Antibiotics

garytse86

Hello. I am doing an investigation on antibiotics. Does anyone know what the exact mechanism of action does methicillin follow? I tried to look for this on google but unfortunately all I can find is MRSA..... I think Methicillin has same mode of action as Penicillin G (interfering with cell wall synthesis), but I am not sure.

And what about Novobiocin?

Any help will be appreciated.

Gary.

iansmith

Methicillin is a antistaphylococcal penicillins and it is beta-lactamase-resistant. You are right to think that the mode of action is similar to Pen G.

Novibiocin inhibits DNA synthesis by binding the beta-subunit of DNA gyrase
http://www.harcourt-international.co...ks/pdf/360.pdf

This is some old litterature about Novobiocin and its mode of action.
http://www.pubmedcentral.nih.gov/art...i?artid=314970

garytse86

Thank you very much, actually I found the first pdf file just a few hours ago.

The second site is very helpful actually! Thanks!

garytse86

I know that most bacteria have an active transport mechanism for uptaking tetracycline, but is there any other mechanism that does the same for other antibiotics that interfere with protein synthesis? (e.g. Chloramphenicol, Erythromycin, Tetracycline and Streptomycin).

Why do Gram positive bacteria accumulate more erythromycin (100 times) than Gram negative bacteria? (http://www.elmhurst.edu/~chm/vchembo...ntibiotic.html).

What about Chloramphenicol, Tetracycline and Streptomycin (or any other antibiotics that interfere with protein synthesis)? Do Gram positive bacteria accumulate these more than Gram negative species. If so, why?

Why is novobiocin more effective against Gram positive bacteria?


Thank you very very much in advance. I know this is a lot but unfortunately I cannot find answers to the questions above on the internet using google etc.

Gary

iansmith

This might be useful
http://www.pubmedcentral.nih.gov/art...i?artid=252138
http://www.pubmedcentral.nih.gov/art...i?artid=221988

Chloramphenicol and tetracycline are broad range antibiotic and there probably not difference between gram-negative and gram positive. For Spectinomycin, there might be a difference since it has more narrow range of action. It mostly effective against gram-positive and a few gram-negative but the difference in accumulation has not been documented, as far as i know.

For novobiocin, it might be related to the permeability of the membrane in gram-positive and the presence of certain transport proteins that are mostly absent in gram-negative. Also for gram-negative, a 2 transport systems is required to internatilze large molecules, one to transport inside the periplasm and the other to transport from the periplasm into the cytoplasm. If either one is missing, the transport does not occurs. However, this is speculation.
http://aac.asm.org/cgi/content/full/43/6/1347