- Cell wall
- Protein synthesis (70S)
- DNA/RNA synthesis
- Other targets
a. Cytoplasmic phase
Fosfomycin– MurA analog, blocks muramyl-pentopeptide
b. Membrane associated phase
Bacitracin– blocks lipid carrier
c. Extra-cytoplasmic phase:
B-lactam (penicillin, cephalosporins, carbapanems, monobactams)- blocks transpeptidase ( penicillin binding protein), effects cross-linkage
Glycopeptide (vancomycin, avoparcin)- avoids transpeptidase formation, cause cross-linkage (D-ala D-ala termini)
Polymyxin (colistin)- effects peptidoglycan layer, increases permeability
2. PROTEIN SYNTHESIS
a. 50S (31 protein+ 23S RNA+ 5S RNA)
Macrolide, linozalid, streptogramin (MLS), chloramphenicol, clindamycin– Peptide bond formation.
B. 30S (21 protein + 16S RNA)
Tetracycline– blocks binding tRNA
Aminoglycoside– impair proofreading
Quinolone- a. DNA gyrase (topoisomerase II)- Beginning at the replication fork in gram negatives; GyrA* and GyrB / b.Topoisomerase IV- later at claving stage in gram positives; parC* and parE . (* where mutations usually occur)
Rifomycin– inhibits transcription (DNA –> mRNA)
Trimethoprim- It is a folic acid inhibitor. It binds to dihydrofolate reductase and inhibits the synthesis of tetrahydrofolic acid which plays an essential role in thymidine synthesis consequently inhibits DNA synthesis.
Sulfonamides- competitor for the enzyme dihydropteroate synthetas which blocks PABA joining folic acide molecule, so prevent folic acide synthesis which are essential for bacteria.
Note to myself: I will improve this section later.