Micro lecture 7 Flashcards
True or False? Many antibiotics tend to bind more to the prokaryotic
ribosome (30S/50S) subunits than the eukaryotic ribosome (40S/60S).
True. – binding can be to 30S (small) or 50S (large) ribosomal subunit (these are further subdivided)
Other than the inhibition of the prokaryotic ribosome (30S & 50S) and the inhibition of the eukaryotic ribosome (40S & 60S), what other steps in synthesis can antibiotics inhibit. Name 4 steps.
- Aminoacyl-tRNA binding
- Peptide bond formation
- MRNA reading
- Translocation
Aminoglycosides are made up of 2+ amino sugars and a _____________ (C6) ring.
Aminocyclitol (C6) ring.
True or False? Aminoglycosides are usually aerobic G- rods and certain G+.
True.
Aminoglycosides bind to __S ribosomal subunits.
30S.
What is the general mechanism of action of Aminoglycosides and what is the end result?
Aminoglycosides interfere with protein synthesis by directly inhibiting the 30S ribosomal subunit which leads to misreading of the messenger RNA – “false” proteins
produced. (A protein with many amino acid substitutions in it.)
Name 4 examples of Aminoglycosides.
Gentamicin, tobramycin, amikacin & streptomycin.
Gentamicin is often used alone against G- and with cell wall agent against (1) _____________. It is sometimes used against Staphylococcus, including (2) ____.
- Streptococcus.
2. MRSA.
True or false? Gentamicin is fairly toxic in the kidney and the ears.
True.
Tobramycin & Amikacin are principally used against G+ bacteria.
True or False?
False, they are principally used against G- bacteria.
Streptomycin is very toxic to the human body and is used only in certain situations. What are those situations?
Against drug-resistant Tuberculosis (TB) and plague (Yersinia pestis).
What are Macrolides?
Chemicals that contain 12 to 22-carbon lactone rings linked to one or more sugars.
Name 3 examples of Macrolides.
erythromycin, azithromycin and clarithromycin
Is erythromycin bactericidal or bacteriostatic?
Bacteriostatic.
What is the difference between bactericidal and bacteriostatic?
Bacteriostatic means capable of inhibiting the growth or reproduction of bacteria while bactericidal means capable of killing bacteria outright.
Erythromycin binds to (1) __S rRNA of (2) __S ribosomal subunit
and inhibits peptide chain (3) __________
- 23
2 50 - Elongation
Erythromycin is often used in what type of allergy?
Penicillin allergy.
True or False? Azithromycin and Clarithromycin are often less active than erythromycin.
False, Azithromycin and Clarithromycin are often MORE active than erythromycin.
Tetracyclines are a _ ring structure with variety of side chains.
4
Tetracyclines are moderately broad spectrum. Most are better at G+ than G-.
True or False?
True.
Are Tetracyclines bactericidal or bacteriostatic?
Bacteriostatic
Explain the general mechanism of action of Tetracyclines.
Tetracyclines combine with 30S ribosomal subunit. This inhibits the binding of aminoacyl-tRNA molecules to
the A site of the ribosome.
Name 4 examples of Tetracyclines.
Tetracycline, doxycycline, minocycline, and tigecycline.
List the conditions that tetracycline, doxycycline and minocycline are used to treat.
Treatment:
- Atypical organisms, inc pneumonias
- Chlamydia (chest & urogenital / STD)
- Lyme disease
- Acne
What is doxycycline is used to treat?
Skin and chest G+ infections.
Note: Also used to treat malaria.
Tigecycline is a new variant, moderate-spectrum.
True or False?
False. Tigecycline is a new variant, BROAD-spectrum.
Chloramphenicol is an example of a protein synthesis inhibitor with a unique ____________ structure.
Nitrobenzene
Is Chloramphenicol bactericidal and bacteriostatic?
Bacteriostatic.
What is the general mechanism of action of Chloramphenicol?
Chloramphenicol binds to 23S rRNA on 50S ribosomal subunit and inhibits peptidyl transferase reaction.
What is chloramphenicol used to treat?
Typhoid fever, brain abscesses, rickettsia and chlamydial
infections.
True or False? Chloramphenicol is toxic with rare but serious side effect so conventionally only used in severe infections.
True.
There are other examples of protein synthesis inhibitors. ___________ is an example of a protein synthesis inhibitor called Clindamycin.
Lincosamide.
Lincosamide is principally used against G_ and anaerobes.
G-
There are other examples of protein synthesis inhibitors. _____________ is an example of a protein synthesis inhibitor called linezolid.
Oxazolidinone.
Explain the general mechanism of action of linezolid.
Linezolid binds to 50S & prevents formation of the 50S/30S ribosomal complex.
