control of microbial growth
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control of microbial growth

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

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

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  • 1. Control of Microbial Growth Dr. Ashish Jawarkar Pathologist Parul Sevashram Hospital
  • 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 2 Vectors • Rat • Flea Gram (-) rod
  • 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. 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. 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. 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. 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. Filtration Removes microorganisms from solutions that might be damaged by heat • • • • culture media enzymes vaccines antibiotics
  • 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. 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. 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. 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. Portals of Entry 1. Mucus Membranes 2. Skin 3. Parentarel
  • 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. Common Diseases contracted via the Respiratory Tract Common cold Flu Tuberculosis Whooping cough Pneumonia Measles Strep Throat Diphtheria
  • 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. Common diseases contracted via the G.I. Tract Salmonellosis • Salmonella sp. Shigellosis • Shigella sp. Cholera • Vibrio cholorea Ulcers • Helicobacter pylori Botulism • Clostridium botulinum
  • 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. Mucus Membranes of the Genitourinary System - STD’s Gonorrhea Neisseria gonorrhoeae Syphilis Treponema pallidum Chlamydia Chlamydia trachomatis HIV Herpes Simplex II
  • 34. Mucus Membranes D. Conjunctiva – • mucus membranes that cover the eyeball and lines the eyelid Trachoma • Chlamydia trachomatis
  • 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. 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. 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. 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