Sterilization
The procedure of making some object free of live bacteria or other microorganisms (usually by heat or chemical means)
Disinfection
Treatment to destroy harmful microorganisms
Antisepsis
Disinfection directed at a living tissue
Degerming
Mechanical removal of microbes. Ex: alcohol swab
Sanitization
Reducing the number of microorganisms to a safe level
Bacteriostasis
Stops growth of microbes
Asepsis
Absence of significant contamination
How do microbes go through a pattern of death?
At a steady rate!
What factors would affect a microbial control agents job harder?
Concentration of disinfectant, organic matter, pH, time
How do microbial agents affect the plasma membrane?
The agents target the PM and destroy the lipids/proteins, this makes the cell to leak (growth is stopped)
What happens when microbial agents damage nucleic acids? Proteins?
Because nucleic acids contain the DNA for the cell when damaged the cell can no longer replicate and continue to grow. When the proteins are damaged you lose your synthesizing properties!
Would a chemical control agent that affected PMs affect humans?
Yes, humans have plasma membranes so we would be affected...don't drink bleach.
How does moist heat work?
Moist heat coagulates the proteins (denatures them). This causes the Hydrogen bond to be broken and the cell loses its 3D shape. Ex: frying an egg white...liquid --->solid(amorphous state)
Autoclave
Instrument for sterilization by means moist heat (steam) high under pressure, raises the heat to that above boiling.
How is microbial growth in canned foods prevented?
By heating, it denatures the proteins in the food which render the bacteria harmless.
Filtration
Tiny filters keep microbes from passing through
How do low-temps suppress microbial growth?
Slow the metabolic rates so much that the bacteria cannot reproduce or synthesize toxins
High Pressure
Alters molecular structure of proteins and carbs, this triggers a rapid inactivation of vegetative bacteria
Desiccation
Absence of water in the cell, the cell remains dormant until reintroduced to water. Water is essential to cell growth.
How does osmotic pressure suppress bacterial growth?
By drying out the cell of all its moisture, without moisture the cell cannot grow
How does radiation kill cells?
Radiation ionizes the water in the cells, this creates a harmful toxic oxygen called a hydroxyl radical. These damage the cells DNA.
Effective disinfection depends on what?
The nature of the disinfectant, pH, how easily the disinfectant can get into contact with the bacteria, amount of time needed.
Why would your choice of disinfectant matter when cleaning a vomit and sneeze?
Both of these messes include different types of microbes, with different levels of pH, there are most likely more bacteria in vomit than in sneeze product.
How does a use-dilution test
Uses a small stainless steel cylinder; affected with growth mixed w/water; let dry; dip in agent; incubate to see if any growth.
Disk-diffusion test
This method is used to see what agent is most effective against certain bacteria. A few soaked disks are placed in a petri dish with microbe spores to show the differences in effectiveness.
Phenol
Disrupts the PM, denatures enzymes.
Rarely used
Phenolics
Disrupts PM, denatures enzymes
Used on env. surfaces, instruments, skin, and mucous membranes
Bisphenols
Disrupt PM
Hand soaps and skin lotions
Why does alcohol work on some viruses but not on others?
Alcohol only works on non enveloped viruses.
How are surface-active agents used?
In soaps and detergents.
They decrease surface tension which breaks up the layers of whatever on the skin.
What characteristics make surface-active agents attractive to the dairy industry?
Their ability to react with microbe's plasma membrane because of the (-) charged portion of their molecule.
Why is glutaraldehyde preferred over other chemical disinfectants?
Because it causes less irritation to the skin.
What chemicals are used to sterilize?
Heated hydrogen peroxide and peracetic acid
Why are gram (-) bacteria more resistant to biocide than gram (+) bacteria?
Gram (-) bacteria are more resistant because their porins (located on the outside of the cell) are extremely selective with what molecules they allow through.