26-35

• What is antimicrobial chemotherapy?

  Use of agents to treat infections
• What does the term "antibacterial spectrum" refer to?

  Range of activity an antimicrobial agent has
• What is a broad-spectrum antibacterial drug?

  Inhibits a variety of gram-positive and gram-negative bacteria
• What is a narrow-spectrum drug?

  Active only against a limited variety of bacteria
• What is bacteriostatic activity?

  Inhibits the growth of an organism
• What does MIC stand for?

  Minimum inhibitory concentration
• What is bactericidal activity?

  Kills the test organism
• What does MBC stand for?

  Minimum bactericidal concentration
• Why are antibiotic combinations used?

  To broaden spectrum, prevent resistance, achieve synergy
• What is antibiotic synergism?

  Enhanced bactericidal activity from combined antibiotics
• What is antibiotic antagonism?

  One antibiotic interferes with another's activity
• What are the four basic mechanisms of antibiotic action?

  Inhibition of cell wall, protein, nucleic acid synthesis, antimetabolites
• What are the characteristics of antibiotics that inhibit cell wall synthesis?

  • Bind to Penicillin Binding Proteins (PBPs)
  • Inhibit peptidoglycan assembly
  • Activate autolysins to degrade cell wall
  • Most are bactericidal agents
• What is the common structure shared by β-Lactam antibiotics?

  β-lactam ring structure
• What are natural penicillins active against?

  β-hemolytic streptococci and most gram-positive anaerobes
• What is the primary use of Penicillin G?

  Used intravenously due to poor GIT absorption
• What is the advantage of penicillinase-resistant penicillins?

  Enhanced activity against penicillinase-producing staphylococci
• What are aminopenicillins effective against?

  Some gram-negative rods and gram-positive cocci
• What is the role of β-lactamase inhibitors?

  Inactivate bacterial β-lactamases to enhance antibiotic efficacy
• What is the mechanism of action of vancomycin?

  Inhibits cross-linkage of peptidoglycan layers
• Why is daptomycin ineffective against gram-negative bacteria?

  Cannot penetrate their cell wall
• What is the primary action of polymyxins?

  Increase cell permeability and cause cell death
• What is isoniazid used for?

  Treatment of mycobacterial infections
• How do aminoglycosides inhibit protein synthesis?

  By irreversibly binding to 30S ribosomal proteins
• What is the effect of tetracyclines on protein synthesis?

  Blocks binding of tRNA to ribosome-mRNA complex
• What is the primary action of macrolides?

  Blocks polypeptide elongation during protein synthesis
• What is the mechanism of action of chloramphenicol?

  Binds to peptidyl transferase of the 50S ribosomal subunit
• What is the effect of linezolid on protein synthesis?

  Blocks initiation complex formation in protein synthesis
• What are the characteristics of aminoglycosides?

  • Irreversibly bind to 30S ribosomal proteins
  • Bactericidal antibiotics
  • Primarily treat gram-negative rod infections
  • Require co-administration with cell wall inhibitors for some organisms
• What are the characteristics of tetracyclines?

  • Bind reversibly to 30S ribosomal subunits
  • Broad-spectrum bacteriostatic antibiotics
  • Active against gram-positive and some gram-negative bacteria
• What are the characteristics of macrolides?

  • Reversibly bind to 23S rRNA of 50S ribosomal subunit
  • Broad-spectrum bacteriostatic antibiotics
  • Active against gram-positive and some gram-negative bacteria
• What are the characteristics of lincosamides?

  • Block protein elongation by binding to 50S ribosome
  • Active against staphylococci and anaerobic gram-negative rods
  • Generally inactive against aerobic gram-negative bacteria
• What are the characteristics of streptogramins?

  • Block protein synthesis by binding to 50S ribosomal subunit
  • Active against gram-positive bacteria
  • Used for treating multidrug-resistant infections
• What are the characteristics of oxazolidinones?

  • Block initiation of protein synthesis
  • Narrow-spectrum antibiotics
  • Active against multidrug-resistant gram-positive bacteria
• What are the characteristics of glycylcyclines?

  • Inhibit protein synthesis like tetracyclines
  • Broad spectrum, more active against gram-negative bacteria
  • Less affected by efflux or enzymatic modification
• What are the characteristics of chloramphenicol?

  • Binds to peptidyl transferase of 50S ribosomal subunit
  • Broad antibacterial spectrum
  • Can cause aplastic anemia
• What are the characteristics of ketolides?

  • Semisynthetic derivatives of erythromycin
  • Broad-spectrum antibiotics
  • Active against respiratory pathogens and intracellular pathogens
• What are the characteristics of daptomycin?

  • Binds irreversibly to cytoplasmic membrane
  • Causes membrane depolarization and cell death
  • Active against multidrug-resistant gram-positive bacteria
• What are the characteristics of polymyxins?

  • Insert into bacterial membranes
  • Active against gram-negative rods
  • Can cause nephrotoxicity
• What are the characteristics of antimyobacterial agents?

  • Used for mycobacterial infections
  • Include isoniazid, ethambutol, cycloserine, ethionamide
  • Bactericidal against actively replicating mycobacteria