Micro lecture 7

Question 1

True or False? Many antibiotics tend to bind more to the prokaryotic
ribosome (30S/50S) subunits than the eukaryotic ribosome (40S/60S).

Answer 1

True. – binding can be to 30S (small) or 50S (large)
ribosomal subunit (these are further subdivided)

Question 2

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.

Answer 2

• Aminoacyl-tRNA binding
• Peptide bond formation
• MRNA reading
• Translocation

Question 3

Aminoglycosides are made up of 2+ amino sugars and a _____________ (C6) ring.

Answer 3

Aminocyclitol (C6) ring.

Question 4

True or False? Aminoglycosides are usually aerobic G- rods and certain G+.

Answer 4

True.

Question 5

Aminoglycosides bind to __S ribosomal subunits.

Answer 5

30S.

Question 6

What is the general mechanism of action of Aminoglycosides and what is the end result?

Answer 6

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.)

Question 7

Name 4 examples of Aminoglycosides.

Answer 7

Gentamicin, tobramycin, amikacin & streptomycin.

Question 8

Gentamicin is often used alone against G- and with cell wall agent against (1) _____________. It is sometimes used against Staphylococcus, including (2) ____.

Answer 8

1. Streptococcus.

2. MRSA.

Question 9

True or false? Gentamicin is fairly toxic in the kidney and the ears.

Answer 9

True.

Question 10

Tobramycin & Amikacin are principally used against G+ bacteria.

True or False?

Answer 10

False, they are principally used against G- bacteria.

Question 11

Streptomycin is very toxic to the human body and is used only in certain situations. What are those situations?

Answer 11

Against drug-resistant Tuberculosis (TB) and plague (Yersinia pestis).

Question 12

What are Macrolides?

Answer 12

Chemicals that contain 12 to 22-carbon lactone rings linked to one or more sugars.

Question 13

Name 3 examples of Macrolides.

Answer 13

erythromycin, azithromycin and clarithromycin

Question 14

Is erythromycin bactericidal or bacteriostatic?

Answer 14

Bacteriostatic.

Question 15

What is the difference between bactericidal and bacteriostatic?

Answer 15

Bacteriostatic means capable of inhibiting the growth or reproduction of bacteria while bactericidal means capable of killing bacteria outright.

Question 16

Erythromycin binds to (1) __S rRNA of (2) __S ribosomal subunit
and inhibits peptide chain (3) __________

Answer 16

1. 23
   2 50
2. Elongation

Question 17

Erythromycin is often used in what type of allergy?

Answer 17

Penicillin allergy.

Question 18

True or False? Azithromycin and Clarithromycin are often less active than erythromycin.

Answer 18

False, Azithromycin and Clarithromycin are often MORE active than erythromycin.

Question 19

Tetracyclines are a _ ring structure with variety of side chains.

Answer 19

4

Question 20

Tetracyclines are moderately broad spectrum. Most are better at G+ than G-.

True or False?

Answer 20

True.

Question 21

Are Tetracyclines bactericidal or bacteriostatic?

Answer 21

Bacteriostatic

Question 22

Explain the general mechanism of action of Tetracyclines.

Answer 22

Tetracyclines combine with 30S ribosomal subunit. This inhibits the binding of aminoacyl-tRNA molecules to
the A site of the ribosome.

Question 23

Name 4 examples of Tetracyclines.

Answer 23

Tetracycline, doxycycline, minocycline, and tigecycline.

Question 24

List the conditions that tetracycline, doxycycline and minocycline are used to treat.

Answer 24

Treatment:

• Atypical organisms, inc pneumonias
• Chlamydia (chest & urogenital / STD)
• Lyme disease
• Acne

Question 25

What is doxycycline is used to treat?

Answer 25

Skin and chest G+ infections.

Note: Also used to treat malaria.

Question 26

Tigecycline is a new variant, moderate-spectrum.

True or False?

Answer 26

False. Tigecycline is a new variant, BROAD-spectrum.

Question 27

Chloramphenicol is an example of a protein synthesis inhibitor with a unique ____________ structure.

Answer 27

Nitrobenzene

Question 28

Is Chloramphenicol bactericidal and bacteriostatic?

Answer 28

Bacteriostatic.

Question 29

What is the general mechanism of action of Chloramphenicol?

Answer 29

Chloramphenicol binds to 23S rRNA on 50S ribosomal subunit and inhibits peptidyl transferase reaction.

Question 30

What is chloramphenicol used to treat?

Answer 30

Typhoid fever, brain abscesses, rickettsia and chlamydial

infections.

Question 31

True or False? Chloramphenicol is toxic with rare but serious side effect so conventionally only used in severe infections.

Answer 31

True.

Question 32

There are other examples of protein synthesis inhibitors. ___________ is an example of a protein synthesis inhibitor called Clindamycin.

Answer 32

Lincosamide.

Question 33

Lincosamide is principally used against G_ and anaerobes.

Answer 33

G-

Question 34

There are other examples of protein synthesis inhibitors. _____________ is an example of a protein synthesis inhibitor called linezolid.

Answer 34

Oxazolidinone.

Question 35

Explain the general mechanism of action of linezolid.

Answer 35

Linezolid binds to 50S & prevents formation of the 50S/30S ribosomal complex.