BIO22 MICROBIOLOGY

• Biosafety


  Measures employed when handling bio-hazardous materials to avoid infecting oneself, others or the environment
• Containment


  • Safe methods for managing infectious agents in the laboratory where they are handled or maintained
  • Serves to reduce or eliminate exposure of laboratory workers, other persons, and outside environment to potentially hazardous agents
• Biosecurity


  Institutional and personal security measures designed to prevent the loss, theft, misuse, diversion or intentional release of pathogens and toxins
• Biohazard


  A potential hazard to humans, animals or the environment caused by a biological organism or material produced by such an organism
• Biohazards


  • Viruses
  • Bacteria
  • Fungi
  • Parasites and their products
  • Blood and body fluids
  • Tissues from humans and animals
  • Transformed cell lines
  • Certain types of nucleic acids
• Biosafety practices from 1913 textbook by Eyre


  • Wear gloves
  • Wash hands after working with infectious materials
  • Disinfect all materials after use
  • Use water to moisten specimen labels not saliva
  • Disinfect all contaminated materials before discarding
  • Report to appropriate personnel all accidents or exposures to infectious agents
• Safety extended to include


  • Fire safety
  • Electrical
  • Safe handling, storage, and disposal of chemicals and radioactive substances
  • Techniques for lifting or moving heavy objects
  • Disaster programs (earthquakes, hurricanes, snowstorms)
• Control Microorganism


  • Sterilization - kill all forms of microbial life including spores
  • Disinfection - destroy pathogenic organisms not all, or spores
  • Antiseptic - applied to the skin to eliminate or reduce the number of bacteria present; do not kill spores
• Medical materials classification


  • Critical - invade sterile tissues or enter vascular system; sporicidal
  • Semicritical - come in contact with mucus membranes; tuberculocidal
  • Noncritical - on skin
• Physical sterilization methods


  • Incineration; burned to ashes at 870-980℃
  • Moist heat - Steam under P, Medium at 121℃ for 15 mins, 15 PSI, Infectious medical waste at 132 for 30-60 mins
  • Boiling and pasteurization - 100℃ for 10 mins, Pasteurization in food industry for food-borne pathogens, 63℃ for 30 mins
  • Dry heat - Oven at 160-180℃ for 1.5 to 3 hrs
  • Filtration for heat sensitive materials
• Physical disinfection methods


  • Nonionizing radiation, UV light
  • Ionizing radiation - short wavelength and high energy gamma rays for disposables - plastic syringes, catheters, gloves before use
  • Microwaves
  • Radiograph machines
• Chemical disinfection methods

  • Alcohols - Ethanol and isopropanol
  • Aldehydes - 37% formalin, Formaldehyde vapor and vapor phase hydrogen peroxide, Glutaraldehyde
  • Halogens - Iodophors, Chlorine and it compounds
  • Detergents - Quaternary ammonium compounds, Phenolics, Chlorhexidine gluconate, Hexachlorophene, Chloroxylenol, Triclosan
  • Heavy metals - Bacteriostatic, Hg only in paints now, AgNO3
  • Gases - Ethylene oxide, Hydrogen peroxide, Periacetic acid
• Ethylene Dioxide is toxic as pure therefore mixed with nitrogen or carbon dioxide
• Ethylene Dioxide is used at 450 to 700 mg per liter of chamber space at 55-60℃ for 2hrs, killing mechanism is alkylation of NA in spore and vegetative cell
• Hydrogen peroxide is active against all vegetative microorganisms and bacterial and fungal spores
• Peracetic acid is gaseous and active against all vegetative microorganisms and bacterial and fungal spores
• Hydrogen peroxide and periacetic acid are shorter time and active against prions
• Resistance to disinfectants


  • Bacillus sp. etc. due to spores
  • Mycobacteria (acid fast)
  • Non-enveloped virus (e.g. polio virus)
  • Fungi
  • Vegetative nonsporulating bacteria
  • Gram negative rods
  • Enveloped virus
• Time depends on microbial load
• Removing organic material (blood, mucus) reduces microbial load
• 70% ROH more effective than 95% ROH due to increased water hydrolyzing bonds in protein molecules
• Aldehydes and glutaraldehyde produce irritating fumes
• Chlorine in the form of NaOCl sodium hypochlorite (household bleach) is used at 1:10 for blood spills on tables
• Iodine tincture with alcohol or iodophor is used as a disinfectant
• Mercury is toxic
• Hard water may reduce rate of killing microbes
• Amphyl- common lab disinfectant is a derivative of carbolic acid or phenol
• Detergent + disinfectant (carbolic) at 2% to 5% is used for cleaning bench tops
• Factors to consider in sterilizing

  • Type of organism - spore-formers, mycobacteria with lipid wall, viruses, biofilms, prions
  • Number of organism - microbial load
  • Concentration of disinfecting agent
  • Presence of organic matter (serum, blood)
  • Nature of surface to be disinfected
  • Contact time

  
• Glutaraldehyde is used longer as a sterilant, and shorter as a disinfectant
• Alcohol and iodine require at least 1-2 mins contact time
• Spores of bacteria and fungi require longer contact time than vegetative forms
• Phenol (carbolic acid)


  2% to 5% = for cleaning bench tops
• Factors to consider in sterilizing

  • Type of organism
  • Number of organism - microbial load
  • Concentration of disinfecting agent
  • Presence of organic matter (serum, blood)
  • Nature of surface to be disinfected
  • Contact time
  • Temperature
  • pH
  • Biofilms
  • Compatibility of disinfectant and sterilants

  
• Viruses


  • Susceptible to detergents and wetting agents
• Prions


  • Transmitted through contaminated medical products, therapeutic devices, body fluid, food products
  • Can withstand 121℃ in acid or base
  • Needs special methods
• Bleach (sodium hypochlorite) is inactive with blood, mucus, pus as it prevents full contact
• Remove organic matter to prevent inactivation of killing agent
• Glutaraldehyde


  Use longer as sterilant, shorter as disinfectant
• Alcohol and iodine


  At least 1-2 mins contact time