Microbial growth

• disinfectants def:


  destroying harmful microorganisms (lysol)
• Antiseptics def:


  destroying harmful microorganisms from living tissue (mouth wash)
• Sterilization def:


  removing and destroying all microbial life (surgery rooms)
• Sepsis def:


  bacterial contamination
• Asepsis def:


  absence of contamination
• Biocides def:

  treatment kills microbes
• Bacteriostatic def:


  treatments inhibit microbial and fungal growth
• Biological safety levels


  • Level 1
  • Level 2
  • Level 3
  • Level 4
• Level 1


  Not known to cause disease; wash hands, dispose of gloves properly
• Level 2


  Human diseases of varying severity but with treatments; use PPE (lab coats, gloves, eye protection), warning signs
• Level 3


  Cause serious or potentially lethal disease; personal training and medical surveillance, work conducted in special containment labs, strict decontamination procedures (tuberculosis)
• Level 4


  High risk of life-threatening disease for which there are no vaccines or treatment; stringent decontamination procedures and autoclaving, multiple containment barriers, work is conducted in highly specialized, high-security labs (ebola)
• Different methods that apply dry heat


  Dry heat: kills by oxidation

  -Incineration: burning materials at very high temps.

  -flaming: common in labs
• Different methods that apply moist heat



  Moist heat: denatures enzymes and proteins

  -autoclave: uses steam under pressure to achieve higher temps

  - pasteurization: heating and cooling as liquid circles

  - boiling: kill most bacteria
• Filtration application:


  Passage of liquid and air through a screen-like material

  -used for heat-sensitive materials

  - filters remove microbes
• Phenol:


  Disruption of plasma membrance

  Use: denature enzymes

  -rarely used
• Phenolics:

  Disruption of plasma membrane

  Use: environmental surfaces, instruments, skin, and mucous membranes
• Bisphenols:


  Disruption of plasma membranes

  Use: disinfectants; ex. hand soaps, skin lotions
• Halogens: 


  Iodine: oxidizing cellular components, antiseptic

  Chlorine: disinfectant

  Flourine: toothpaste, mouthwash = strengthen tooth enamel
• Heavy metals:


  Kills microbes by binding to proteins, thus inhibiting enzyme activity

  -toxic to humans and animals in large amounts, health consequences
• Conditions that affect the activity of an antimicrobial agent

  -population size: large x small

  -population composition: microorganisms x sensitivity to microbial agent

  -conc. or high intensity of antimicrobial agent: higher conc. kills faster

  -duration of exposure: longer = more organisms killed

  -temp: high temp increase amount of killing

  -local environment: pH, viscosity, conc. of organic matter
• Method to test the effectiveness of antiseptics and disinfectants

  Disk diffusion (Kirby-Bauer test): Measures zone of inhibition

  Procedure:

  -inoculum of test microorganism is spread evenly onto the surface of an agar plate using a sterile swab

  -paper disks containing diff concentrations of test agent are placed on the agar surface

  -after incubation, the diameter of the zone of inhibition around each disk is measured
• Surfactants def:


  Chemical compounds that lower the surface tension of water: in soaps and detergents, create emulsions in water to lift dirt and microbes