MC 3 - Microbiology & Parasitology

• Microbiology


  The study of microscopic organisms
• Parasitology


  The study of parasites, their hosts, and the relationship between them
• Immunology


  The study of the immune system and its functions
• Ecological relationships


  • Competition
  • Predation
  • Commensalism
  • Mutualism
  • Parasitism
  • Symbiosis
• Commensalism


  A relationship in which one organism benefits while the other is neither helped nor harmed
• Parasitism


  A relationship in which one organism benefits at the expense of another
• Mutualism


  A relationship in which both organisms benefit from each other
• Factors promoting growth and development of micro-organisms
• Importance of Micro-organisms
• Classification of micro-organisms
• History: Humans vs. Microbes, infections, diseases, plagues, epidemics, pandemics
• Bubonic Plague or the Black Death
• Epidemic swept through Europe in the Middle Ages (13th and 14th centuries)
• About 40 million people were killed, about 1/3 of the population of the continent
• Etiological agent: Yersinia pestis, Gram (-) rod
• Vectors: Rat and Flea
• Bubonic Plague Infection


  1. Flea bite with Yersinia pestis

  2. Bacteria multiply in the bloodstream

  3. Bacteremia

  4. Bacteria localize in lymph nodes, especially axillary and groin areas

  5. Hemorrhaging occurs in lymph nodes, resulting in "black and blue" swellings or Buboes

  6. If untreated, about 50% Mortality Rate

  7. If bacteria spread to the lungs, it becomes Pneumonic Plague and is highly contagious (Almost a 99% Mortality Rate)
• "I wouldn't touch it with a 10' pole"
• Most of history, microbes have been winning the battle
• In the last 100 years or so, the battle has swung in our favor
• Reason for the swing in our favor: Increasing knowledge of how to control microbial growth
• Smallpox, Variola virus, Eradicated in 1977 (Somalia)
• Methods to Control Microbial Growth

  1. Physical

  2. Chemical
• Terms used


  • Sterilization vs. Disinfection
  • Disinfectant vs. Antiseptic
• Sterilization


  Destroying all forms of life
• Disinfection


  Destroying pathogens or unwanted organisms
• Disinfectant


  Antimicrobial agent used on inanimate objects
• Antiseptic


  Antimicrobial agent used on living tissues
• Antiseptic


  Antimicrobial agent used on living tissue
• Cidal


  Kills
• Static


  Inhibits growth
• Types of agents


  • Disinfectant
  • Antiseptic
• Types of effects


  • Cidal
  • Static
• Targets of Antimicrobial Agents

  • Cell membrane
  • Enzymes & Proteins
  • DNA & RNA
• Physical Methods of Microbial Control

  1. Heat

  2. Moist Heat

  3. Dry Heat

  4. Filtration
• Moist Heat


  1. Boiling Water kills vegetative bacterial cells, Fungi and many viruses

  2. Not effective for endospores and some viruses

  3. Some spores may survive boiling water for up to 20 hrs
• Autoclave (Steam under pressure)


  1. Preferred method of sterilization

  2. Water boils at 100 C

  3. Increasing the pressure raises the Temp.

  4. 121 C for 15 min.
• Kilit Ampule


  Spores of Bacillus stearothermophilus fermentable sugar pH indicator basic - red acid - yellow
• Dry Heat


  1. Direct Flaming - Inoculating Loop and Needle 100% effective

  2. Incineration - disposable wastes (paper cups, bags, dressings)

  3. Hot Air Sterilization - Oven (170 C for 2 hours) used on substances that would be damaged by moist heat sterilization gauzes, dressings or powders
• Filtration


  Removes microorganisms from solutions that might be damaged by heat culture media