antimicrobial therapy

• selective toxicity 


  the ability of an antimicrobial agent to harm the microorganism cells without harming the cells of the host
• synthetic drugs


  artificial drug: an antibacterial substance that does not naturally occur
• antibiotics

  work by killing the bacteria or by making it hard for the bacteria to grow and multiply
• broad spectrum antibiotics


  class of antibiotics that act against an extensive range of disease-causing bacteria by targeting both gram-positive and gram-negative bacterial groups
• narrow spectrum antibiotics


  target only a few types of bacteria
• What makes a good drug?

  1. selective toxicity
  2. no hypersensitivity in host
  3. soluble in order to penetrate body tissues
  4. microbes should not readily develop resistance
  5. inexpensive
  6. doesn't require refrigeration
  7. easily administered
  8. tastes good
• cell wall targets

  pen., bacitracin
• ribosome targets

  streptomycin, tetracycline
• nucleic acid synthesis targets

  rifampicin
• enzymes target

  sulfa drugs
• plasma membrane targets

  polymyxin B, nystatin
• Drug resistance

  The microbe becomes resistant, not the host. through a process of selection. In an environment where antibiotics are present, the sensitive microbes die off while the resistant ones thrive. This process of natural selection leads to the evolution of the microbe.
• dangers of using antibiotics

  1.encourages resistance in many populations, pathogens and normal flora. transmission of these genes particularly by microbial conjugation will distribute these genes further 2. normal flora is disturbed, allowing for superinfection
• superinfection

  infection occurring after or on top of an earlier infection, especially following treatment with broad-spectrum antibiotics
• A few years ago, one medical journal reported on a survey of antibiotic use in one hospital. The results indicated that more than 60% of the antibiotics prescribed there were either given in the wrong dosage or used in applications for which they would not be effective.
• How do we reduce the use of antibiotics?


  1.Use antibiotics only when necessary 2.Use all of the antibiotics for the fully prescribed time 3. Some infections need to be treated with multiple antimicrobial drugs
• Why is important to use all of your antibiotics for the fully prescribed time?

  Interrupting antibiotic therapy early will allow the more resistant portion of the pathogen population to survive.
• Why are some infections treated with multiple antimicrobial drugs?


  The likelihood that a cell would simultaneously convert to resistance to all four drugs is quite low thus dis-allowing any out growth of resistant cells.