Summary Antimicrobial Mechanisms

Antimicrobial Mechanisms
ILOs: the difference between gram positive and gram-negative, identify the targets, be able
to apply knowledge of chemistry to examples.
Areas that antimicrobials target:
 DNA via DNA gyrase inhibitors or nitroimidazole
 Protein synthesis via oxazolidinones, tetracyclines, macrolides, chloramphenicol and
erythromycin (think COMET)
 Metabolism via DHFR inhibitors and sulfa drugs.


Bacterial DNA




 Circular and large in length
 1300um
 Supercoiling=helix of a helix
 Superhelix formed.
 Usually negative supercoiling: compact and loosen the strands of DNA to make it
easier to replicate.
 Positive supercoiling: less loose so protection from denaturing and extreme hot
conditions. Found in thermophilic bacteria.
DNA gyrase




 Found in gram-negative bacteria.
 Topoisomerase IV in gram-positive.
 Achieves supercoiling.
 It cuts a section of DNA, threads it through and reseals the break.
 Uses ATP to drive it.

DNA gyrase inhibitors
First-generation quinolone:
 nalidixic acid
 gram -ve