Counting/Measuring & Controlling Microorganisms Flashcards
Explain Plate Count
add measured amount of sample (can be body fluid, tissue, food, H2O, etc) to growth media, then count colonies that form
Explain Membrane Filtration
Filter organisms onto membrane with a grid. Count org in a few grids (requires microscope) and multiply by number of grids
Name the direct method of counting
- Plate Count
- Membrane filtration
Name the indirect counting methods
- Turbidity
- Luceferin
Explain Indirect Methods
Measures some metabolic activity, not numbers
Explain Turbidity
- For use in clear fluids
- Measures cloudiness of sample
- Only works for high concentrations
Explain Luceferin
- Detects presence of bacteria in foods or on surface
- Really only measures ATP
- Really not a count, Just confirming if bacteria is present or not
- This is quality control tool
- Spray luceferin spray on surfaces, contaminated areas will glow when exposed to a UV/Black light
Define: Sterilization
Kills/neutralizes all organisms
Including spores and viruses
Define: Disinfection
Kills vegetative organisms
Does not kill spores
Designed to kill harmful organisms
Define: Pasteurization
use heat to bring bacterial counts down to “acceptable levels”
Kills most pathogens, extends shelf life
Define: Bacteriostatic
doesn’t kill the bacteria just prevents the bacteria from growing, reproducing, and spreading
Define: Bacteriocidal
Kills Bacteria
Define: Antiseptic
Chemical for destroying harmful microbes but safe to use on living body tissue
Example: Listerine Mouthwash
Define: Sanitation
Lower microbe count to “safe public health levels”
Used for glassware, utensils, etc
Name the 2 types of Radiation
- Ionizing
- Non-Ionizing
Explain Ionizing Radiation
high Energy light (x-rays, gamma rays)
Very effective, high penetration, don’t have to heat
Works by Knocking electrons off atoms & than rearranges them
Used to sterilize medical devices, heat sensitive substances (spices)
Will sterilize food, but not well accepted.
Explain Non-ionizing Radiation
Refers to UV light
- Does not penetrate well
- Good for surfaces, water
- Causes DNA damage (Skin Cancer)
Explain Filtration
Useful for liquids and gases
- Membrane filtration
- Example: HEPA air filters
Explain the Chemical Control & it’s properties: Alcohol
- Disinfectant
- Dehydrates proteins & dissolves lipids
- Mildly effective
- Mostly washes organisms away
Explain the Chemical Control & it’s properties: Heavy Metals
– Disinfectant
- Includes Hg (Mercury), Ag (Silver), Cu (copper)
- Binds proteins together, cellularmetabolism is disrupted
- Only mildly effective
- Higher toxicity
- Not very popular anymore (mostly used for waste disposal)
* Silver nitrate (AgNO3) was used as an antiseptic and disinfectant in newborn eyes to prevent Neisserria gonorrhoeae transferal from mother to baby. Irritates eyes. Not as popular anymore
Explain the Chemical Control & it’s properties: Phenolics
- Phenol = first disinfectant used
- Standard for comparing all disinfectants
- Activity is reduced in the presence of organic matter
- Expensive, odiferous, caustic to skin, not used much as an antiseptic
- Example: Old formula Lysol
Explain the Chemical Control & it’s properties: Cresols
- Phenol derivatives
- Disinfectant
- Greater germicidal activity with lower toxicity
- Used as wood preserver
What are the common Phenol derivatives?
- Cresols
- Hexylresorcinol
- Bisphenols
- Chlorhexidine
- Triclosan
Explain the Chemical Control & it’s properties: Hexylresorcinol
- Phenol derivatives
- Disinfectant & Antiseptic
- Reduces surface tension by loosing the bacteria from tissue which allows for greater penetration
- Found in: Mouthwash, topical antiseptics & Throat lozenges