antibiotics

Question 1

action of penicillin

Answer 1

1. penicillin (or other cell wall synthesis inhibitor) added to bacterial growth
2. cell grows but can’t synthesise new cell wall to accommodate
3. growth continues and cytoplasm (covered in plasma membrane) squeezes out
4. cell can’t “pinch-off” cytoplasm because a division furrow needs ability for cell wall
5. cell wall shed = spheroblast
   - - vulnerable to lysis

Question 2

penicillins are what type of antibiotic?

Answer 2

bactericidal antibiotics

Question 3

tetracyclines and sulphonamides are…

Answer 3

bacteriostatic antibiotics

Question 4

accidental discovery of _________ by Sir Alexander Fleming in ______. A fungal spore drifted into Fleming’s laboratory from allergist John Freeman’s laboratory. Fleming was unable to purify the mold juice for medical use. Lord Florey and Ernst Chain revealed the potential of _______ as a ___________ agent.

Answer 4

accidental discovery of penicillin by Sir Alexander Fleming in 1928. A fungal spore drifted into Fleming’s laboratory from allergist John Freeman’s laboratory. Fleming was unable to purify the mold juice for medical use. Lord Florey and Ernst Chain revealed the potential of Penicillin as a chemotherapuetic agent.

Question 5

Florey’s breakthrough result

Answer 5

1. established dose of bacteria to kill a mouse with a peritoneal injection of bacterial suspension 1 day prior to penicillin treatment
2. 8 hour injections of “penicillin”
   - for 36 hours some mice sick/died
   - as time progressed, health improved
   - 36-40 hours infected mice were indistinguishable to healthy mice
   - at 10 days 21/24 mice had survived

Question 6

5 targets for antibiotics

Answer 6

1. inhibition of cell wall synthesis - e.g. penicillin - transpeptidases/PBPs and transglycolyases
2. inhibition of protein synthesis - e.g. aminoglycosides - bind to bacterial ribosomal RNA, disrupt structure - misfolded proteins - death. OR - incorporation of misfolded protein in to membrane - increased drug uptake
3. inhibition of DNA or RNA synthesis - e.g. Rifampicin, which binds to RNA polymerase
4. inhibition of folate synthesis - bacteriostatic
5. membrane disruption - e.g. daptomycin - lipopeptide antibiotic

Question 7

which enzyme does penicillin bind

Answer 7

DD-transpeptidase