Pharmacology: Antibacterial Drugs

Antibacterial Drugs

• Patient tolerance, bacterial resistance, and physician preference influence the selection of a particular drug for a particular condition.
• Bactericidal drugs kill or destroy bacteria, while bacteriostatic drugs limit the growth and proliferation of bacteria.

Mechanisms of Antibacterial Drugs

• Inhibition of bacterial cell wall synthesis and function
• Inhibition of bacterial protein synthesis
• Inhibition of bacterial DNA/RNA function

Inhibition of Bacterial Cell Wall Synthesis and Function

• Penicillin and cephalosporins inhibit bacterial cell wall synthesis by inhibiting peptidoglycan production.
• Polymyxin antibiotics (polyfex, polymyxin B, colistin) disrupt the phospholipid bilayer, creating gaps in the bacterial cell membrane.

Bacterial Structure and Function

• Bacteria are unicellular microorganisms with a rigid cell wall, no true nuclear membrane, and basic subcellular organelles.
• They depend on a nourishing medium to provide metabolic substrates.

Pathogenic Effects of Bacteria

• Bacterial infections can be harmful to host organisms by competing for essential nutrients and releasing toxic substances.
• Certain bacteria inhibit the growth of other microorganisms and assist in digestion and nutrient synthesis.

Bacterial Nomenclature and Classification

• Bacteria are named according to their genus and species, with names in italic typeface.
• Examples include Escherichia coli and Streptococcus pyogenes.
• Classification is based on shape, histologic staining, and other characteristics.

Spectrum of Antibacterial Activity

• Broad-spectrum agents, such as tetracycline, are effective against many types of bacteria.
• Narrow-spectrum agents, such as isoniazid, are specific to a particular bacterium, such as Mycobacterium tuberculosis.

Inhibition of Bacterial DNA/RNA Synthesis and Function

• Fluoroquinolones (e.g., ciprofloxacin, levofloxacin) and sulfonamides inhibit bacterial nucleic acid synthesis by inhibiting folic acid production.
• Folic acid is essential for bacterial nucleic acid synthesis and amino acid production.

Resistance to Antibacterial Drugs

• Bacterial resistance can occur due to enzymatic destruction of the antibacterial drug, modification or masking of the drug's binding site, or reduced drug penetration into the bacterial cell.