Micro ch 5

  1. Who was responsible for revolutionizing surgery by introducing methods that prevent wounds from becoming infected
    Joseph Lister
  2. Sterilization
    • the removal or destruction of all microorganisms and viruses on or in a product
    • Destruction means they cannot be "revived" to multiply even when transferred from the sterilized product to an ideal growth medium
    • *Sterile DOES NOT consider prions, as they are not destroyed by standard sterilization
  3. disinfection
    • the elimination of most or all pathogens on or in a material
    • Generally implies use of antimicrobial chemicals
    • Unlike sterilization, disinfection suggests that some living microbes may remain
  4. disinfectants
    • are antimicrobial chemicals used for disinfecting inanimate objects
    • toxic to many forms of life and therefore biocides (bio means life, cida means to kill)
    • Often called germicides
    • Target microorganisms and viruses
  5. bactericidal
    • another term for disinfectant and germicide
    • meaning they kill bacteria
  6. Antiseptics
    • antimicrobial chemicals non-toxic enough to use on skin or other body tissue
    • routinely used to decrease bacterial numbers on skin before invasive procedures such as surgery
  7. Decontamination
    • process used to reduce the number of pathogens to a level considered safe to handle
    • tx can be as simple as thorough washing, or it may involve the use of heat or disinfectants
  8. Sanitization
    • generally implies a process that substantially reduces the microbial pop to meets accepted health standards
    • most people also expect a sanitized object to look clean
    • *this term does not indicate any specific level of control
  9. Preservation
    • the process of delaying spoilage of foods or other perishable products
    • One way is to adjust storage conditions to slow microbial growth
    • Another is to add chemical preservatives
  10. bacteriostatic
    • inhibits the growth of bacteria but do not kill them
    • Ex: a chemical
  11. aseptic technique
    use of specific methods to prevent microorganisms from contaminating an environment
  12. Disinfection by-products (DBP's)
    occurs when chlorine and other disinfectants react with naturally occurring chemicals in the water
  13. D value
    • Decimal reduction time
    • the time required for killing 90% of a bacterial population under specific conditions
    • Temp for the process is indicated by a subscript (Ex: D121)
  14. Why is it important to thoroughly clean items before disinfection or sterilization
    dirt, grease, and body fluids such as blood can interfere with heat penetration and the action of chemicals disinfectants
  15. Risk for infection: how are medical instruments categorized for cleaning?
    • According to their risk for transmitting infectious agents; those that pose greater threats require more rigorous germicidal procedures.
    • Groups include:
    • Critical instruments- direct contact with body tissues, like needles and scalpels. These are critical instruments that must be sterile
    • Semicritical instruments- come into contact with mucous membranes, but don't penetrate body tissue. Include GI scopes
    • Non-critical instruments and surfaces- come into contact with only unbroken skin so little risk. Includes countertops, stethoscopes, and BP cuffs
  16. Physical methods for destroying microbes and viruses
    • Moist Heat
    • Dry heat
    • Filtration
    • Radiation
    • High Pressure
  17. Moist heat
    • Denatures proteins.
    • Relatively fast, reliable, safe, and inexpensive
    • Includes:
    • Boiling
    • Pasteurization
    • Pressurized steam (autoclaving)
  18. Boiling
    • Boiling for 5 minutes destroys most microorganisms and viruses
    • a notable exception is endospores
    • *5 min boiling can be used to treat drinking water
  19. Pasteurization
    • Developed by Louis Pasteur, as a way to prevent wine spoilage
    • foods and inanimate objects can be pasteurized
    • Significantly decreases the numbers of heat-sensitive microorganisms, including spoilage microbes and pathogens (except sporeformers)
  20. HTST
    • High-temp-short-time
    • The way most pasteurization is done today
    • Milk is pasteurized by heating to 72° C for 15 sec. 
    • Parameters must be adjusted to product. Ex: Ice cream is rich in fats so it is pasteurized at 82°C for 20 sec
  21. UHT
    • Ultra-High-Temp
    • Used to treat shelf-stable boxed juices and milk, as well has single-serving containers of half-cream in restaurants
    • Destroys all microorganisms that can grow under normal storage conditions
  22. Pressurized steam
    • also called autoclaving
    • Typical treatment is 121° C/15 psi for 15 min or longer
    • A process that destroys endospores
    • *Widely used to sterilize microbiological media, lab glassware, surgical instruments, and other items that steam can penetrate.
    • Canning process renders foods commercially sterile
    • Tape that turns black at high temp is attached to signal the item was treated
  23. commercially sterile
    • refers to canned foods, meaning that the endospores of some thermophiles may survive
    • Usually not a concern, however, as they grow only in temps well above normal storage ranges
  24. Dry Heat
    • Not as effective as moist heat in killing microbes, and therefore requires longer times and higher temps
    • Includes:
    • Incineration
    • Dry heat ovens
  25. Incineration
    • Burns cell components to ashes
    • Flaming of wire inoculating loops
    • Also used to destroy medical wastes and contaminated animal carcasses
  26. Dry heat ovens
    • Destroys cell components and denatures proteins
    • Less efficient than moist heat, requiring longer times and higher temps
    • Lab glassware is sterilized by heating at 160° to 170° for 2-3 hours.
    • Powders, oils, and other dry materials are also sterilized in ovens
  27. Filtration
    • filter retains microbes while letting the suspending fluid or air pass through small holes
    • Includes filtration of fluids and air
  28. Filtration of fluids
    • Various pore sizes are available; 0.2 μm is commonly used to remove bacteria
    • Used for beer and wine, and to sterilize some heat-sensitive meds
  29. Microfilters
    • Also called membrane filters
    • paper thin, have microscopic pores that allow liquid to flow through while trapping particles too large to pass
  30. Depth filters
    • trap material within thick porous filtration material such as cellulose fibers
    • Have complex passages that retain microorganisms while letting the suspending fluid pass through small holes
  31. Filtration of air
    • HEPA filters are used to remove microbes that have a diameter of 0.3 μm or greater.
    • Used in biological safety cabinets, specialized hospital rooms, and airplanes.
  32. HEPA filters
    • High-efficiency particulate air filter
    • remove nearly all airborne particles 0.3 μm or larger
    • Used to keep microbes out of specialized hospital rooms designed for pts with extremely susceptible to infection
  33. Electromagnetic radiation
    • Includes radio waves, microwaves, visible and UV light waves, Xrays and gamma rays
    • Form of energy that travels in waves and has no mass
    • Amt of energy is related to wavelength, with is distance from crest to crest fo wave
    • Wavelength is proportional to frequency, the number of waves per sec
    • Radiation that has short waves, and therefore high frequency, has more energy than that which has long waves and low frequency
  34. Radiation
    • Type of cell damage depends on the wave length of the radiation
    • Includes:
    • ionizing and ultraviolet radiation
  35. Ionizing radiation
    • Has enough energy to remove electrons from atoms
    • This harms cells directly by destroying DNA and damaging cytoplasmic membranes
    • Reacts with O2 to product ROS (reactive  oxygen species) that damages other cell components
    • Bacterial endospores are among most radiation-resistant while Gram-neg bacteria (Ex: Salmonella & Pseudomonas) are most susceptible
    • Items can be sterilized even after packaging
    • Used to sterilize heat-sensitive materials including med equip, disposable surgical supplies, and drugs such as penicillin
    • Also used to destroy microbes in spices, herbs, and approved types of produce and meats
  36. Ultraviolet radiation
    • In wavelengths of approx 220 to 300 nm destroys microbes by damaging DNA
    • Actively multiplying most easily killed, whereas bacterial endospores are most UV resistant
    • Penetrates poorly. Even thin film of grease on UV bulb can make it less effective
    • Used to destroy microbes in the air and drinking water, and to disinfect surfaces
  37. Microwaves
    • Don't affect microorganisms directly, but heat they generate can be lethal
    • *Remember, however, that microwave ovens often heat foods unevenly, so even heat-sensitive cells can sometimes survive the process
  38. High pressure
    • Treatments of 130,000 psi are thought to denature proteins and alter the permeability of the cell
    • Products retain color and flavor
    • Used to extend the shelf life of certain commercial food products such as guacamole
  39. Groups for germicides according to potency:
    • Sterilants
    • High-level disinfectants
    • Intermediate-level disinfectants
    • Low-level disinfectants
  40. Sterilants
    • Can destroy all microorganisms, including endospores and viruses
    • Also called sporicides
    • Destruction of endospores usually requires 6-10 hr tx
    • Used to trx heat-sensitive critical instruments such as scalpels
  41. High-level disinfectants
    • Destroy all viruses and vegetative microorganisms, but do not reliably kill endospores
    • Most are simply sterilants used for short time periods, not long enuf to ensure endospore destruction
    • Used to treat semicritical instruments such as GI endoscopes
  42. Intermediate-level disinfectants
    • Destroy all vegetative bacteria including mycobacteria, fungi, and most, but not all, viruses
    • Do not kill endospores even with prolonged exposure
    • This group is used to disinfect non-critical instruments such as stethoscopes
  43. Low-level disinfectants
    • Destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses
    • Do not kill endospores, nor do they always kill naked viruses
    • Intermediate and low level also called general purpose disinfectants
    • In hospitals, used for disinfecting furniture, floors and walls
  44. Alcohols
    • Chemical used as germicide
    • (Ethanol and isopropanol)
    • Easy to obtain and inexpensive
    • Rapid evaporation limits their contact time
    • Aqueous solutions of 60-80% are used as antiseptic to clean skin in preparation for procedures that break intact skin, and disinfectants for treating instruments
    • Quickly kill vegetative bacteria and fungi
    • Do not destroy bacterial endospores and some nakes viruses
    • Denatures essential proteins
  45. Aldehydes
    • Chemical used as germicide
    • Capable of destroying microorganisms and viruses by inactivating proteins and nucliec acids
    • *immersion in 2% solution for 10-12 hrs kills all microbes, including endospores and viruses
    • Irritating to the respiratory tract, skin, and eyes
    • Glutaraldehyde and orthophthalaldehyde are used to sterilize med instruments
    • Formalin is used in vaccine production and to preserve biological specimens
  46. Biguanides
    • Chemical used as germicide
    • (chlorhexidine)
    • Relatively low toxicity
    • Destroys a wide range of microbes, adheres to and persists on skin and mucous membranes
    • Widely used as an antiseptic in soaps and lotions, and is often impregnated into catheters and surgical mesh, used in mouthwashes
  47. Ethylene Oxide gas
    • Chemical used as germicide
    • easily penetrates hard-to-reach places and fabrics and does not damage moisture-sensitive material
    • It is toxic, explosive and may be carcinogenic
    • Commonly used to sterilize med devices
    • Destroys all microbes, including endospores and viruses, by reacting with proteins
  48. Halogens
    • Chemical used as germicide
    • (chlorine and iodine)
    • Chlorine solutions are inexpensive and readily available; however, organic compounds and other impurities neutralize the activity. 
    • Some forms of chlorine may react with organic compounds to form toxic chlorinated products
    • Widely used to disinfect inanimate objects, surfaces, drinking water, and wastewater.
    • Iodine is more expensive and DOES NOT readily kill endospores.
    • Tincture (Iodine mixed with alcohol) of iodine and iodophors can be used as disinfectants or antiseptics
    • *For unknown reasons, Pseudomonas species survive in concentrated stock solutions of idophores
  49. Metals (silver)
    • Chemical used as germicide
    • Most metal compounds are too toxic to be used medially
    • Silver sulfadiazine is used in topical dressings to prevent infection of burns. 
    • Silver nitrate drops can be used to prevent eye infections in newborns
    • Some metal compounds are used to prevent microbial growth in industrial processes
  50. Ozone
    • Chemical used as germicide
    • Unstable form of O2 readily breaks down to an ineffective form
    • Used as alternate to disinfect drinking water and wastewater
  51. Peroxygens
    • Chemicals used as germicide
    • Includes hydrogen peroxide and peracetic acid
    • Readily biodegradable and less toxic than traditional alternatives
    • Effectiveness of hydrogen peroxide as antiseptic is limited due to enzyme catalase breaks it down
    • Hydrogen peroxide used to sterilize containers for aseptically packages juices and milk
    • Peracetic acid is more potent germicide than hydrogen
    • Widely used to disinfect and sterilize med devices
  52. Phenolic compounds
    • Chemicals used as germicide
    • triclosan and hexachlorophene ~ active ingredient in Lysol
    • Wide range of activity, reasonable cost, remains effective in presence of detergents and organic contaminants, leaves an active antimicrobial residue
    • Triclosan used in variety of personal care products including toothpastes, lotions, soaps, etc.
    • Hexachlorophene is highly effective against Staph aureus, but use is limited as it can cause neuro damage
  53. Quaternary Ammonium Compounds
    • Chemical used as germicide
    • Benzalkonium Chloride and Cetylpyridinium
    • Non-toxic enuf to be used on food preparation surfaces.
    • Inactivated by anionic soaps and detergents
    • Widely used to disinfect inanimate objects and to preserve non-food substances
  54. As salt and sugar are used as preservatives, what food-poisoning bacterium can grow in relatively high-salt conditions?
    Staph aureus
  55. Lyophilization
    • freeze-drying
    • widely used for preserving foods
    • when water is added, it reconstitutes
Card Set
Micro ch 5
micro ch 5