1.5 Antibiotics

Question 1

Classify antibiotics by mode of action x 3

Answer 1

1. Inhibition of nucleic acid synthesis
2. Modification of cell wall integrity + synthesis
3. Inhibition on protein synthesis

Question 2

1. Inhibition of nucleic acid synthesis x5

Answer 2

1. Sulphonamides
2. Trimethoprim
3. Quinolones
4. Nitroimidazoles
5. Rifampicin

Question 3

2. Modification of Cell wall integrity + synthesis

how work

x4

Answer 3

Contain B lactam ring
mimics D alanyl D alanine peptide chains in walls

Act group of bactericidal abx triggering cell lysis

1. Penicillin
2. Cephalosporin
3. Carbapenem
4. Vancomycin

Question 4

3. Inhibition of protein synthesis

Answer 4

Act on bacterial ribosome to prevent reproduction and growth

50s bacterial (humans 60/40)

1. Chloramphenicol
2. Macrolides

Linezolid

30

3. Tetracyclines
4. Aminoglycosides

Question 5

Sulphonamides

Answer 5

Nucleic Acid

Inhibit formation of dihydropteroic acid

Question 6

Trimethoprim

Answer 6

Nucleic Acid

Inhibits dihydrofolate reductase
high affinity with bacterial subset allow selective toxicity

Question 7

Quinolones

Answer 7

Nucleic acid

cipro

Inhibit DNA gyrase
prevent formation of coiled DNA

Question 8

Nitroimidazoles

Answer 8

Metronidazole

Nucleic acid

Nitrogoup interferes with DNA production and coiling intracellularly

especially anaerobic and protozoal

Question 9

Rifampicin

Answer 9

Nucleic acid

Prevents conversion DNA into RNA
inhibit RNA polymerase enzymes

Question 10

Penicillin

Answer 10

Eg BenPen
first group isolated

followed ‘Pen V’ PO active

Resistance to B lactamase improve penetration v some organisms

Fluclox

Question 11

Cephalosporin

Answer 11

Similar MOA group by generation

Act group of bactericidal abx triggering cell lysis

Question 12

Carbapenem

Answer 12

Eg Mero

Act group of bactericidal abx triggering cell lysis

Highly resistant penicillinase

Question 13

Vancomycin

Answer 13

Act group of bactericidal abx triggering cell lysis

inhibit peptidoglycan formation in cell wall

Question 14

Chloramphenicol

Answer 14

inhibits 50s subunit transpeptidation

Question 15

Macrolides

Answer 15

erythromycin

prevent translocation

Question 16

Tetracyclines

Answer 16

block binding tRNA in 30s subunit

Question 17

Aminoglycosides

Answer 17

gentamycin

block binding within 30s subunit cause miscoding of mRNA chain

Question 18

Antibiotic prophylaxis

why / what for

aim

what procedures

Answer 18

Prior procedure
- result in bacteraemia
plasma levels therapeutic when exposure to micro organism occurs

smaller systemic effects of bacterameia
reduce possibility of infection

aims to reduce effect skin flor inoculated into circ
- guided by site

Commonly used in procedures with implantation of foreign materials
ortho/ general

Question 19

Principle of prophylaxis

Answer 19

Timing coincide w/ bacterial inoculation
usually administered at induction

optimum timing aprox 30m before kts

too early - peak conc will fall - reduce penetration

too late similar effect

Tourniquet - consideration given prior to inflation

prolong admin no benefit

Question 20

Advantages prophylaxis

Answer 20

reduced wound infection

improved tissue healing

shorter postop recovery

Question 21

Disadvantages prohlyaxis

Answer 21

allergic rxn - mild - life threat

repeat exposure increase MDR

Removal of protective colonizers (cephalo) c diff

Aminoglycoside - interfere drug metabolism

Poor evidence in some surgery

Timing for max benefit

BSA not tailored