MCB Exam 4

  1. Cyclic amide functional group which binds to enzymes that cross-link NAM subunits, preventing cross-linkage of NAM subunits, weakening bacterial cell wall & lysing the cell
    Beta-lactam ring
  2. How does inhibition of cell wall synthesis affect bacterial growth?
    Prevents bacteria from increasing amt of peptidoglycan but no effect on existing pep layer (so works only on growing cells)
  3. Example of antibiotic that inhibits synthesis of cell wall
    Penicillin, Vancomycin
  4. Part of antibiotic that is changed when bacteria become resistant
    Beta-lactam ring
  5. Why can taking drugs that inhibit bacterial protein synthesis be harmful to humans too?
    The location of protein synthesis is the ribosome, and the size of ribosomes within the mitochondria of proks and euks differ in size, but according to endosymbiotic theory, human mitochondria originated from bacteria. So both the bacterial AND human ribosomes of the mitochondria will be targeted.
  6. Killing all life forms, including endospores
  7. Avoiding contamination by technique
  8. Harsh method of microbial control which is for object use only
  9. Mild method of microbial control which can be used on skin; bacteria are not killed, just slowed
  10. Killing all harmful life forms, not all life forms
  11. Form of drug chemicals for all diseases in general, like Rx for heart probs, not only microbial related
  12. Suffix -stasis/-static
    stopping growth
  13. Suffix -cide/-cidal
  14. Actions of antimicrobial agents (2)
    • Alteration of cell wall and cell membrane
    • Damage proteins and nucleic acids
  15. How damaging cell wall/mem kills microbes (3)
    • Cell wall integrity damaged and can't prevent bursting due to osmotic effects
    • Cytoplasmic membrane cannot control passage of chemicals in/out of cell
    • Damage to viral envelope so can't attach
  16. How damaging proteins/nucleic acids kills microbes
    • Extreme heat or chemicals denature protein by altering 3-D shape, so protein is no longer functional
    • Chemicals, radiation, heat can produce fatal mutants; also affects RNA
  17. Controlling microbes by removing water; microbiostatic
  18. Effects of high temp on microbe
    • Denaturation of proteins
    • Damage cytoplasmic mem and cell wall
    • Damage structure & function of nucleic acids
  19. Lowest temp that kills all cells in broth in 10 min
    Thermal death point
  20. Time to sterilize volume of liquid at set temp
    Thermal death time
  21. Methods of microbial control using moist heat (4)
    • Boiling
    • Autoclaving
    • Pasteurization
    • Ultrahigh-temp sterilization
  22. Method which kills vegetative cells of bacteria and fungi, protozoan tophozoites, & most viruses w/in 10 min
  23. Method which applies pressure to boiling water which prevents steam from escaping
  24. Alternative method which denatures proteins and oxidizes metabolic and structural chemicals, but requires higher temp for longer time than moist heat
    Dry heat
  25. Method of long term preservation of microbial cultures which prevents formation of damaging ice crystals
  26. Method of adding salt or sugar to inhibit growth; water in cell is drawn out & cell desiccates; fungi can survive it better than bacteria
    Osmotic pressure
  27. Ionizing vs Non-Ionizing Raditation
    -Denatures DNA; used for meats, fresh fruits & veggies

    -Causes thymimn dimer by UV light; used for disinfecting air, transparent fluids, object surfaces
  28. Effects of chemical methods of microbial control varies with: (7)
    and is more effective against: (2)
    • Temp
    • Length of exposure
    • Amt of organic matter
    • pH
    • Concentration
    • Age of chemical
    • _
    • Enveloped viruses
    • Vegetative cells of bacteria, fungi, protozoa
  29. Major categories of chemical control
    • Phenols
    • Alcohols
    • Halogens-algaecide used in pools: bromide or copper
    • Oxidizing agents
    • Surfactants
    • Heavy metals
    • Gaseous agents
    • Antimicrobics
  30. What enzyme neutralizes hydrogen peroxide?
  31. Why are oxidizing agents a good way to control microbes?
    Oxygen kills proteins; microbial enzymes are oxidized
  32. Examples of oxidizing agents
    Hydrogen peroxide disinfectant & ozone treatment of drinking water (kills cysts)
  33. Chemical method of control which dislodges bacteria from hands; reduce surface tension of solvents to make them more effective at dissolving solutes
  34. Chemical method of control which is colorless, tasteless, harmless to humans, and antimicrobial & used in medical settings
    Quats = quaternary ammonia compound
  35. How are heavy metals antimicrobial?
    Metal ions alter 3-D shape of protein so no longer functions
  36. What is used on babies to prevent blindness caused by N. gonorrhoeae?
    1% silver nitrate
  37. What metal inhibits algal growth by interfering w/chlorophyll, so it's used in fish & water storage tanks?
  38. 3 basic principles of antimicrobial therapy
    • 1. Selective toxicity
    • 2. Reach site of infection at inhibitory concentrations
    • 3. Penetrate & bind to target
  39. Exploiting differences in structure & metabolism of pathogens and host cells
    Selective toxicity
  40. 5 modes of action of antimicrobials- what is inhibited or damaged in microbial cell
    • 1. Synthesis of cell wall
    • 2. Synthesis of proteins
    • 3. Synthesis of nucleic acids
    • 4. Damage cell membrane
    • 5. Structural Analogues
  41. Example of disruption of cytoplasmic membrane
    Amphotericin B (polyene) attaches to ergosterol in fungal membranes which makes the cell wall leaky
  42. Drug which disrupts cytoplasmic membranes of Gram-negatives; toxic to human kidneys so given as last resort
  43. Drug which binds to particular enzyme involved in a bacterial metoblic pathway
  44. 2 drugs which target viral metabolism
    Amantadine & rimantadine
  45. Example of a structural analog- Growth factor analog structurally related to PABA which inhibits microbial growth by inhibiting folate synthesis
  46. Why are drugs that inhibit bacterial nucleic acid synthesis toxic to human cells also?
    Only slight differences b/w prok & euk DNA
  47. _____ and _____ (2 drugs) act against prok DNA gyrase
    Quinolones, fluoroquinolones
  48. Drug binds to and inhibits action of RNA polymerase during transcription
  49. General term for drugs that prevent attachment by peptide in viruses
    attachment antagonists
  50. What are the 2 general HIV drugs used
    • Reverse Transcriptase Inhibitors: prevents RT enzyme from turning RNA into DNA; ex: AZT
    • Protease Inhibitors: protease cuts DNA, so this is inhibited
  51. Lowest concentration of a substance that inhibits growth of a test organism
    Minimum inhibitory concentration (MIC)
  52. Test which uses antibiotic-impregnated wafers to test whether particular bacteria are susceptible to specific antibiotics
  53. 3 main categories of side effects
    • Toxicity
    • Allergies
    • Disruption of normal microbiota
  54. Organs that are especially susceptible to toxicity
    • Liver: maintains amt of chemicals in body & removes them
    • Kidneys: excrete these chemicals
    • Also, nerves
  55. Resistance by bacteria is acquired 2 ways:
    • New mutations of genes
    • Exchange of R-plamids
  56. Multiple resistance is caused by:
    exchange of R-plasmids
  57. Bacteria that are resistant to many drugs
  58. When bacteria is resistant to one drug, as well as all other drugs that are in the same family
    Cross resistance
  59. Spread of resistant bacteria throughout the community, outside of hospital setting
    Community transfer
  60. 2 diseases that are most problematic b/c of microbial resistance
    • Staph infection
    • TB
  61. When 2 drugs work in combination & complement each other
  62. Ways to reduce resistant microbes (2)
    • Maintain intake of drug long enough for microbe to be killed off completely, not just until symptoms go away
    • Limit use of antimicrobials
  63. Cellular mechanisms of antibacterial resistance (3)
    • Altered target: target site or enzyme become altered
    • Altered uptake: can increase impermeability of cell wall by losing porins, or by pumping drugs out of cell (efflux)
    • Drug inactivation: producing enzymes which inactivate antibacterial
  64. 2 major types of antifungals
    • azoles
    • polyenes
  65. Antifungal which inhibits cell mem synthesis by blocking biosynthesis of ergosterol
  66. Antifungal which affects function of cell membrane by binding to sterols in it, which causes leakage of cellular compenents & cell death
    Polyenes (Amphotericin B)
  67. Who produces antibiotics in nature (antagonism)
    • Streptomyces: bacteria
    • Bacillus: bacteria
    • Penicillium: fungi
Card Set
MCB Exam 4
Controlling Microbial Growth