براء ١

• Antimicrobial drugs

  Effective in the treatment of infections because of their selective toxicity
• Selection of Antimicrobial Agents

  1. Identification of the infecting organism

  2. Empiric therapy prior to identification of the organism

  3. Determination of antimicrobial susceptibility of infective organisms

  
• Bacteriostatic drugs

  Arrest the growth & replication of bacteria

  
• Bactericidal drugs

  Kill bacteria
• Minimum inhibitory concentration (MIC)


  Lowest concentration of antibiotic that inhibits bacterial growth

  
• Minimum bactericidal concentration (MBC)


  Minimal concentration of antibiotic that kills the bacteria

  
• Effects of bactericidal and bacteriostatic drugs on the growth of bacteria in vitro

  
• Site of infection


  • Penetration & concentration of an antibacterial agent in the CSF is particularly influenced by lipid solubility, molecular weight, and protein binding of the drug

  
• Patient factors

  • Immune system
  • Renal dysfunction
  • Hepatic dysfunction
  • Poor perfusion
  • Age
  • Pregnancy
  • Lactation
• Concentration-dependent killing

  Certain antimicrobial agents, including aminoglycosides & fluoroquinolones, show significant increase in the rate of bacterial killing as the concentration of antibiotics increases from 4 to 64 fold the MIC

  
• Post-antibiotic effect (PAE)

  Persistent suppression of microbial growth that occurs after levels of antibiotic have fallen below the MIC

  
• Chemotherapeutic Spectra

  • Narrow spectrum antibiotics
  • Extended spectrum antibiotics
  • Broad spectrum antibiotics

  
• Reasons for combinations of antimicrobial drugs


  • To provide broad spectrum empirical therapy
  • To treat polymicrobial infections
  • To decrease the emergence of resistant strains
  • To decrease dose related toxicity
  • To obtain enhanced inhibition or killing

  
• Genetic alterations leading to drug resistance

  • Spontaneous mutations of DNA
  • DNA transfer of drug resistance
• Altered expression of proteins in drug resistant organisms

  • Modification of target sites
  • Decreased accumulation
  • Enzymatic inactivation
• Prophylactic Antibiotics


  • Prevention of streptococcal infections in patients with a history of rheumatic heart disease
  • Pretreatment of patients undergoing dental extractions
  • Prevention of tuberculosis or meningitis
  • Treatment prior to certain surgical procedures
  • Treatment of the mother with zidovudine
• Complications of Antibiotic Therapy

  • Hypersensitivity reactions
  • Direct toxicity
  • Super infections

  
• Classification of some antibacterial agents by their sites of action