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38 Cards in this Set
- Front
- Back
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What are the methods of microbial growth control?
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Methods:
- Physical Agents × Heat × Radiation - Chemical Agents × Gases × Liquids - Mechanical removal × Filtration of: o Air o Liquids |
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What is sterilization?
(Microbial control) |
× Sterilization- destruction of all forms of microbes including endospores (by/*through* steam under pressure or ethylene oxide)
*like how you can steam things or put stuff in hot water to sterilize it, like the rug masters when you steam and heat the carpet* |
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What is commercial sterilization?
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×Commercial Sterilization - streilization of canned food by heat treatment to kill endospores Clostridium botulinum
Not complete sterilization- usually used to kill microbial bad things in canning process of foods |
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What is disinfection?
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×Disinfection- destruction of vegetative cells of pathogenic microorganisms (by chemicals of physical methods)
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What is pasteurization?
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× Pasteurization - application of high temperature (72C) for a short period of time (15 seconds)
Not complete removal of microbes just partial just like in commercial sterilization |
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What is sanitization?
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×Sanitization- Lowering the number of microbes on eating and drinking utensils (by heat of chemical disinfectant)
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What is Decontamination?
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×Decontamination- mechanical removal of microbes from organisms or non-living objects
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Define : Bactericidal (germicial, microbicidal)
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×Bactericidal (germicial, microbicidal)- agent that destroys or kills bacteria (suffix cide=kill) *like suicidal* *kills it*
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What is an agent that inhibits bacterial growth (stasis=to stop) *stops it* ?
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×Bacteriostatic
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What is Antiseptic?
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×Antiseptic- Antimicrobial agent that is sufficently non-toxic to be applied on living tissue *like the thing on my forehead – just something that is non-toxic*
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How to microbes die?
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× Permanent loss of reproductive capabilities *like the psychological thing where women are like I might as well be dead*
× The cell structures become dysfunctional *exactly like menopause- hot flash* *stops working- pointless* × Antimicrobial treatment leads to killing of microbial population at the constant rate *The number of bacteria population goes down when the time is increased when there is a antimicrobial treatment applied |
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What are the factors that affect the death rate of microbes?
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× Time exposure (lower temp can be compensated with longer exposure)
× The number of microbes *if there was one microbe then it’d take a longer time to affect anything* × Microbial characteristics (endospore, vegetative cells) × Agent used *what was used to kill it like if it was through steam and pressure or whatever* × Environmental influences (suspending medium, pH) |
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How do antimicrobial agents work?
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The mode of action of antimicrobial agents *how antimicrobial agents work, how it kills things*
× Plasma membrane- when damaged, cell content leaks into the surrounding medium (image 11.3) - Proteins- enzyme active sites inactivated (image 11.4) - Complete denaturation ( Different shape) - Blocking the active sites × Nucleic Acid (image 11.9) - Ratidation or some chemicals that can lethally damage the DNA or RNA (microbes can no longer replicate) - UV radiation causes formation of dimers between two tymine bases |
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How does heat control microbes?
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× Heat
- Moist heat and dry heat - Mechanism: denaturing the enzymes - Most commonly used method of killing the microbes - Thermal Death Point- the lowest temp at which all the microbes are killed in 10 minutes - Thermal Death Time- the minimal length of time needed to kill all bacteria at given temperature |
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What is moist heat and how does it control microbes?
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- Moist Heat—nonpressurized steam/ slight pressure
× Mechanism: coagulation of proteins × Boiling (100C) for 10 minutes kills vegetative cells of bacteria, viruses, and fungi × Heptatitis virus can survive up to 30 minutes of boiling; some bacterial spores can last more then 20 hours ×Tyndalization - boiling medium for 60 minutes repeatedly for 3 days Tyndalization: Sterlizing media that cannot take extreme pressures and temperature… the spread out method because whatever survived germinates and transformed into vegetative cells between the next day |
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What is an autoclave?
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- Autoclaves - steam under pressure (image 11.5) *does what other stuff does but since it’s higher pressure, it goes a lot quicker*
× Provide high temperature and high pressure (pressure: 1 atm, temperature 121C) × All microbes are killed in 15 minutes × Steam should contact all surfaces when in autoclave × Time is different for larger volumes × Used for sterilization of: - Culture media - Equipment - Biological waste |
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Describe the process of pasteurization.
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Pasteurization
×Original pasteurization: 63C for 30 minutes ×Todays pasteurization- high temperature short-time pasteurization: 72C for 15 seconds or ×Ultra-high-temperature treatment- exposure to 134C for 3 seconds, then rapidly cooled Note: Used for milk. To not change the taste or texture of milk.. or other foods. |
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How does dry heat sterilization work?
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- Dry heat sterilization *since there’s no moisture in there*
× Mechanism: oxidation × Flaming- (ex. inoculating loops) × Hot-air sterilization -( Oven 170C for 2 hours) × What is more efficient: dry heat or wet heat? Duh autoclaves are more efficient then ovens… so wet heat |
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What is Desiccation?
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- In the absence of water microbes cannot grow but can survive *like glycocalyx if it’s better hardened than a slime layer since there’s more protection*
- Bacterial spores can survive for centuries - Survival depends on microbial type and organisms environment (embedded in mucus- better survival) - Mycobaterium tuberculosis- long survival - Neisseria gonorrhoeae- dies after a few hours of air drying |
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What are the effects of low temperature on microbes.
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Effect depends on the microbial type
× Ordinary refridgeration (0-7C)- bacteristatic effect × Psychotrophs grow slowly × Pathogenic bacteria will not grow × Rapid freezing- microbes become dormant × Slow freezing- more harmful--- *freeze and you can damage the structures × Lyophilization- frozen samples (bacterial culture) dried in vacum *best temperature to grow bacteria is average body temperature |
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How does radiation work.
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Radiation
× 1. Ionizing radiation (gamma rays, x-rays) radiation ejects electrons ions are formed × 2. Nonionizing radiation (UV light) |
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What is Ionizing radiation?
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Nonionizing radiation
× UV light, germicidal light- 260 nm—used for disinfection × Mechanism of action - Damage of DNA- formation of thymine dimers - Toxic free radicals are formed × Sterilization of the air (hospital rooms, operating rooms, cafeteria) × Disadvantage - Poor penetration - Harmful for human eyes and skin |
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How does filtration work?
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Filtration (image 11.11)
× Removal of microbes from a solution × Membrane filters (pore size 0.2 or 0.45 µm) |
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How does osmotic pressure affect microbes.
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Osmotic pressure
× High concentration of salt (or sugar) causes the water to leave the cell × Used in preservation of food (high sugar concentration in fruit preserve) |
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The effectiveness of a disinfectant depends on what?
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× Effectiveness of the disinfectant depends on:
- Type of chemical agent - Type of microbes - Concentration of a disinfectant - Time of contact-- the longer you expose the more likely your removing the population - pH of the medium - Temperature |
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What are the two types of disinfectants?
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halogens and phenolics
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What are halogens?
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Types of Disinfectants
× Halogens - Flourine, bromine, chrlorine, and iodine - Iodine is the oldest antiseptic - Iodine tincture- skin disinfection - Chrlorine- gas (Ca- hypochlorite; Na-hyochlorite --- which is bleach) - Mode of action: oxidating agent- alters cellular components - Disinfection of drinking water, swimming pools, and households (bleach) *rather then using chlorine you can use UV lights but its more costly so we don’t |
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What are phenolics?
Chemical control. |
× Phenolics (derivatives of phenol) (image 11.12)
- Used fort time by Lister- carbolic acid - Mechanism of action: damages the plasma membrane, enzyme inactivatoin - Advantage: active even in the presence of organic compounds (*if u have a really filthy surface some disinfectants don’t work but phenolics do) - Hexachlorophene (bisphenol) used in antimicrobial soaps |
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How do alcohols work in controlling microbeS?
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Alcohols
× Ethanol or isopromanol 60%-95% × Kills vegetative cells of bacteria and fungi (not spores and nonenvelope viruses) × Mechanism of action: protein denaturation × Is pure ethanol a better disinfectant than 70% ethanol: no 70% is better |
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How does hydrogen peroxide work in controlling microbes?
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Hydrogen Peroxide
× 3% solution used as an antiseptic × Skin and wound cleansing × Mouthwash × Contact lens × Surgical implants × Endoscopes |
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What are chemicals with surface action?
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Detergents and soaps.
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How do detergents and soaps work?
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× Detergents are polar molecules- surfactants
× Decrease the surface tenstion among molecules and water × Soaps and detergents are not antiseptics- they vreak the oily film on the surface of skin × They have microbicidal power when mixed with quaternery ammonium compounds |
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What are the two heavy metals with germicidal significance?
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× Only mercury and silver have germicidal significance
× Mechanism of action ions combine with sulfhydril groups- protein denaturation × 1% silver nitrate- antiseptic × Copper sulfate- controls algal growth × Can be toxic to humans |
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How is a disinfectant evaluated?
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Evaluation of a disinfectant:
× Filter paper method - Paper discs are soaked in a solution of disinfectant and placed on an agar previously inoculated with a test organism - Observe the inhibition zone around the disk\ |
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What are aldehydes?
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(formadehydes, glutarradehyde)
×Most effective antimicrobials |
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What is formalin?
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Aldehydes (formadehydes, glutarradehyde)
× Most effective antimicrobials × Formalin- used for the preservation of biological specimens - High level disenfectant - Toxic- carsinogenic |
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What is Glutaraldehyde?
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× Glutaraldehyde
- Used for disinfection of hospital instruments - Considered as a sterilant - Mode of action: forms covalent cross links with finctional groups of proteins - Kills bacterial spores (vegetative cells), fungal spores and viruses |
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What are Gaseous Chemosterilizers and how do they control microbes?
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× Ethylene oxide- gas
× Sterilization withiout heat × Mode of action: denaturation of proteins × Advantage: highly penetrating × Disadvantage: toxic, explosive |
