control of microbial growth

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this is a series of lectures on microbiology for undergraduate medical and paramedical students

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control of microbial growth

  1. 1. Control of Microbial Growth Dr. Ashish Jawarkar Pathologist Parul Sevashram Hospital
  2. 2. History Humans vs. Microbes • • • • • infections diseases plagues epidemics pandemics
  3. 3. Nursery Rhyme Ring- a - ring of rosies Pocketful of posies Achoo ! Achoo ! We all fall down.
  4. 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 2 Vectors • Rat • Flea Gram (-) rod
  5. 5. Yersinia pestis - Gram (-) bacillus Vectors - Rat and Flea
  6. 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. 7. 4. Hemorrhaging occurs in lymph nodes, resulting in “black and blue” swellings or Buboes (hence the name Bubonic Plague or Black Death)
  8. 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. 9. Nursery Rhyme Ring - a - ring of rosies, A pocketful of posies Achoo ! Achoo ! We all fall down.
  10. 10. “ I wouldn’t touch it with a 10’ pole”
  11. 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. 12. Smallpox Variola virus Eradicated in 1977 (Somalia)
  13. 13. Methods to Control Microbial Growth 1. Physical 2. Chemical
  14. 14. Terms used: Sterilization vs. Disinfection Sterilization • destroying all forms of life Disinfection • destroying pathogens or unwanted organisms
  15. 15. Disinfectant vs. Antiseptic Disinfectant • antimicrobial agent used on inanimate objects Antiseptic • antimicrobial agent used on living tissue
  16. 16. cidal vs. static Bactericidal - kills bacteria Bacteristatic - inhibits bacterial growth Fungicidal Fungistatic Algacidal Algastatic
  17. 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. 18. 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
  19. 19. 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
  20. 20. 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.
  21. 21. 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
  22. 22. Filtration Removes microorganisms from solutions that might be damaged by heat • • • • culture media enzymes vaccines antibiotics
  23. 23. 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
  24. 24. 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
  25. 25. 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.
  26. 26. 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)
  27. 27. Portals of Entry 1. Mucus Membranes 2. Skin 3. Parentarel
  28. 28. 1. Mucus Membranes A. Respiratory Tract • microbes inhaled into mouth or nose in droplets of moisture or dust particles • Easiest and most frequently traveled portal of entry
  29. 29. Common Diseases contracted via the Respiratory Tract Common cold Flu Tuberculosis Whooping cough Pneumonia Measles Strep Throat Diphtheria
  30. 30. Mucus Membranes B. Gastrointestinal Tract • microbes gain entrance thru contaminated food & water or fingers & hands • most microbes that enter the G.I. Tract are destroyed by HCL & enzymes of stomach or bile & enzymes of small intestine
  31. 31. Common diseases contracted via the G.I. Tract Salmonellosis • Salmonella sp. Shigellosis • Shigella sp. Cholera • Vibrio cholorea Ulcers • Helicobacter pylori Botulism • Clostridium botulinum
  32. 32. Fecal - Oral Diseases These pathogens enter the G.I. Tract at one end and exit at the other end. Spread by contaminated hands & fingers or contaminated food & water Poor personal hygiene.
  33. 33. Mucus Membranes of the Genitourinary System - STD’s Gonorrhea Neisseria gonorrhoeae Syphilis Treponema pallidum Chlamydia Chlamydia trachomatis HIV Herpes Simplex II
  34. 34. Mucus Membranes D. Conjunctiva – • mucus membranes that cover the eyeball and lines the eyelid Trachoma • Chlamydia trachomatis
  35. 35. 2nd Portal of Entry: Skin Skin - the largest organ of the body. When unbroken is an effective barrier for most microorganisms. Some microbes can gain entrance thru openings in the skin: hair follicles and sweat glands
  36. 36. 3rd Portal of Entry: Parentarel Microorganisms are deposited into the tissues below the skin or mucus membranes Punctures injections bites scratches surgery splitting of skin due to swelling or dryness
  37. 37. Preferred Portal of Entry Just because a pathogen enters your body it does not mean it’s going to cause disease. pathogens - preferred portal of entry
  38. 38. Preferred Portal of Entry Streptococcus pneumoniae • if inhaled can cause pneumonia • if enters the G.I. Tract, no disease Salmonella typhi • if enters the G.I. Tract can cause Typhoid Fever • if on skin, no disease

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