microbio session 2

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Author:
nhi
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64526
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microbio session 2
Updated:
2011-02-06 18:34:35
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Microbiology
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Sterilization techniques
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  1. What is commensalism?
    Commensalism: 1 benefits and the other is unaffected
  2. What is symbiosis?
    Symbiosis: stable relationship
  3. What is ammensalism?
    Ammensalism: 1 injured, other one is unaffected (2 types of bugs in mouth: 1 bacteria produce Antibiotic and 1 is harm)
  4. What is latency?
    infection that is dormant within the host (TB lives inside macrophage laying dormant, HIV has latent phase) You can still infect others when you are in latent phase.
  5. What is a parasite?
    Parasite: host is damage in symbiosis gone bad.
  6. What is strict and opportunistic pathogen?
    Opportunistic pathogen: One that will cause disease in the right time and place. Any bacteria can cause disease if its in the right place at the right time.

    • Strict pathogen: not flora EVER.
    • (ex. M. tuberculosis)
  7. What is endogenous and exogenous disease?
    Endogenous disease: disease is produced by organisms in the person's own microbial flora that spread to inappropriate body sites

    Exogenous disease: diseases that arise when a person is exposed to organisms from external sources
  8. What is colonization?
    colonization: long term symbiotic disease
  9. Identify areas of the human body that should be free of microbes.
    Blood, brain, organs, bladder, urine
  10. Describe the flora of the skin and the defenses that prevent infections.
    Skin: keratin - slightly acidic
  11. Describe the flora of the
    eye as well as the defenses found there.
    Eye: tears that wash and flush with enzymes (lysozymes, staph from skin of eye)
  12. Describe the flora and defenses in the respiratory
    Respiratory tract: mucous prevent adherence, cilia that beats the things up, enzymes, IgA, macrophages that lining the area, the deeper you go the lesser the flora, many health care have drug resistant bacteria in their
  13. List the defenses and the flora found in the GI
    GI tract: 1 gram of feces = 1011 bacteria, acids in stomach that protect, secretory IgA, BUGS. GI tract can seriously disrupt by antibiotics.
  14. Which gender is prone to urinary tract infections? Why?
    Women are more likely to get urinary tract infections because urethra is shorter.
  15. Describe the flora of the brain.
    None! Meningitis if bacteria or virus get in there.
  16. What is virulence?
    How infective or harmful the organism is
  17. What is LD50?
    Measure of virulence.

    Of a bug, how many bacteria cells are needed to kill ½ animal in a study/ test group.

    Low LD50 (more virulent the bacteria) or high LD50
  18. What is attenuation?
    • make an organism less virulent. We attenuate organisms to make vaccines. Live organism but less dangerous.
    • Ex. BCG: M. tuberculosis
  19. Describe several virulence factors as they relate to adherence, invasion and colonization.
    • Bacteria become more virulent if they:
    • 1. Stick: Fimbria, pili, glycocalyx (capsule),
    • 2. Invade: Make enzymes to break down your
    • 3. Colonize and create biofilm (stuck and work together)
  20. what is exotoxin?
    secreted toxins that damage your

    • 1. Bacteria secrete enzyme to break down stuff so they can take in the stuff as food
    • 2. Hemolysins break down red blood cells
    • RBC. Allow break down of clot
    • 3. A-B toxins: “A” subunit goes into your
    • cell and alters translationa. Potent in GI tract
    • 4. Superantigens: activates about 20% T
    • cell at the same
    • time nonspecifically.
  21. what are endotoxins?
    • not secreted, part of bacterial cell, often part of cell
    • 1. Ex. LPS. Gram – cell wall, fever
  22. what are enterotoxins?
    • associated with food poisoning
    • stable to heating at 100 C for 30 minutes resistant to hydrolysis by gastric and jejunal enzymesproduced
    • 30-50% of all S. aureus strains
  23. What is the significance of a pathogenicity island?
    Virulence factors: genes can be grouped pathogenicity island: plasmid or main chromosomegenes for some virulence mechanisms are grouped into thisthey are in control of a single promoter to allow their expression under appropriate conditions
  24. How do bacteria evade your immune system?
    a. Depends on the strain of bacteria

    b. Capsules

    c. Enzymes inactivate phagocytes

    d. Salmonella: change protein on their coat routinely. Waves of nausea.

    e. Superantigen: you get really sick but it’s not very useful cuz it’s non specific.

    f. Some learn to live inside of phagocytes. Doesn’t get broken down in phagocytes and live in there
  25. Describe a biofilm. Give several examples of biofilms.
    • Colony of bacteria that often has coating with the
    • bacteria at the bottom is very protected.

    i. Endocarditis: biofilm on the heart

    • In water line and instrument: filters and
    • flushing. More than just in body but the environment too.
  26. Differentiate between the three modes of action of antimicrobials (bacteriostatic, bacteriocidal
    and bacteriolytic agents).
    a. Bacteriostatic: it stops division.

    b. Bacteriocidal: kills bacteria

    c. Bacteriolytic: lyses/ breaks down bacteria
  27. Antiseptics
    a. work against infection. Often used outside of body (skin and mouth). Ex. Soap, triclosan, etOH, iodine, mouthwash, peroxide mouthwash (H2O2)

    Not use internally
  28. Disinfectants
    killing most but not all microbesnot given to pt except alcohol on skin does not kill spores (spores for survival/not production) or all viruses not for instrumentsuse for countertop
  29. sterilants?
    kill all microbes even sporesuse autoclave, gas, radiation, filtered (virus can get through this)
  30. Give examples of antiseptics used in your everyday life – describe the mode of action of soap and alcohol.
    • 1. soap: antiseptic [ it's detergent/oi]
    • 2. alcohol: antisept (you)/disinfect (surface)
    • drying lipid
    • denature proteins not sporicide
    • not effective on TB
    • alcohol on open wound is not recommended because creates a crust with bacteria underneath
  31. What are examples of antiseptic agents used in oral health?
    • 1. chlorhexidine
    • 2. fluoride
    • 3. peroxide
    • 4. mouthwash
  32. How does chlorhexidine work?
    • a. disrupts cell membranes
    • Absorbs onto the gum and teeth for residual activity (+)
  33. How does fluoride work?
    a. inhibits enolase (enzyme in glycolysis)
  34. i. Good for application NOT ingestion (ingested fluoride might be good for something else but not for teeth)
  35. How does peroxide work?
    a. oxidizing agent

    i. Damaging to tissue at high concentration

    • ii. Bacteria
    • can’t handle the oxidative stress but acts same way on your tissue
  36. How does mouthwash work?
    Listerine: phenolics denature enzymes and proteins. Remain active in the presence of other organic molecules. Problem: high concentration can be toxic

    Scope: quat Ammonium act as a surfactant. Target lipid membrane. Can be irritating to tissue and can be inactivate by organic.
  37. sterilization?
    use of physical procedures or chemical agents to destroy all microbial forms, including bacterial spores
  38. Sterilization vs. disinfection
    sterilant: agent used to kill all microbes; ex. ethylene oxide

    gasdisinfection: process of eliminating nearly all pathogens, but not all, from surface or inanimate object

    disinfectant: antimicrobial agent used primarily on inaminate objects, too toxic for patient
  39. Benchark organism for intermediate surface disinfection is what?
    M. tuberculosis: more resistant to low level disinfectants than other bacteriaHIV (virus) is relatively easy to kill compared to M. tuberculosis
  40. what are the desirable properties in disinfectants?
    • high germicidal efficacy
    • germicidal activity in presence of dried
    • blood, other organic matter
    • wide antimicrobial spectrum
    • rapid lethal action
    • penetrate well
    • chemical stability
    • low cost, easily available
    • noncorrosive
    • must kill M. tuberculosis, P. aeruginosa, polio virus
  41. What are the classification of strength of disinfectants?
    • Low: used for noncritical instruments/devices, or general cleaning of floors, countertops.
    • Inter: used for semi-critical instruments and when contamination by resilient microbes or endospores is unlikely.
    • high level: necessary for invasive devices that cannot withstand sterilization
  42. Describe the use and mechanism of action for quaternary ammonium (level of disinfectant?)
    • are detergents - amphipathic molecules kill bacteria by disrupting cell membrane through interactions with lipids in lipid bilayer
    • grap + bacteria most susceptible to destruction many viruses and all bacterial spores are resistant
    • some bacteria resistant; mycobacterium and pseudonas
    • low level
  43. Describe the use and mechanism of action for
    hydrogen peroxide (level of disinfectant?)
    • an oxidizing agent use as a disinfectant - kills most bacteria at a concentration from 3-6%
    • sterilant: kills all organisms, including spores, at [10-25%]
    • free hydroxyl radicals formed from H2O2 decomposition. these are the sterilizing agents, oxidize microbes
    • high level
  44. Describe the use and mechanism of action for
    phenol (level of disinfectant?)
    rarely used disinfectant, too caustic original disinfectant used in hospitals, denatures proteins intermediate-level
  45. Describe the use and mechanism of action for
    formaldephyde (level of disinfectant?)
    • alkylating agentformalin - 37% formaldehyde solution in H2O
    • high/intermediate
  46. Describe the use and mechanism of action for
    bleach (level of disinfectant?)
    • active component of hypochlorite (bleach)
    • high-level disinfectant
    • corrode stainless steel
    • need to get stuff off of the instrument before putting them in autoclave
  47. Describe how physical methods of sterilization each work and when each is appropriate.
    • heat: for hospitals and are indicated for most materials (except heat sensitive, consist of toxic, or volatile chemicals)
    • radiation: limitation - direct exposure is required
    • filtration: removing bacteria and fungi from air or from solns. limit - viruses and some small bacteria
  48. Describe how gas methods of sterilization each work and when each is appropriate.
    • ethylene oxide: most common. efficient but limit - flammable, explosive, carcinogenic
    • formaldehyde gas: carcinogenic
    • plasma gas: H2O2 is vaporized, reactive free radicals are produced w/ no toxic byproducts. this might replace ethylene oxidehydrogen peroxide: oxidizing nature
  49. Describe how chemical methods of sterilization each work and when each is appropriate.
    • antiseptics, disinfectants, sterilant
    • speracetic acid: oxidizing agent, excellent activity, end product is non-toxic
    • glutaraldehyde: safety concern
  50. Know the specific mode ofaction and use for heat.
    • baking
    • using for things that might corrode in autoclave
    • way longer than autoclave
  51. Know the specific mode of action and use for ethylene oxide.
    • most common. efficient but limit-flammable, explosive, irreversibly inactivates DNA and proteins by alkylation
    • inactivates DNA more than other chemical sterilants
    • Adv: use at low temp, does not melt, damage, or corrode things, can sterilize in packages
    • Disad: long time, toxic, flammable
  52. Know the specific mode of action and use for 2% gluteraldehyde.
    • alkylates molecules and inhibits function
    • highly lethal to all microbes (including bacterial endospores)
    • used as liquid immersion sterilant
    • adv: most potent category of chemical germicide (liquid), capable of killing spores, use on heat sensitive materials
    • dis: long period , toxic to human
  53. Classify Pasteurization as a sterilant or disinfectant.
    knock down some pathogens but not sterileother microbes reduced in number
  54. What time, temperature and pressure is needed for an autoclave? How can you test to make sure your autoclave is working?
    • a. 121 C, 15-20 minutes, 15 psi
    • b. test through the use of strips of spores, indicator organisms
  55. Identify when radiation and filtration are appropriate methods of sterilization. How does each work?
    • a. UV light: makes thymine dimers Not generally
    • use in real life

    • Damaging to eye and skin. It doesn’t penetrate glass
    • See this mostly in food prep area or research lab
    • b. filtration: useful for heat-sensitive liquids/gases does not remove viruses and bacterial endospores

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