Antibiotics

Question 1

Antimicrobial

Answer 1

Interferes with growth and reproduction of a microbe

Question 2

Antibiotic

Answer 2

type of antimicrobial used as a medicine for animals

Question 3

Bactericidal

Answer 3

Kills bacteria

Question 4

Bacteriostatic

Answer 4

Halts bacterial growth

Question 5

Aims of an antibiotic

Answer 5

Selective toxicity, must have molecular target either not present in host, or structure different from host. Or different way to access target.

Question 6

Possible antibiotic mechanisms

Answer 6

Inhibit cell wall synthesis, inhibit membrane function, inhibit protein synthesis, inhibit nucleic acid synthesis.

Question 7

Beta lactams - penicillin

Answer 7

Inhibit cell wall synthesis. For example penicillin targets the penicillin binding proteins, inhibit the final cross-linking step in synthesis of peptidoglycan. Beta lactams have four ring structure, bind to prevent transpeptidation in population of replicating bacteria. Different members of family have different susceptibility to bacterial resistance mechanisms.

Question 8

Beta lactamases

Answer 8

Inactivate beta lactam antibiotics, and rapidly spread resistance mechanism. But can be blocked by addition of bulky side chains such as large aromatic rings, or by giving beta lactamase inhibitors.

Question 9

Other beta lactams

Answer 9

Cephalosporins and carbapenems. Diffrerent structure. Carbapenems often drugs of last resort as has excellent bactericidal activity against gram - and + anaerobic bacteria

Question 10

Vancomycin

Answer 10

Also targets cell wall synthesis, but binds at peptidoglycan cross links. Targets Gram positive bacteria.
If bacteria use D-lactate instead of alanine to cross link then this confers resistance.

Question 11

Aminoglycosides

Answer 11

Bind to the 30s ribosomal subunit so inhibits the initiation complex and causes misreading of mRNA. Hence membrane is damaged and bacteria will die. Particularly useful against Gram negative rods.

Question 12

Tetracyclines

Answer 12

Bind to the 30s ribosomal subunit and block the tRNA from entering the acceptor site. Selectivity for bacterial cells is dependent on uptake (not into human). As in vitro application will also block tRNA in human cells.

Question 13

Chloramphenicol

Answer 13

Acts on the 50s subunit to block the action of peptidyltransferase, such that new peptide bonds cannot be synthesised. Does also inhibit protein synthesis in mitochondria of human cells, but apparently limited impact there/

Question 14

Macrolides

Answer 14

Bind to the 50s ribosomal subunit and block translocation. SO tRNA is not released and donor site remains occupied so protein synthesis halts. Azithromycin, erythromcin are in clinical use.