting tetracyclines
Doxycycline and minocycline | BID dosing
31
How do tetracyclines work?
Inhibit protein synthesis by reversibly binding to the 30S subunit of RNA Blocks the addition of amino acids to newly forming peptides bacteriostatic (need the immune system's help)
32
What are the ADRs of tetracyclines?
Gastrointestinal: N, V, D = most common; Modified GI flora= candidiasis, C. diff Bony structures and teeth: Binds to newly formed/forming bones and teeth. Children < 8 yo (US); < 13 yo (Canada). Fetus (Category D) and breast fed infants can be affected Photosensitization Vestibular reactions-dizziness, vertigo (minocycline) Pseudotumor cerebri (idiosynchratic rxn) Lupus-like rxn with minocycline (reversible)
33
What is unique about tetracycline absorption?
``` Incompletely absorbed from the GI Further Impaired by concurrent ingestion: Dairy products Aluminum hydroxide Ca++, Mg++, iron or zinc salts Bismuth subsalicylate ```
34
What is unique about doxycycline elimination?
Elimination is mostly hepatic (whereas all other tetracyclines are predominantly kidney-elimination)
35
Third Generation TCN
Tigecycline (Tygacil)- Broad spectrum antimicrobial activity, including MRSA Indicated for treatment of complicated intra-abdominal infections and complicated skin and skin structure infections in adults Developed to overcome bacterial resistance mechanisms to TCNs (efflux and ribosomal mutations)
36
What are the indications for Chloramphenicol?
Gram (+), Gram (-) Because of blood dyscrasias it is reserved for life-threatening infections such as typhoid fever, RMSF, and meningitis in patients allergic to PCN.
37
Is chloarmphenicol bacteriostatic or bactericidal?
Both bactericidal and bacteriostatic depending on the bacteria species.
38
Neonates can't metabolize which antibiotic due to "gray baby syndrome?"
Neonates cannot metabolize Chloramphenicol and “gray baby syndrome” ensues. Gray baby syndrome consists of pallor, abdominal distension, vomiting and collapse. Accumulation can lead to death.
39
Macrolides
1) Erythromycin 2) Clarithromycin (Biaxin) 3) Azithromycin (Zithromax—Z-pak) (2 and 3: Semisynthetic derivatives: Derived from erythromycin; more acid stable, better tissue penetration and broader spectrum)
40
How do macrolides work?
Inhibit protein synthesis by binding to 50S ribosomal unit, blocking translocation and preventing peptide elongation Bacteriostatic; at high concentrations or with rapid bacterial growth= bactericidal
41
erythromycin is effective against which bacteria?
Erythromycin is effective against most Gram (+) bacteria and spirochetes. Specific bacteria include: legionella pneumophila, N gonorrhoeae, N. menigitidis, H. influenzae (only in combo with sulfonamide) Poor anaerobic coverage.
42
Clarithromycin is active against which bacteria?
Clarithromycin is active against gram (+) and anaerobic bacteria, H. influenzae, H. pylori, mycobacterium avium
43
Azithromycin is active against which bacteria?
Clarithromycin is active against gram (+) and anaerobic bacteria, H. influenzae, H. pylori, mycobacterium avium PLUS anaerobic coverage
44
Bacteria resistant to PCNs also resistant to which Macrolide?
Erythromycin
45
Adverse effects of Erythromycin
1) Gastrointestinal = most common-N,V,D and cramps-Binds to motilin receptor and increases peristalsis 2) Cholestatic jaundice-Most common with estolate salt form 3)CV (more common if administered IV parenterally) Ventricular arrhythmias-erythromycin Palpitations, chest pain, Dizziness, HA IV- QT prolongation
46
Clarithromycin (Biaxin)
Semisynthetic Macrolide. Spectrum of activity = to erythromycin + enhanced coverage of atypical mycobacteria Compared to erythromycin: Less GI upset and BID dosing N/D, abnormal taste, dyspepsia, HA, tooth discoloration, transient anxiety and behavioral changes
47
Azithromycin (Zithromax)
Semisynthetic Macrolide: Spectrum of activity < staph and strep coverage, > atypical mycobacterial and Haemophilus influenza coverage Great tissue penetration and prolonged intracellular half-life Angioedema(idiosyncratic rxn)
48
Which drugs inhibit CYP3A4?
Erythro, clarithromycin
49
Which drug is NOT metabolized by CYP3A4
Azithromycin
50
Ketolides
“New generation” of macrolide antibiotics Semi-synthetic derivative of erythromycin Higher binding affinity to 50S subunit (work a little better than macrolide) Displays greater potency against gram (+) organisms Displays activity against macrolide-resistant strains. Does not induce bacterial methylase (mechanism of resistance). Drug able to bind 50S subunit when site is methylated (mechanism of resistance)
51
Indications for Telithromycin (Ketek)
Tx of community-acquired pneumonia, sinusitis and bronchitis caused by S. pneumoniae, H. influenzae, Chlamydia pneumoniae, M. catarrhalis, Mycoplasma pneumoniae, S. aureus (but only use this if you have no other choice. "black box" warning. linked to liver failure/deaths)
52
Metabolism and elimination of Telithromycin (Ketek)
Hepatic metabolism with elimination in bile and urine
53
Spectrum of activity of Lincosamides: Clindamycin (Cleocin)
Gram positive = strep, staph, pneumococci Anaerobes = gram positive and negative Except clostridium difficile
54
Method of action of Lincosamides: Clindamycin (Cleocin)
Inhibits protein synthesis by binding to same receptor site as erythromycin (50S inhibitor)
55
Most important indication for Clindamycin (Cleocin) ?
the treatment of anaerobic or mixed (polymicrobial) infections Perforated viscus (with agent for GNR coverage) Mostly being replaced by metronidazole (Flagyl) Infections of female genital tract Inpatient PID, septic abortion, amnionitis Decubitis, venous stasis, or arterial insufficiency ulcers Aspiration pneumonia
56
1) What is the most common antibiotic to cause clostridium difficile toxin mediated diarrhea Pseudomembranous Colitis 2) What is the treatment of choice?
1) Clindamycin (Cleocin) | 2) Treatment of choice is metronidazole (Flagyl), (can also give Vanco PO orally)
57
Are Streptogramins: Quinupristin-Dalfopristin (Synercid) bacteriostatic or bactericidal?
Bacteriostatic
58
What are the indications for Streptogramins: Quinupristin-Dalfopristin (Synercid)?
life-threatening infections associated with vanco-resistant Enterococcus faecium (VRE) bacteremia tx of complicated skin/structure infections by methicillin-susceptible S. aureus or S. pyrogenes
59
Quinupristin-Dalfopristin (Synercid): Metabolism and ADRs
P450 3A4 inhibitor--(Nifedipine, cyclosporin drug interactions) IV only, limited tissue distribution, metabolized in liver to active metabolites ADRs: phlebitis, arthralgias, myalgias, hyperbilirubinemia
60
Indications for Oxazolidinones: Linezolid (Zyvox)
Indications: vanco-resistant Enterococcus faecium (VRE); nosocomial pneumonia due to S. aureus including MRSA or S. pneumoniae; complicated/uncomplicated skin/structure infections; gram (+) community acquired pneumonia
61
What is the MOA for Oxazolidinones: Linezolid (Zyvox)?
prevents function of initiation complex. Mechanism distinct from other 50S ribosomal inhibitors  active against bacteria that is resistant to other protein synthesis inhibitors
62
Is Linezolid bacteriostatic or bactericidal, and against which organisms?
BOTH!! Bacteriostatic against enterococci and staph; bactericidal against strept
63
ADRs of Linezolid
GI, HA thrombocytopenia Linezolid = MAOI= hypertension if used with adrenergic and serotonergic drugs
64
Which drug is a tRNA inhibitor?
Mupirocin (Bactroban)
65
How does Mupirocin (Bactroban) work?
Inhibits isoleucyl RNA synthetase | Inhibits protein synthesis due to loss of critical amino acid in peptide
66
What is Mupirocin (bactroban) active against?
Active against gram (+) cocci—expect to find on the skin so good topical ointment Used for topical treatment of skin ie., impetigo

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