Protein synthesis Inhibitors - 30s Ribosome

Question 1

Aminoglycosides

Answer 1

• Gentamycin, neomycin (can cause anemia), amikacin, tobramycin (P. aeruginosa coverage), streptomycin
• Mech: Inhibits 30s Subunit
• Use: severe gram neg. aerobic bacteria
• Amikacin is broadest spectrum
• Gentamycin most commonly prescribed AG
• Neomycin topical only
• Synergy with lactams and vancomycin
• toxicity: nephrotoxic, ototoxic, teratogen
• ” ‘Mean (amine) GNATS can NOT kill anaerobes”

Question 2

Tetracylines

Answer 2

• Tetrac, Doxy, Tige, Mino
• Mech: inhibits 30s, prevents attachment of aminoacyl-tRNA
• Main use is ACNE VULGARIS
  Use: Vibrio, acne, chlamydia, Ureaplasma, Mycoplasma, Tularemia, H. Pylori, Borrelia, Rickettsia
• Hairy Tongue, Tooth discoloration and enamel weakness, C. Difficile overgrowth
• Disulfiram-like Reaction
• Don’t take with milk, antacids, or iron, don’t give if pregnant
• Tigecycline has activity against MRSA and VRE, MDR
• “VACUUM The BedRoom

Question 3

Macrolides

Answer 3

• Erythromycin, Azithromycin, Clarithromycin
• Inhibits peptide translocation by binding to 50s
  Use: URI; Pneumonia and STDs, 2nd line agent for skin/soft tissue (not MRSA), frequently used for URI
• Erythromycin used in patients allergic to penicillin
• Azithromycin preferred therapy for urethritis caused by chlamydia (Z-pack)
• Safest of Antimicrobials
• Metabolized by Cyp450

Question 4

Chloramphenicol

Answer 4

• Mech: inhibit 50s peptidyltransferase
• Use: meningitis (pen allergic pt.), Rickettsia in children, HFlu, Bacteroides
• mostly bacteriostatic for all bacteria except H. Flu (bactericidal)
• Toxicity: gray baby syndrome, anemias, teratogenic, inhibits CYP450
• Crosses BBB

Question 5

Clindamycin

Answer 5

• Mech: 50s subunit
• Use: non-enterococcal, gram pos. cocci, bone and joint infection, anaerobes above the diaphragm
• accumulates in patents with renal or liver failure
• C. Difficile infection

Question 6

Linezolid

Answer 6

• Mech: 50s, prevent formation
• Spec: strep cocci, entero, staph
• Clinical uses: VRE, MRSA, S. pneumo, complicated skin infections
• Toxicity: Bone marrow suppression, serotonin syndrome

Question 7

Quinuprostin/dalfopristin (streptogramins)

Answer 7

• Mech: binds 50s
• synergism
• slow IV infusion only
• Clinical use: reserved for serious infection by multi drug resistant Gram pos. organisms
• VRE, enterococcus, MRSA
• Toxicity: arthralgia and myalgia

Question 8

Mupirocin

Answer 8

• Mech: Reversibly inhibits isoleucyl transfer-RNA synthetase enzyme which inhibits protein transaction
• PK: applied topically
• Use: MRSA and S. progenies
• Toxicity: only apply in small areas