Microbio: Antibacterials

Penicillin and Cephalosporin

• Beta-lactams

• Inhibit transpeptidation which blocks NAG and NAM cross-linkage and makes the cell wall weak

• Beta-lactam ring mimics the shape of PBPs (penicillin binding proteins)

Vancomycin

• Not a beta-lactam but still a cell wall inhibitor

• Inhibits transpeptidation by binding to D-ala-D-ala

Bacitracin

• Interferes with bactoprenol, which is needed to anchor peptiodglycan

• Topical use only, human cells have similar enough lipids to cause an issue if ingested

Aminoglycosides and Tetracyclines:

• Protein synthesis inhibitors

• Disrupt peptide synthesis by binding 30S ribosomal subunit.

• Aminoglycosides also bind the 16S ribosomal rRNA in host mitochondira making them toxic.

• Bacteriostatic only.

Macrolides, Lincosamides, Chloramphenicol, and Oxazolidinones:

• Protein synthesis inhibitors

• Disrupt peptide synthesis by binding 50S ribosomal subunit.

• They are less toxic and more widely used.

• Lincosamides have limited use due to C. diff infection risk

• Chloramphenicol has limited use due to toxcity, affects microbiome

Fluoroquinolones

• DNA synthesis inhibitor

• Inhibit DNA gyrase

• Only used in severe infections because it is very toxic

Rifamycins

• RNA synthesis inhibitor

• Inhibit RNA polymerase

• Very toxic, always used in combination with another antibiotic

Sulfonomide, Trimethoprim

• Metabolic inhibitors

• Similar structure to enzymes which leads to blockage

• Block synthesis of folic acid

• Not toxic to humans because we get folic acid from diet

• Usually only bacteriostatic