-Elrich; antimicrobial agent must be more toxic to pathogen than pathogen's host -Is possible because the difference in structure or metabolism between pathogen and its host
6 ways antimicrobial drugs affect pathogens
1.Inhibit cell wall synthesis
2.Inhibit protein synthesis
3.Disrupt cyotplasmic membrane
4.Inhibit metabloic pathways not used by humans
5.Inhibit nucleic acid synthesis
6. block pathogen's recognition of or attachment to host
How cell wall synthesis is inhibited by antimicrobials. Examples.
-prevent cross-linkage of NAM subunits in peptidoglycan (penicillin, cephalosporin)
-Interfere with alanine-alanine bridges that connect NAM in G+(vancomycin)
-Block transport of NAG and NAM from cytoplasm (bacitracin)
6 ways protein synthesis is inhibited by antimicrobials
1. Change shape of 30s so can't read mRNA (streptomycin)
2.Block tRNA docking site which prevents growing polypeptide (tetracycline)
3.Block enzymatic site at 50s, preventing peptide bond formation (chloramphenicol)
4.Bind to a different portion of the 50S, preventing translation(lincosamides)
5.Block ribosomes from attaching to mRNA, no effect on human (antisense nucleic acid)
6.Block initiation of translation,last resort (oxazolidinone)
How antimicrobials interfere with cytoplasmic membranes
-disrupt cm by forming a channel through it, damaging its integrity.
-Nystatin and Amphotericin attach to ergosterol, disrupting the membrane and causing lysis to the cell
How sulfanomindes disrupt synthesis of folic acid
act as analogs of PABA and compete for the active site for the enzyme involved in prod. of dihyrdofolic acid. Competition leads to decrease in production of THF, DNA, RNA. leads to cessation of metabolism and cell death.