Chapter 4 Flashcards
Killing or removal of ALL viable organisms in an object or habitat
Sterilization
Killing, inhibition or removal of microorganisms that may cause disease
Disinfection
Agents used to carry out disinfection and are normally used only on inanimate objects
Disinfectants
Reduction of microbial population to levels considered safe by public health standards
Sanitization
Prevention of infection or sepsis in living tissue using chemicals
Antisepsis
Agents used to carry out antisepsis but generally not as toxic as disinfectants; can be used on living tissue
Antiseptics
Introduced use of phenol (carbolic acid) during surgeries and for wound dressings
Lister
Microbial Control
Inhibition of growth
Destruction of the organism
Why do we control microorganisms
To prevent spoilage of valuable substances
To prevent infection
To prevent contamination of cultures, person, and environment
Agents used in microbial control
Physical agents
Chemical agents
Physical agents
Heat Low temperature Filtration Desiccation Increased osmotic pressure Radiation
Examples of moist heat
Boiling or flowing steam
Pasteurization
Steam under pressure
Tyndallization
Kills vegetative cells and eukaryotic spores within 10 minutes
Boiling or flowing steam
Process that uses brief exposure and high temperature to reduce microbial population and eliminate human pathogens
Pasteurization
Basis of pasteurization
Coxialla burnettii
LTH in pastuerization
62.8C , 30 minutes
HTST in pasteurization
72C , 15 seconds
UHT in pastuerization
140C to 150C , 1-2secs
Uses autoclave or pressure cooker
121C , 15 mins
Steam under pressure
Basis for steam under pressure
Bacillus stearothermophilus
3 successive days
90C to 100C for 30-60 mins
Incubation at 37C in between days
Tyndallization
Another name for Tyndallization
Fractional steam sterilization
Intermittent sterilization
Examples of dry heat
Direct flame
Hot air
Uses bunsen burner or alcohol lamp
Direct flame
Another name for direct flame
Incineration
Uses mechanical convection oven
170C to 180C for 1 hour
Hot air
Limits growth due to decreased rate of cell reactions
Low temperature
Temp at 4C
Refrigeration
Temp at 0C to -95C
Freezing or deep-freezing
Exclusion of microorganisms
For heat-sensitive materials
Filtration
Removes 99.97% micrometer particles
HEPA filter
Microbiostasis
- drying
- freeze-drying
Desiccation
Microbiostasis
Increase solute concentration
(by adding sugar, salt)
Increased osmotic pressure
Types of radiation
Ionizing radiation
Non-ionizing radiation
Results in DNA destruction
Cause atoms to lose electrons or ionize
Excellent sterilizing agent
Ionizing radiation
Example of ionizing radiation
X-rays
Gamma rays
Formation of thymine dimers
Surface sterilization only
Non-ionizing radiation
Non-ionizing radiation is most lethal at ___ which results to ____
260nm
DNA damage
Chemicals that kill microorganisms or prevent growth or prevent growth
Antimicrobial agents
Substances that kill organisms
-cide
Substances that prevent growth of organisms
-static
Examples of chemical agents
Germicide Bactericide Fungicide Algicide Fungistat Bacteriostat
Disruption of plasma membrane
Protein denaturation
Inactivation of enzymes
Phenols
Phenolics
Commonly used in soaps, shampoos, depdorants, etc.
Phenolic compounds
- triclosan/triclocarbon, hexachlorophene
Denature proteins
Dissolve membrane lipids
Alcohols
- ethanol and isopropanol
Oxidation of cell constituents
Also inhibit protein function
Halogens
- chlorine, iodine
Denatures enzymes and other essential proteins
Heavy metals
- silver, copper, mercury
Prevents ophthalmic gonorrhea
1% silver nitrate
Used on burns
Silver sulfadiazine
Algicide
Copper sulfate
Disinfects skin mucous membrane
Merthiolate
Mechanical removal or microorganisms
Surfactants
- soaps and acid anionic detergents
Disrupts plasma membrane and denature protein
Surfactants
- cationic detergents and quaternary ammonium compounds
Used in food and cosmetics
Organic acids
- sorbic acid, propionic acid, etc.
Protein denaturation
Used on heat-sensitive items
Rapidly penetrate packing materials
Microbicidal and sporicidal
Sterilizing Gases
- ethylene oxide
Protein inactivation
Chemical sterilants
Aldehydes
- formalin, glutaraldehyde
Oxidation of cell components
Oxidizing agents
- hydrogen peroxide
Conditions influencing effectiveness of antimicrobial agent activity
Population size Population composition Concentration or intensity of product Duration of exposure Temperature Local environment
Points to remember
Few chemical agents achieve sterility
Spectrum of susceptibility of microorganisms
Factors affecting growth
Temperature Nutrients Moisture Aeration pH
Phases of microbial growth
Lag phase
Log phase
Stationary phase
Death phase
Adaptation phase
Occurs upon initial transfer
No increase in cell mass/number
Synthesis of protoplasm
Lag phase
Cells are dividing steadily at a constant rate
Growth rate is at its maximum
Cells are mostly uniform
Log phase
Growth rate tapers off
- exhaustion of nutrients
- accumulation of waste
Growth = Death
Stationary phase
Death rate > growth rate
Decline in the # of viable cells
Nutrient depletion
Further accumulation of wastes
Death phase
Reproduction
Multicellular
- spores
Unicellular
- binary fission
Measurement of Growth
Standard Plate Growth
Direct Count
Turbidimetric Method
Most common method used
Usually indirectly done through serial dilution and plating
Standard plate count
Advantage and Disadvantage of SPC
A: can determine # of living cells
D: underestimation of cell population
Both viable and non-viable cells are counted
Utilizes counting chamber microscope
Direct count
Indirectly measures cell mass (the more turbid; the higher the cell mass)
Utilizes a spectrophotometer
Turbidimetric method
