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Control of Microbial Growth. Chapter 7. History. Humans vs. Microbes infections diseases plagues epidemics pandemics. Nursery Rhyme. Ring- a - ring of rosies Pocketful of posies Achoo ! Achoo ! We all fall down. Bubonic Plague or the Black Death.

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history
History
  • Humans vs. Microbes
    • infections
    • diseases
    • plagues
    • epidemics
    • pandemics
slide3

Nursery Rhyme

Ring- a - ring of rosies

Pocketful of posies

Achoo ! Achoo !

We all fall down.

bubonic plague or the black death
Bubonic Plague or the Black Death
  • Epidemic swept thru Europe in the Middle Ages (13th and 14th centuries)
  • 40 million people were killed
    • About 1/3 of the population of the continent
  • Etiological agent:
    • Yersinia pestis Gram (-) rod
  • 2 Vectors
    • Rat
    • Flea
bubonic plague infection
Bubonic Plague Infection
  • 1. Flea bite with Yersinia pestis
  • 2. Bacteria multiply in the bloodstream
    • Bacteremia
  • 3. Bacteria localize in lymph nodes, especially axillary and groin areas
slide7

4. Hemorrhaging occurs in lymph nodes, resulting in “black and blue” swellings or Buboes (hence the name Bubonic Plague or Black Death)

bubonic plague infection1
Bubonic Plague Infection
  • 5. If untreated, about 50 % Mortality Rate
  • 6. If bacteria spread to the lungs, it becomes Pneumonic Plague and is now highly contagious (Almost a 99 % Mortality Rate)
slide9

Nursery Rhyme

Ring - a - ring of rosies,

A pocketful of posies

Achoo ! Achoo !

We all fall down.

humans vs microbes
Humans vs. Microbes
  • 1. Most of History, microbes have been winning the battle
  • 2. In the last 100 yrs or so the battle has swung in our favor
    • Why?
      • Because of our increasing knowledge of how to Control Microbial Growth
slide12

Smallpox

Variola virus

Eradicated in 1977 (Somalia)

terms used
Terms used:
  • Sterilization vs. Disinfection
  • Sterilization
    • destroying all forms of life
  • Disinfection
    • destroying pathogens or unwanted organisms
slide15
Disinfectant vs. Antiseptic
  • Disinfectant
    • antimicrobial agent used on inanimate objects
  • Antiseptic
    • antimicrobial agent used on living tissue
cidal vs static
cidal vs. static
  • Bactericidal - kills bacteria
  • Bacteristatic - inhibits bacterial growth
  • Fungicidal
  • Fungistatic
  • Algacidal
  • Algastatic
factors that effect antimicrobial activity
Factors that effect Antimicrobial Activity
  • 1. Temp
  • 2. Time
  • 3. Concentration of Antimicrobial agent
  • 4. Type of Microbe
  • 5. Activity of Microbe
  • 6. Presence of organic matter
targets of antimicrobial agents
Targets of Antimicrobial Agents
  • 1. Cell membrane
  • 2. Enzymes & Proteins
  • 3. DNA & RNA
physical methods of microbial control
Physical Methods of Microbial Control
  • 1. Heat
    • works by denaturing enzymes and proteins
  • A. Thermal Death Point (TDP)
    • lowest temp. at which all microorganism in a liquid culture are killed in 10 minutes
  • B. Thermal Death Time (TDT)
    • minimum length of time in which all microorganisms in a liquid culture are killed at a given temperature
moist heat
Moist Heat
  • 1. Boiling Water
    • kills vegetative bacterial cells, Fungi and many viruses
    • not effective for endospores and some viruses
    • Hepititis (20 min)
    • Some spores may survive boiling water for up to 20 hrs
moist heat1
Moist Heat
  • 2. Autoclave (Steam under pressure)
    • preferred method of sterilization
    • Water boils at 100 C
    • Increasing the pressure raises the Temp.
    • 15 lbs./ per sq. inch (psi) ------> 121 C
    • 121 C for 15 min.
kilit ampule
Kilit Ampule
  • Spores of Bacillus stearothermophilus
  • fermentable sugar
  • pH indicator
    • basic - red
    • acid - yellow
dry heat
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
Filtration
  • Removes microorganisms from solutions that might be damaged by heat
    • culture media
    • enzymes
    • vaccines
    • antibiotics
radiation
Radiation
  • 1. Ionizing Radiation
    • gamma rays & x-rays
      • penetrates most substances
  • Used on substances that could be damaged by heat
    • plastic petri dishes
    • plastic syringes
    • catheters
    • surgical gloves
radiation1
Radiation
  • 2. Non-Ionizing Radiation
    • UV Light
      • does not penetrate plastic, glass or proteinaceous matter
  • Used to reduce microbial populations
    • hospital rooms
    • nurseries
    • operating rooms

Thymine Dimers

pasteurization
Pasteurization
  • Disinfection - not sterilization (removes unwanted organisms)
  • Mycobacterium tuberculosis
  • 63 C for 30 minutes
  • 72 C for 15 seconds (HTST)
  • Thermodurics
    • able to survive high temps.
methods used to control microbial growth
Methods used to control Microbial Growth
  • 1. Heat
    • Moist Heat
      • Boiling Water
      • Steam Heat (Autoclave)
    • Dry Heat
      • Direct Flaming
      • Incineration
      • Hot Air Sterilization (Oven)
  • 2. Filtration
  • 3. Radiation
    • Ionizing Radiation
    • Non-Ionizing Radiation
  • 4. Pasteurization (Heat)