Bact protein synthesis inhibitor Flashcards
Name 2 key targets of antimicrobials that work by inhibiting bacterial protein synthesis?
50S, 30S bacteria ribosomal subunits
Name at least 2 classes of antibiotics which are 30S protein synthesis inhibitors
tetracyclines, glycylcycline, aminoglycosides
Name 3 examples of tetracyclines
tetracycline, doxycycline, minocycline
Tetracycline prevents binding of ___________ to the A site of mRNA-ribosome complex
–> preventing protein synthesis
tRNA
Tetracyclines should not be administered with dairy products or substances that contain divalent and trivalent cations (antacids) as this would lead to the formation of ___________, which would ___________ the absorption of the drugs.
non-absorbable chelates,
reduce
Comment on tetracycline’s antimicrobial coverage
broad spectrum activity against many
- Gram-negative
- Gram-positive bacteria
- atypical bacteria
- spirochetes
EXCEPT Pseudomonas & proteus
How are tetracyclines cleared?
Tetracycline- renal
Doxycycline & minocycline - hepatic (hepatic dysfn req dose adjustments)
Which drug is used in community acq penumonia (eg H influ, S pneumoniae) & MRSA?
Doxycycline
How are tetracyclines administered?
Usually oral
IV only on special requests
Can tetracyclines be used in pregnancy?
No,
cross placenta
concentrate in places w high calcium content- fetal bone & dentition
How is glycylcycline (tigecycline) administered?
IV (poor bioavailability)
Glycylcycline (tigecycline) was designed to overcome which two mechanisms of tetracycline resistance?
- Expression of efflux pumps
- Ribosomal protection (higher affinity to ribosome not easy to get dislodged by proteins)
Tigecycline is useful in targeting some of the resistant microbes including
- Methicillin resistant staphylococci (MRSA),
- Multidrug-resistant streptococci,
- Vancomycin-resistant enterococci (VRE),
- useful against carbapenem resistant strains of Extended-spectrum β-lactamase–producing gram-negative bacteria
What’s tigecycline not effective against?
pseudomonas + proteus (same as tetracycline)
How is tigecycline cleared?
Hepatic clearance– dose reduction for severe hep dysfn
Since tigecycline can treat resistant microbes, would it be a good option in bacteremia?
No, as tigecycline penetrates tissues well. Poor option for bloodstream infections.
Name at least 4 adverse effects associated with the use of tetracyclines & glycylcycline (tigecycline).
- Gastrointestinal distress (To reduce ulceration, drink plenty of fluids and do not take it before sleep)
- Phototoxicity (Like fluoroquinolones)
- Superinfection like thrush (fungal more common, CDAD only on prolonged use)
- Deposition in bone/primary dentition and may cause discoloration of teeth
The use of tetracycline and tigecycline is contraindicated in which populations of patients?
- Pregnant women,
- Breastfeeding women
- Children less than 7/8 years of age
What’s the difference b/n tetracycline VS aminoglycosides?
Tetracycline- bacteriostatic
Aminoglycosides- bacteriocidal (concentration dependent killing w PAE)
MOA of aminoglycosides
block formation of initiation complex, cause codon misreading, inhibit translocation
Aminoglycosides are transported across the inner membrane of Gram-negative bacteria by ___________ , which is an energy dependent process.
active transport
Aminoglycosides are particularly effective against _______ Gram-negative bacteria
aerobic
How is the action of aminoglycosides inhibited?
anaerobic conditions/ drop in pH
Name 5 examples aminoglycosides
gentamicin, streptomycin, tobramycin, amikacin, neomycin