Antibiotics: A Deeper Understanding of Their Actions and Mechanisms

Antibiotics: A Deeper Understanding of Their Actions and Mechanisms

Antibiotics are compounds that have the ability to kill or inhibit the growth of bacteria. They play a vital role in treating bacterial infections. A clear understanding of the classification, mechanisms of action, and characteristics of different antibiotics helps physicians make the most appropriate choice for each specific patient and condition.

Classification of Antibiotics:

• By chemical structure: This is the most common classification method, categorizing antibiotics based on their molecular structure.

• By origin:

• Antibiotics from microorganisms: Produced by organisms such as fungi and bacteria. Examples: Penicillin, Streptomycin.

• Semi-synthetic antibiotics: Produced by modifying the chemical structure of natural antibiotics. Examples: Ampicillin, Methicillin.

• Fully synthetic antibiotics: Produced entirely by chemical methods. Examples: Quinolone, Sulfonamide.

• By spectrum of activity:

• Broad-spectrum antibiotics: Effective against a wide range of bacteria. Examples: Tetracycline, Ciprofloxacin.

• Narrow-spectrum antibiotics: Effective only against specific types of bacteria. Examples: Penicillin G, Erythromycin.

• By mechanism of action:

• Bacteriostatic: Prevent the growth and development of bacteria. Examples: Tetracycline, Erythromycin.

• Bactericidal: Kill bacteria. Examples: Penicillin, Aminoglycoside.

Classification by chemical structure is considered the most scientific because it allows:

• Selection of antibiotics within the same group for substitution or rational antibiotic distribution during treatment.

Common antibiotic groups:

• Beta-Lactam Group:

• Penicillin:

• Penicillin G, A, M, V: Act on bacterial cell wall synthesis.

• Carboxypenicillin (Ticarcillin): Broader spectrum than Penicillin A, especially against Pseudomonas aeruginosa.

• Ureidopenicillin (Piperacillin): Broad spectrum, effective against intestinal bacteria and P. aeruginosa.

• Amidinopenicillin (Pivmecillinam): Used to treat urinary tract infections.

• Cephalosporin:

• First-generation cephalosporin: Mainly effective against Gram-positive bacteria.

• Second-generation cephalosporin: Effective against both Gram-positive and Gram-negative bacteria.

• Third-generation cephalosporin: Mainly effective against Gram-negative, less effective against Gram-positive.

• Fourth-generation cephalosporin: Used to treat infections caused by bacteria resistant to cephalosporins.

• Carbapenem (Imipenem): Broad spectrum, effective against multidrug-resistant bacteria.

• Monobactam (Aztreonam): No activity against Gram-positive bacteria.

• Beta-lactamase inhibitor drugs:

• Augmentin: Combines Amoxicillin + Clavulanate acid.

• Unasyn: Combines Ampicillin + Sulbactam.

• Timentin: Combines Ticarcillin + Clavulanate acid.

• Glycopeptide Group (Vancomycin, Teicoplanin): Act on bacterial cell wall synthesis.

• Protein synthesis inhibitor group:

• Aminoglycoside (Streptomycin, Gentamicin, Tobramycin, Neomycin): Bind to the 30S subunit of ribosomes.

• Cyclin (Tetracycline, Doxycycline, Minocycline): Bind to the 30S subunit of ribosomes.

• Macrolide (Erythromycin): Bind to the 50S subunit of ribosomes.

• Phenicol (Chloramphenicol): Bind to the 50S subunit of ribosomes.

• Nucleic acid synthesis inhibitor group:

• Quinolone (Nalidixic acid, Ciprofloxacin, Ofloxacin): Inhibit the enzyme DNA gyrase in bacteria.

• Rifamycin (Rifampicin): Inhibit DNA-dependent RNA polymerase in bacteria.

• Sulfonamide and Trimethoprim (Biseptol): Inhibit folic acid synthesis in bacteria.

• Nitro-imidazole (Metronidazol): Produce toxic products for bacterial DNA.

• Group acting on bacterial cytoplasm:

• Polypeptide (Polymycin, Bacitracin): Act on the cytoplasmic membrane.

• Nitrofurane: Act on the cytoplasmic membrane.

Mechanisms of antibiotic resistance in bacteria:

• Enzymatic production: Breakdown or modification of antibiotic molecules.

• Target site alteration: Bacteria alter the structure of the antibiotic’s target site.

• Reduced permeability of the cytoplasmic membrane: Bacteria decrease the permeability of the cytoplasmic membrane to antibiotics.

• Production of isoenzymes: Alter metabolism, reducing the antibiotic’s effects.

Forms of antibiotic resistance:

• Natural resistance: Bacteria are inherently insensitive to the antibiotic from the start.

• Acquired resistance: Bacteria acquire resistance genes after exposure to antibiotics.

• Pseudoresistance: Bacteria are inhibited by antibiotics but not killed.

Measures to limit the increase in antibiotic resistance:

• Use antibiotics selectively.

• Use antibiotics based on antibiogram results.

• Use antibiotics according to prescribed dosage, duration, and combination.

• Implement disinfection and sterilization measures.

• Monitor bacterial resistance patterns.

Conclusion:

A clear understanding of the classification, mechanisms of action, and characteristics of different antibiotics helps physicians make the most appropriate choice for each specific patient and condition. The rational use of antibiotics is critical to limit the increase in bacterial resistance, ensuring effective treatment and protecting public health.