Antibiotics

Question 1

Beta-lactams antibiotics

Answer 1

E.g. penicillin.
Have a bactericidal effect by inhibits the cell-wall synthesis. They target enzymes known as penicillin-binding proteins (PBPs), which are involved in the cross-linking of peptidoglycan chains in the bacterial cell wall. By binding to PBPs, beta-lactam antibiotics interfere with the transpeptidation reaction, preventing the formation of the cross-links essential for the structural integrity of the bacterial cell wall.
As a results, the bacteria is unable to maintain their cell wall integrity, leading to death.

Side-effects: well tolerated, but can cause allergic reactions.

Question 2

Beta-lactamases

Answer 2

An enzyme that can cleave the beta-lactam ring if it is not protected by any other group. This is a way for the bacteria to strike back. There is a group of penicillin’s that are not cleaved by beta-lactamase.

Beta-lactamases can be inhibited by anti-biotic beta-lactamase inhibitors, or the beta-lactam antibiotics can be designed with bulky side-chains, which also inhibits the beta-lactamase enzyme.

Question 3

Vancomycin

Answer 3

Inhibitor of the cell-wall synthesis, but with another mechanism of action from beta-lactams.
Vancomycin blocks the transpeptidation by gluing sterically to the D-Ala-D-Ala, recognizing the site, and binding there to block the transpeptidase and hinder the transpeptidase reaction.

Question 4

Aminoglycosides

Answer 4

Protein synthesis inhibitor. Act on ribosomes by irreversibly binding to them.

Question 5

Quinolones

Answer 5

Inhibitors of DNA synthesis.

Question 6

Ciprofloxacin (quinolones)

Answer 6

MOA: bactericidal + inhibition of bacterial topoisomerases and therefore the DNA unfolding process, severely affecting by preventing DNA synthesis.
Broad spectrum.

Adverse effects: a lot! Pseudomembranous colitis.
Liver failure.
Prolonged QT interval.
Bone marrow depression.
Seizures threshold lowered.
Photosensibilisation.

Question 7

Rifampicin

Answer 7

Inhibitors of RNA polymerase.
Bactericidal. Rifampicin binds the bacterial RNA polymerase and inhibits transcription.

Adverse effects: red coloring of urine, tears, and contact lenses. Liver affection, bone marrow depression, rash.

Question 8

Adverse effects of antibiotics

Answer 8

Toxic: Ototoxic, Nephrotoxic, Hematotoxic., Cardiotoxic (prolongation QT interval).

Allergy induction.

Change of normal composition of bacteria on skin and mucosa – colonization with resistant and/or pathogenic bacteria. Due to the use of broad-spectrum antibiotics.

Spreading of resistance strains (there are bacteria we do not want to treat). Iatrogenic infections with resistant strains at hospitals.