Immunology

    Cards (23)

    • Antibiotics
      A substance produced by a fungus which diminishes the population growth of bacteria
    • Mode of action of antibiotics
      1. Bacteriostatic - prevent the population growth of bacteria
      2. Bactericidal - kill bacteria
    • Antibiotics
      • Act on bacteria, but not on eukaryotic cells or viruses
      • Can treat bacterial infection without harm to the patient
    • Types of antibiotics
      • Broad-spectrum - act against a wide range of disease-causing bacteria by targeting both gram-positive and gram-negative bacterial groups
      • Narrow-spectrum - active against a selected group of bacterial types, can act on either gram-positive or gram-negative but not both
    • Bacterial cell wall structure
      Contains peptidoglycan consisting of molecules of polysaccharide cross-linked by amino acid side chains, providing strength and preventing osmotic lysis<|>Some bacteria have an outer layer of lipopolysaccharides, which highlights them as Gram negative and provides protection from some antibacterial agents
    • Tetracycline
      A broad-spectrum, bacteriostatic antibiotic that affects protein synthesis<|>Acts as a competitive inhibitor, blocking the second tRNA binding site in the large subunit of bacterial ribosomes, preventing the binding of a tRNA molecule's anticodon to its complementary codon
    • Tetracycline binding to bacterial ribosomes

      Prevents the binding of tRNA molecules, inhibiting protein synthesis and preventing bacterial growth and replication
    • Penicillin
      Does not affect gram-negative bacteria
    • Penicillin
      • Narrow-spectrum, bactericidal antibiotic
      • Affects the formation of cross-linkages in the peptidoglycan cell wall during growth and division of bacterial cells
      • Binds irreversibly to transpeptidase enzyme and permanently alters its function
    • Penicillin is a non-competitive inhibitor
    • Penicillin has a shape that is not complementary to the active site

      The enzyme's function is permanently altered
    • Cell wall is weakened
      If placed in a hypotonic solution, the cells would lyse (burst) as the cell contents enter the higher concentration outside
    • Gram-positive bacteria

      • More susceptible to penicillin due to their thick peptidoglycan cell wall
    • Gram-negative bacteria

      • Less susceptible to penicillin due to their thin peptidoglycan cell wall and outer lipopolysaccharide layer
    • Viruses are not affected by antibiotics as they have no cell wall or metabolic pathways to disrupt
    • Antibiotics
      Used extensively to treat infections in people and to prevent infections in farmed animals
    • Sources of antibiotic resistance alleles
      1. Bacteria divide under optimum conditions and have a high mutation rate. Naturally occurring mutations that confer resistance to antibiotics give these bacteria a selective advantage in the presence of antibiotics.
      2. Plasmids containing the antibiotic resistance allele can be transferred from one bacterium to another via conjugation.
    • Overuse of antibiotics
      Results in the accidental selection of bacterial strains that are completely unaffected by some antibiotics
    • If there are no antibiotics in the environment
      Having resistance would not provide the bacteria with a selective advantage over bacteria without resistance
    • Overuse of antibiotics
      Selects for resistant bacteria and the frequency of the resistance allele increases
    • Clinically important bacteria showing antibiotic resistance
      • Leprosy
      • TB
      • Gonorrhoea
    • Antibiotic resistant bacteria
      • MRSA (Methicillin-resistant Staphylococcus aureus)
      • Clostridium difficile
    • Methods of prevention and control for the emergence of antibiotic resistance
      • Antibiotics should only be prescribed when needed.
      • Patients should finish the complete course of antibiotics.
      • Introduction of infection control in hospitals.