Control - Physical and Chemical Flashcards
What is the definition of sterilization?
Destruction of all living microbes spores and viruses
How do sterile objects become contaminated?
When exposed tp air and surroundings
What is the definition of sanitization?
Reeduction in the number of pathogens or discourages their growth
-not killing them all
What is the most common physical control of microbial growth?
Heat
-temps above the growth range cause proteins and nucleic acids to be destroyed
What is the thermal death point?
The minimum temp at which it dies in a given time period
What is dry heat?
Requires long periods of exposure to high temps
-heat changes microbial proteins and removes water slowly burning the microbe
What is moist heat?
(like boiling water) is faster and effective at a lower temperature than dry heat
-kills microbes by denaturing their proteins
Why is boiling water sometimes not effective in sanitizing?
May not kill all sores or inactivate all viruses
What is pasteurized steam?
Used in an autoclave as a more dependable way to sterilize a variety of objects
What is an prevacuum autoclave?
Decreases cycle time and exposure of sensitive materials for steam
-uses wet heat to reach a higher temp. The steam is pumped in to increase pressure and allows for water to boil at a higher temp
Why are special indicator bacteria used for autoclaves?
Included in the autoclave to yes that it reached proper sterilizing conditions at all points in the chamber
What is the purpose of a flexible tube?
To bend to the pressure in the autoclave, breaking the testable on the inside with the medium for the spore strip to use
What is pasteurization used for?
rHeating it to a high temp then immediately cooling it to reducing bacterial populations in food and drink
- reduces the chances of spoilage and disease
- bacterial spores not affected by pasteurization
Why is filtering effective in sterilizing?
If the substance can not be heat treated, filtering lets water pass but has small enough holes to keep bacteria/virus out
Why is UV light used to control growth?
Causes thymine molecules to link together in DNA
-errors in protein synthesis and impairment of chromosome replication
What are other types of radiation that can sterilize materials?
X-rays and gamma rays both force electrons out of microbial molecules
What are thee 3 preservation methods to slow spoilage by microorganisms in foods?
Drying: removing water necessary for microbes to live
Salting: causes water to diffuse out of organisms by osmosis
Low Temperature: Lowering microbial growth rates at colder temperatures
What does chemical control usually involve?
Disinfection
-chemical agents rarely achieve sterilization but they do disinfect
What are chemical control methods dependent on?
Depend on the object being treated
What are the 3 forms of chemical control?
Antiseptic: kill pathogens on living tissue
Disinfectant: Used on surfaces
De-germing: Removing organisms from an objects surface
What makes a disinfectant/antiseptic useful?
- Kill or slow growth of organism
- Soluble in water or alcohol
- Long shelf life
- Used in dilute form
- Acts in a short time
- Odourless
What is the phenol coefficient?
Sets the chemical phenol as 1.0 when used as a control agent and other chemicals are prepared at dilutions in test tubes which approximate their usage concentration and are compared against dilutions f phenol for ability to kill microbes
-cleaner strength
What is the disk diffusion method?
Examines the effect of different chemical agents against a specific bacterium
How du halogens control microbial growth?
Oxidize proteins
-Ex: Cl and Iodine
How do phenols control microbial growth?
Compounds denatured proteins
how do heavy metals interfere with microbial growth?
Interfere with microbial metabolism
How do alcohols affect microbial growth?
Denatures proteins and disrupts membranes
What do soaps and detergents act as?
Surface active agents
Purpose of soap?
Removes microbes by emulsifying and solubilizing particles on the skin
Purpose of detergents?
Surfactants
-cause cytoplasm leakage
What does hydrogen peroxide do to microbes?
Damages cellular components
-rxn produces O2 which is effective against anaerobic bacteria
What are Aldehydes?
Cause cross linking that inactivates proteins
What are ethylene oxides?
Effective at removing microbes but carcinogenic and explosive
What is chlorine dioxide?
Non toxic and non carcinogenic gas
What are positively charged (cationic) detergents used for?
Sanitize food utensils and surfaces
What are negatively charged detergents (anionic) used for?
Laundry cleaning and household products
What are dyes used for?
Antimicrobial agent
-first used this to kill bacteria
What is the most common dye used for microbial growth?
Crystal violet is used against gram positive bacteria
What are halogens?
Powerful antimicrobial agents
-Chlorine, Iodine, Bromine
