Anti-Bacterial Drugs

Question 1

To achieve selective toxicity a drug must…

Answer 1

Kill or inhibit growth of target organism, without intolerable damage to host cells.

Question 2

By what mechanisms can this be achieved?

Answer 2

Affecting (1) affect DNA synthesis and repair, (2) Prevent Cell Division (3) Affect protein synthesis, (4) Affect plasma membranes or (5) Effect cell wall of bacteria.

Question 3

By what mechanism do Sulphonamides and Trimethoprim (Dihydrofolate reducate inhibitor) act on bacteria?

Answer 3

Sulphonamides stop the bacterial folate conversion, thus inhibiting nucleic acid synthesis. Both are Static, not cidal.

Question 4

By what mechanism do Quinolones and Fluoroquinolones act?

Answer 4

Inhibit supercoiling of bacterial DNA.

Question 5

Spectrum of Activity for Quinolones and Fluoroquinolones

Answer 5

Early Quinolones have a narrow spectrum (G-ve only), Fluoroquinolones have a wider spectrum. All generally poor vs. obligate anaerobes. Both are cidal.

Question 6

By what mechanism do Doxorubicin and Nitroimidazoles act?

Answer 6

Bind to DNA template and prevent transcription, duplication or cause damage.

Question 7

Spectrum of Activity Nitroimadazoles

Answer 7

Only effective againsts obligate anaerobes. It is cidal.

Question 8

What drugs can be used to prevent bacterial cell division? (3)

Answer 8

Vincristine (anti-cancer), Griseofulvin (anti-fungal), Benzimadoles (anti-parasitic)

Question 9

By what mechanism do Chloramphenicol, Tetracyclines, Aminoglycosides, Macrolides and Lincosamides act?

Answer 9

All inhibit protein synthesis.

Question 10

Spectrum of activity - Chloramphenicol

Answer 10

Broad Spectrum (static)

Question 11

Spectrum of activity - Tetracyclines

Answer 11

Broad Spectrum (static)

Question 12

Spectrum of activity - Aminoglycosides

Answer 12

Mainly G-ve. No activity against obligate anaerobes. (cidal)

Question 13

Spectrum of activity - Macrolides and Lincosamides

Answer 13

Narrow spectrum (G+ve mainly). Good against obligate anaerobes, and other special species e.g. Mycobacterium.

Question 14

By what mechanism do Pencillins and Cephalosporins act?

Answer 14

Cell Wall Active Agents (Beta-Lactams) - all are cidal. All affect the bacterial cell wall, inhibiting cross linking of polymers.

Question 15

Spectrum of Activity - Natural Pencillins

Answer 15

Narrow spectrum, G+ve. Sensitive to Beta-Lactamase. Example: Pencillin G.

Question 16

Spectrum of Activity - Anti-Staphylococcal Penicillins

Answer 16

Narrow spectrum. Resistant to beta-lactamase produced by Staphs. Example: Cloxacillin.

Question 17

Spectrum of Activity - Aminopenicillins

Answer 17

Broad spectrum, succeptible to Beta-lactamase produced by Staphs. Example: Amoxycillin

Question 18

Spectrum of Activity - Extended Spectrum Penicillins

Answer 18

Broad spectrum, includes difficult G-ve. Example: Ticarcillin.

Question 19

Why were Cephalosporins developed?

Answer 19

To improve Penicillin spectrum. First ones developed similar to Aminopenicillins but were not susceptible to Staph B-L.

Question 20

What is the veterinary Cephalosporin used?

Answer 20

Cephalexin