Purpose: Understand the classes of antibiotics, their functions, and target bacteria.
Mnemonic: "Antibiotics Can Protect The Queen's Men, Servants, and Guards"
Each letter stands for a class of antibiotics.
Classes of Antibiotics
1. Aminoglycosides (A)
Target: Gram-negative bacteria.
Examples: Streptomycin and Gentamicin.
Mechanism: Inhibit protein synthesis.
Ribosome Structure: Affected by 30s subunit inhibition (bacteria have 50s and 30s subunits vs. human 60s and 40s).
2. Cephalosporins (C)
Target: Both gram-negative and gram-positive bacteria.
Examples: Cefazolin and Cefadroxil.
Mechanism: Inhibit cell wall synthesis.
Cell Wall Structure: Breaks peptide links between sugar molecules.
3. Penicillins (P)
Initial Target: Gram-positive bacteria.
Examples: Penicillin G and Ampicillin.
Mechanism: Inhibit cell wall synthesis.
Resistance: Development of beta-lactamase enzymes by bacteria.
Evolution of Penicillins: Creation of smaller antibiotics like Ampicillin.
Methicillin: Effective against resistant bacteria but faces MRSA.
4. Tetracyclines (T)
Target: Gram-positive and gram-negative bacteria.
Examples: Tetracycline and Doxycycline.
Mechanism: Inhibit protein synthesis at the 30s subunit.
5. Quinolones and Fluoroquinolones (Q)
Target: Gram-positive and gram-negative bacteria.
Examples: Ciprofloxacin.
Mechanism: Inhibit DNA replication.
Process: Stops topoisomerase from unwinding DNA.
6. Macrolides (M)
Target: Gram-positive bacteria.
Examples: Erythromycin.
Mechanism: Inhibit protein synthesis at the 50s subunit.
7. Sulfonamides (S)
Target: Gram-positive and gram-negative bacteria.
Examples: Sulfamethoxazole.
Mechanism: Inhibit folate synthesis.
Folate Requirement: Bacteria synthesize their own, humans do not (dietary need).
8. Glycopeptides (G)
Target: Gram-positive bacteria.
Examples: Vancomycin.
Mechanism: Inhibit cell wall synthesis.
Conclusion
A variety of antibiotics target different processes in bacterial cells such as protein synthesis, cell wall synthesis, DNA replication, and folate synthesis.
Bacterial resistance is a significant challenge, necessitating the development of new antibiotics and strategies.