rRNA inhibitors

Question 1

Oxazolidinones (Linezolid)

Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 1

Bacteriostatic/Cidal: Bacteriostatic
Spectrum:Drug resistanct Gram +, MRSA, VRE
Binds to:23 rRNA of 50S subunit
Mechanism: Prevents formation of initiation complex
Resistance: modifies 23 rRNA - no cross resistance with other drug classes
Adverse effects & toxicities: bone marrow suppression
Important Facts: Excellent bioavailability

Question 2

Aminoglycosides

(Gentamicin, Neomycin, Tobramycin, Streptomycin, Amikacin)
Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 2

(Gentamicin, Neomycin, Tobramycin, Streptomycin, Amikacin)
Bacteriostatic/Cidal: Bactericidal
Spectrum: Gram negative aerobes, and pseudomonas
Binds to: Act on 30S ribosome
Mechanism: Prevents formation of initiation comlex, Causes misreading of mRNA, early termination
Resistance: 3-S ribosome mutations, expression of ribosomal methyltransferases, enzymes that acetylate or phosphorylate the drug
Adverse effects & toxicities: Nephroxity, ototoxicity, teratogen(fetal developmental errors)
Important Facts: Inhibits initiation, elongation, termination. Small and excluded from CSF. Synergetic with penicillin, solely work on aerobic microbes

Question 3

Tetracyclines

(Tetracycline, Doxycycline, Minocycline)
Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 3

(Tetracycline, Doxycycline, Minocycline)
Bacteriostatic/Cidal: Bacteriostatic
Spectrum: Broad with some specific resistance
Binds to: 30s subunit
Mechanism: Prevents attachment of aminoacyl-tRNA
Resistance: Intrinsic - decreased uptake, increased efflux, alteration of ribosomal target
Adverse effects & toxicities: Forms chelates with metal ions which decrease gut absorption, inhibits child bone grwoth, pregnancy class D
Important Facts: Children and pregnant women should not take it.

Question 4

Chloramphenicol

(cholramphenico)
Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 4

Chloramphenicol

(cholramphenicol)
Bacteriostatic/Cidal: Bacteriostatic
Spectrum: Meningitis
Binds to: 50 S subunit
Mechanism: prevents peptide bond formation
Resistance: Plasmid -encoded acetyltransferase modifies drug, preventing its binding to the ribosome
Adverse effects & toxicities: Toxic - bone marrow depression and aplastic anemia. Gray baby syndrom - infants lack abilit to conver it to non-toxic
Important Facts: new borns and pregnant women should not take

Question 5

Macrolides

(Erythromycin, Azithromycin, Clarithromycin)
Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 5

(Erythromycin, Azithromycin, Clarithromycin)
Bacteriostatic/Cidal: Bacteriostatic
Spectrum: Broad coverag of respiratory, chlamydia
Binds to: 23S rRNA of 50S subunit
Mechanism: Inhibits translocation (movement of tRNA)
Resistance: methylation of 23S rRNA binding site, increased efflux. Hydrolysis of the macrolide
Adverse effects & toxicities: GI discomfort, hepatic failure, inhibit CyP450, QTc interval prolongation
Important Facts: should not be used in newborns and pregnant women

Question 6

Lincosamide

(Clindamycin)
Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 6

(Clindamycin)
Bacteriostatic/Cidal: Bacteriostatic
Spectrum: broad spectrum, anaerobic, acne
Binds to: 23S rRNA of 50S subunit
Mechanism: Blocks translocation
Resistance: Mutation of ribosome, methylation of rRNA, Cross -resistance with macrolides, and streptogramins, adenylation of drug
Adverse effects & toxicities: Hypersensitivity - Fever and rash
Important Facts:

Question 7

Streptogrogramins

(Quinupristin, Dalfopristin)
Bacteriostatic/Cidal
Spectrum
Binds to
Mechanism
Resistance
Adverse effects & toxicities
Important Facts

Answer 7

(Dalfopristin, quinupristin)
Bacteriostatic/Cidal: Bactericidal if combined
Spectrum: mulitple drug resistant Gram +
Binds to: 50s subunit
Mechanism: Block translocation
Resistance:rMthylase prevents binding to target enzymes inactivate the drugs, increased efflux, cross resistance with macrolides and clindamycine
Adverse effects & toxicities: HIgh incidence including arthralgia and myalgias. Inhibits CyP450
Important Facts