Antibiotics Flashcards
What occurs when an aminoglycoside and a beta-lactam is mixed
they will both be inactivated - this does not occur in vivo
What are the ribosomal subunits for bacterial ribosomes?
30s and 50s –>70s, not bound to endoplasmic reticulum
What are the ribosomal subunits for eukaryotic ribosomes?
40s and 60s –> 80s, they are 50% larger than bacterial and are bound to the endoplasmic reticulum
By which two mechanisms do inhibitors of bacterial protein synthesis enter gram NEGATIVE bacterial cells?
Passive diffusion through the outer cell membrane channels (porin proteins) and energy dependent active transport system
Selectivity of bacterial protein synthesis inhibitors against bacterial cells is attributed to
Lack of 70s ribosomes in mammalian cells and lack of bacterial active transport systems in mammalian cells.
What is special about Amikacin of all the aminoglycosides?
it is the least susceptible to enzymatic inactivation; so generally reserved for treatment of serious infections caused by gram-negative bacteria that are suspected to be resistant to the other aminoglycosides
Tetracyclines inhibit mammalian protein synthesis - this leads to what effect?
antianabolic - increase in BUN levels
Tetracyclines absorb light in the visible region, leading to free radical generation - this is especially true for those with
a C-7 chlorine substituent - this can lead to severe phototoxicity. Demeclocycline is the most phototoxic
It is contraindicated to co-administer tetracyclines with what?
antacids, iron supplements, calcium, dairy or anything else with polyvalent metal ions
Tetracyclines have a high affinity for
calcified tissues - they chelate calcium
Tetracyclines have the possibility for what side effect, depending upon dose and duration of therapy?
teeth discoloration
Which glycylcycline is structurally related to the tetracyclines?
tigecycline (tygacil) - broad spectrum for IV infusion and is bacteriostatic at the clinical dose
Why is tigecycline not affected by mechanisms of resistance to tetracyclines, even though it is structurally related?
though its structure is related, it has a unique binding site on the 30s ribosomal subunit - it can be used in place of a tetracycline for infections with strains that are resistant to them
Tigecycline is not recommended for patients under 18, but definitely SHOULD NOT be administered to patients under 13. Why?
Tigecycline can cause permanent discoloration of teeth and bones
Which macrolide is contraindicated during pregnancy?
clarithromycin
