Microbiology - 0405 - Antimicrobial I

  1. Characteristic Growth Pattern in Static closed system
    • Lag phase: getting used to the new environment
    • log/exp growth phase
    • stationary phase
    • death or log decline phase (if no breakdown, turbidity remains the same)
  2. Continuous Culture
    • Chemostat / Bioreactor
    • can grow infinitely
  3. Inoculum
    Introduction of microbes into medium
  4. Measuring Microbial Growth
    • Direct Measurements: Microscopically total count; dilute + plate + colony count
    • Indirect Measurements: turbidity; Metabolic activity
    • Total Counts
    • Viable Counts
  5. Actions of Microbial Control Agents
    • •  Alternation of membrane permeability
    • •  Damage to proteins
    • •  Damage to nucleic acids
  6. Sterilization
    Removal of all microbial life, including endospores
  7. Autoclave
    • Moist heat/Steam sterilization
    • Kills vegetative cells and spores.
    • Good for utensils and liquids.
    • Might affect heat sensitive biological compounds
  8. Moist Heat/Boiling!
    • •  Boiling water kills bacteria in the vegetative stage.
    • •  Used for cooking and canning of food.
    • •  Boiling doesn't sterilize food, but does reduce the number of disease-causing micro-organisms to a level that is not dangerous
  9. Dry Heat/ Oven
    • Samples are placed into a hot air oven for 120 min at 160 C.
    • Kills vegetative cells and spores.
    • Good for heat-stable items, but not liquids.
  10. Dry Heat/Flaming
    done to loops and straight-wires in microbiology labs.
  11. Pasteurization
    • reduces microbial load, reduces spoilage, increases shelf life, and maintains most of the food composition.
    • • 63°C for 30 min.
    • • High-temperature short-time 71°C for 15 sec.
    • • Ultra-high-pasteurization: 140°C for <1 sec.
    • • Thermoduric organisms survive; won't kill spores.
  12. Filtration Sterilization
    • •  Could be used to sterilize heat sensitive liquids and gases.
    • •  0.2um (common size1x0.5; for viruses, use 0.02um)
    • •  HEPA filter- High-Efficiency Particulate Arresting filter (0.3um).
  13. Radiation
    • •  Radiation damages DNA
    • •  Ionizing radiation (X rays, gamma rays)
    • •  Nonionizing radiation (UV)
    • •  Microwaves kill by heat; not very antimicrobial
  14. UV Radiation
    • Causes modification of DNA by cross-linking DNA.
    • Used to decontaminate surfaces and materials that do not absorb light, such as air and water.
  15. Ionizing radiation
    • -X rays
    • -Gamma rays
    • High energy that produces ions and reactive particles, which can alter DNA, lipids, proteins and spores.
    • Used to penetrate solid or light-absorbing materials
  16. Low temperatures and freezing inhibit growth, but
    does not kill microorganisms.
  17. Biocide/Germicide:
    Kills microbes.
  18. Sterilization:
    Removal of all microbial life.
  19. Sanitization:
    Lower microbial counts.
  20. Disinfectants:
    substances that are applied to nonliving objects to remove pathogens.
  21. Antiseptics:
    substances that are applied to living surfaces such as skin to to remove pathogens.
  22. Antibiotic:
    Substance produced by one microorganism that can destroy or inhibit the growth of other microorganisms.
  23. Antibacterial
    a compound or substance that kills or slows down the growth of bacteria.
  24. Bactericidal:
    Substance that can kill bacteria.
  25. Bacteriostatic:
    Capable of inhibiting the growth of a bacteria. some bactericidal sub becomes bacteriostatic at low concentration.
  26. Joseph Lister
    • antiseptic surgery
    • promoted the idea of sterile surgery.
    • Used carbolic acid (phenol) to sterilize surgical instruments and to clean wounds
  27. Chemical Antiseptics and Disinfectants
    • Alkylating agents: Ethylene oxide, aldehyde
    • Heavy metals
    • Alcohols
    • Halogens
    • Phenols and derivatives
    • Oxidants
    • Detergents
  28. Ethylene oxide
    • Used as gas vapor.
    • sterilize heat sensitive equipment and drugs.
    • Efficient but limited use: Flammable, explosive and carcinogenic.
  29. Aldehydes
    • •  Inactivate proteins by cross-linking with functional groups (–NH2, –OH, –COOH, —SH).
    • •  Glutaraldehyde and formaldehyde.
  30. Heavy metals
    • Mercury
    • Silver
    • Zinc
    • Copper
    • Denature proteins and enzymes by binding to reactive groups resulting in their precipitation and inactivation.
    • Mercury containing compound used as antiseptic.
  31. Alcohols
    • Denature proteins and dissolves lipids by acting on cell membranes.
    • Pure alcohol is less effective as it will dehydrate a cell but will not kill it. Rehydration could resume viability.
    • Usually used at 70% concentration (30% water).
    • 60-95%, >=10sec, kills S. pyogenes
  32. Halogens
    • Iodine: Povidone iodine. To clean skin before surgery with soap -> alcohol -> iodine (red).
    • Chlorine: Used in swimming pools, water treatment units, and bleach.
  33. Phenols and derivatives (Phenolics)
    • Phenol: mouth rinses (Listerine), Lysol
    • Triclosan: anti-bacterial soap
    • Disrupt plasma membranes
  34. Oxidants
    • Hydrogen peroxide (H2O2)
    • Kills bacteria at 3-6%.
    • Kills spores at 10-25%.
  35. Detergents - Surface-Active Agents or Surfactants
    • Dissolve membranes.
    • QACs
    • SDS: Most common ingredient in toothpaste.
    • Chlorhexidine: in mouth rinses.
  36. Antimicrobial Agents Selective toxicity
    a drug that kills bacteria without damaging the host: Therapeutic index
  37. First synthetic chemotherapeutic agents w/ Selective toxicity
    • Salvarsan ( compounds “606”) by Paul Ehrlich
    • treat syphilis
    • Arsenic based compound (toxic disrupts ATP production).
    • Difficult and painful to inject.
  38. Growth Factor Analogs
    • synthetic metabolic inhibitors
    • sulfa drugs, isoniazid, and nucleic acid analogs
  39. Sulfa Drugs - Sulfanilamide
    • Gerhard Domagk
    • The first widely used growth factor analogs that specifically inhibit the growth of bacteria
    • analog of a part of the vitamin folic acid (a nucleic acid precursor), blocks folic acid synthesis, inhibits nucleic acid synthesis.
    • Broad spectrum
    • effective on bacteria, which synthesize folic acid, but not humans who obtain folic acid from their diet.
    • Resistant mechanism: Obtain folic acid from the environment/host
  40. Nucleic acid analogs
    • Blocks nucleic acid synthesis.
    • Used to treat viral and fungal infections.
  41. Quinolones and Fluoroquinolones (Ciprofloxacin)
    • Blocks and inhibits DNA gyrase (unwinds DNA) - DNA replication is stopped.
    • Broad-spectrum.
    • Used to treat urinary tract infections, penicillin resistant anthrax, and TB.
  42. Mechanisms of Resistance to Quinolones
    • •  Decrease intracellular quinolone concentration by efflux pumps.
    • •  Plasmid-mediated resistance genes that produce a proteins that can bind to the target DNA gyrase and protect it from drug.
    • •  Mutation in the DNA gyrase that can decrease its binding affinity to quinolones, reducing drugs effectiveness
Card Set
Microbiology - 0405 - Antimicrobial I
Microbiology - 0405 - Antimicrobial I