ANTIMICROBIAL DRUGS

Mechanisms of antimicrobial drug action:

1. Inhibition of cell wall synthesis
2. Cell membrane function inhibitors
3. Inhibition of protein synthesis
4. Inhibition of nucleic acid synthesis
5. Antimetabolites

Mechanisms of resistance to antibiotics

1. Production of enzymes that inactivate the drug (eg. b -lactamase, which inactivates beta lactam antibiotics; acetyl transferases, which inactivate chloramphenicol; kinases and other enzymes, which inactivate aminoglycosides.
2. Alteration of the drug-binding site: this occurs with penicillins, aminoglycosides and erythromycin.
3. Reduction of drug uptake by the bacterium: eg. Tetracyclines
4. Alteration of enzymes: eg. Dihydrofolate reductase becomes insensitive to trimethoprim.