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Control of Microbial Growth

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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Control of Microbial Growth

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  1. Control of Microbial Growth Chapter 7

  2. History • Humans vs. Microbes • infections • diseases • plagues • epidemics • pandemics

  3. Nursery Rhyme Ring- a - ring of rosies Pocketful of posies Achoo ! Achoo ! We all fall down.

  4. 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

  5. Yersinia pestis - Gram (-) bacillus Vectors - Rat and Flea

  6. 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

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

  8. 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)

  9. Nursery Rhyme Ring - a - ring of rosies, A pocketful of posies Achoo ! Achoo ! We all fall down.

  10. “ I wouldn’t touch it with a 10’ pole”

  11. 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

  12. Smallpox Variola virus Eradicated in 1977 (Somalia)

  13. Methods to Control Microbial Growth • 1. Physical • 2. Chemical

  14. Terms used: • Sterilization vs. Disinfection • Sterilization • destroying all forms of life • Disinfection • destroying pathogens or unwanted organisms

  15. Disinfectant vs. Antiseptic • Disinfectant • antimicrobial agent used on inanimate objects • Antiseptic • antimicrobial agent used on living tissue

  16. cidal vs. static • Bactericidal - kills bacteria • Bacteristatic - inhibits bacterial growth • Fungicidal • Fungistatic • Algacidal • Algastatic

  17. 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

  18. Targets of Antimicrobial Agents • 1. Cell membrane • 2. Enzymes & Proteins • 3. DNA & RNA

  19. 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

  20. 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

  21. 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.

  22. Kilit Ampule • Spores of Bacillus stearothermophilus • fermentable sugar • pH indicator • basic - red • acid - yellow

  23. 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

  24. Filtration • Removes microorganisms from solutions that might be damaged by heat • culture media • enzymes • vaccines • antibiotics

  25. 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

  26. 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

  27. 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.

  28. 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)

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