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. What would you like to do?
- To kill
- Ex: Microbiocidal, Bactericidal, Fungicidal
- to stop
- Ex: Microbiostatic
A sterile object that is harboring microorganisms and viruses
Destruction or removal of all forms of microbial life, including endospores
Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food
Destruction of vegetative pathogens. (In lab)
Destruction of vegetative pathogens on living tissue.
Treatment intended to lower microbial counts on eating and drinking utensils to safe public health levels.
PHYSICAL METHODS OF CONTROL
Physical agents for controlling MOS growth are intended to achieve sterilization
- Thermal Death Time (TDT) - the lenght time required to kill a bacterial population at a given temperature.
- Thermal Death Point (TDP) - the minimum temperature required to kill a bacterial population at a given temperature.
- Works by Oxidation
B. Dry Heat
- Hot air oven
- Radiating dry heat for sterilization
- 160 degrees C for 2 hours
- will kill spores
- Glassware, dry powders, etc.
- Works by oxidation, but organics must be removed
C. Moist Heat
- A. Boiling Water- moist heat penetrates faster than dry heat. Works by denaturing proteins, however, it does not kill many spores or many viruses. (will not sterilize)
- B. Steam under pressure- autoclave. This is the most dependable method of sterilization.
- Autoclave 121.5 degrees C for 15 minutes
mild heating, not sterilization
- A mechanical method to remove microorganisms by passing a liquid or air through a filter
- HEPA filter- removes 99% of all particles
- OR, burn units, etc.
- A. Ultravilet UV (radiant energy)
- Works by 2 methods thymine to thymine producing the wrong protein code & by imparing the replication of the chromosome prior to binary fission
- Will not work on spores.
F. Drying or Dessication
- Dry out
- Works by disrupting metabolism
- No water = no chemical organisms
- Bacteriostatic- stops the growth
G. Osmotic Pressure
Plasmolysis- removal of water in a hypertonic solution
H. Low Temperature
- Bacteriostatic (Fridge)
- Retards growth by lowering the metabolic rate of MOS
CHEMICAL METHODS OF CONTROL
Chemical agents rarely achieve sterilization. They destroy the pathogenic organism on or in an object.
- Highly reactive releasing oxygen
- Strong oxidizers which inactivate certain proteins and enzymes and may change cell membrane structure
- Chlorine combines with water to form HYPOCHLOROUS ACID (*active ingredient)
- Sodium hypochlorite- Clorox bleach
- Drinking water, pools, etc
- Effective against a broad spectrum of organisms including most G+ & G- organisms, many viruses, fungi, and protozoa.
- Not sporicidal, not sterilization
- More germicidal than chlorine
- Tincture- a substance dissolved in ethyl alcohol, Antiseptic for wounds
- Iodophor- a complex of iodine and detergents that is used as an antiseptic and disinfectant. An advantage of iodophors is the fact that it releases Iodine over a long period of time and doesn't stain
- Ex: Betadine, used in pre-operative skin prep.
B. Phenol (carbolic acid, phenolics & bisphenols)
- Expensive & odoruous, & harsh to skin
- Phenolics are phenol derivatives that have a germicidal activity and lower toxicity
- Bisphenols- 2 molecules of phenol joined together. Lysol.
- Triclosan-a bisphenol that disrupts cell membranes by blocking the synthesis of lipids. Found in kitchen sponges, utensils, & cutting boards
- Disadvantage, possibility of bacterial species developing resistance to triclosan
- Ethyl alcohol (ethanol) is the preferred alcohol
- Works by protein denaturation & lipid dissolution
- Bactericidal & fungicidal (on things that are not alive)
- Not effective against endospores or non enveloped viruses
- Mode of action is degerming
- Coagulates cytoplasmic proteins forming a layer that microorganisms get under and grow, on skin not good.
C. Soaps & Detergents
- Soap is a chemical compound of fatty acids combined with potassium or sodium hydroxide
- The pH is around 8.0
- Mode of action : mechanical removal
- Soaps are surface active agents called surfctants (degermer)
- Emulsify & dissolve particles clinging to a surface & reduce surface tension
D. Hydrogen Peroxide- Peroxides
- Hydrogen Peroxide reacts with catalase (enzyme in skin cells) to form oxygen &water
- Not a good antiseptic but works on inanimate objects
- H2O2 reacts with catalase= water & oxygen, bubbles, oxygen being liberated.
What would you like to do?
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