ANTIBIÓTICOS, GENERALIDADES, CLASIFICACIÓN - MNEMOTECNIAS | FARMACOLOGÍA | P1

Introduction to Antibiotics and Pharmacology

Overview of the Series

• David Vargas introduces a new video series focused on pharmacology, specifically antibiotics, aiming to provide clear and simple explanations.

• The content will cover mechanisms of action, bacterial resistance, and include mnemonic tips for better retention. This topic is frequently questioned by professors.

Greetings and Acknowledgments

• Vargas sends greetings to viewers from various countries including Argentina, Colombia, Bolivia, and Spain. He acknowledges students from multiple universities who have requested these videos.

Understanding Antibiotics

Definition of Key Terms

• An antibiotic is defined as a chemical substance that can inhibit or destroy invading microorganisms without causing toxic effects on the host. This is considered the ideal definition.

• The term "antimicrobial" encompasses both antibiotics and chemotherapeutics; antibiotics are produced by other microorganisms while chemotherapeutics are synthetically made substances.

Mechanisms of Action

• There are five primary mechanisms through which antibiotics act:

• Inhibition of cell wall synthesis.

• Disruption of protein synthesis.

• Interference with nucleic acids.

• Alteration of metabolic pathways.

• Membrane disruption. These can be remembered using various mnemonic devices related to numbers (e.g., five fingers).

Bacterial Structure and Function

Bacterial Cell Components

• Bacteria possess a cellular membrane, cytoplasm, nucleus area containing genetic material, and ribosomes for protein production; they also have a protective cell wall that plays a crucial role in their survival against external pressures.

Importance of Cell Wall Integrity

• The cell wall protects bacteria from osmotic pressure; if damaged (e.g., by inhibiting its synthesis), it can lead to bacterial lysis due to internal pressure differences between the inside and outside environments. Thus, drugs targeting cell wall synthesis are bactericidal (kill bacteria).

Mechanisms Behind Cell Wall Synthesis

Steps in Peptidoglycan Formation

• Four key steps are involved in peptidoglycan formation:

• Subunit assembly outside the bacterial cell.

• Transporting these subunits into the cell via specific proteins.

• Final assembly within the bacterial membrane leading to structural integrity.

Mechanisms of Antibiotic Action

Transport Inhibition by Antibiotics

• The C-55 protein acts as a transporter that can be blocked, preventing it from returning to the bacteria to bring subunits outside.

• Vancomycin plays a crucial role in inhibiting transport by blocking the delivery of subunits necessary for bacterial function.

• Certain antibiotics can inhibit enzymes responsible for binding subunits, affecting the overall transport process within bacteria.

Groups of Pharmacological Agents

• Various pharmacological groups, including beta-lactams (penicillins, cephalosporins), block transportation and precursor synthesis essential for bacterial growth.

• Membrane integrity is vital for bacteria; damaging it can lead to cell death. Polymyxins and daptomycin are examples of drugs that disrupt membrane function.

Protein Synthesis Inhibition

• Protein synthesis involves three phases: initiation, elongation, and termination. Antibiotics target these processes differently.

• Tetracyclines block the 30S ribosomal subunit during initiation, while aminoglycosides alter mRNA codons affecting translation accuracy.

Mechanisms Affecting Ribosomal Function

• Chloramphenicol prevents amino acid addition during protein synthesis; macrolides cause premature termination of peptide chains leading to dysfunctional proteins.

Interference with Nucleic Acid Synthesis

• DNA replication and transcription are critical processes targeted by antibiotics like quinolones (inhibiting DNA gyrase) and rifampicin (blocking RNA polymerase).

• Metronidazole interferes directly with DNA function through its metabolites, impacting bacterial viability without being bactericidal.

Folate Synthesis Inhibition

Understanding Folic Acid Metabolism in Eukaryotes and Bacteria

The Role of Folic Acid

• Eukaryotic organisms require external folic acid, while bacteria can synthesize it internally due to their metabolic pathways.

• Bacteria produce dihydrofolate through the enzyme dihydropteroate synthase, which is crucial for synthesizing tetrahydrofolate via dihydrofolate reductase.

Importance of Folic Acid in Nucleotide Synthesis

• Folic acid is essential for purine and pyrimidine synthesis; blocking its pathway inhibits DNA and RNA production, affecting bacterial growth.

• Antibiotics can disrupt these metabolic pathways in bacteria, leading to their effectiveness against bacterial infections.

Mnemonic for Remembering Antibiotics

• A mnemonic device is introduced: "Pecamos fácil al bailar la bamba," emphasizing the importance of remembering antibiotics.