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 Sterilization: is the destruction of all forms of microbial life w/particular attention to bacterial spores  Disinfection: refers to the destruction.

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Presentation on theme: " Sterilization: is the destruction of all forms of microbial life w/particular attention to bacterial spores  Disinfection: refers to the destruction."— Presentation transcript:


2  Sterilization: is the destruction of all forms of microbial life w/particular attention to bacterial spores  Disinfection: refers to the destruction of pathogenic organisms on an inanimate object.  Antisepsis (Asepsis): refers to the destruction of pathogens on a living object, ex. Skin surface.

3  Germicide: any chemical agent that kills microorganisms.  Bactericide: an agent that destroys bacteria.  Fungicide: an agent that destroys fungi.  Viricide: an agent that destroys viruses.  Bacteriostatic Agent: prevents the further multiplication of bacteria w/o necessarily killing all that are present.

4  Temperature: germicides are more effective @ high temps.  Type of microorganisms: microorganisms vary in susceptibility depending on things like composition of cell wall, the presence of a capsules & the ability to form spores or cysts.  Environment: can affect the activity of a germicide ex. It can form a shield that reacts w/the germicide.

5  Physical methods for controlling the growth of microorganisms can be divided into heat & non- heat methods.  The lowest tempt. where all microorganisms are killed in 10 minutes is the thermal death point.  Thermal Death Time: min. amount of time needed to kill pathogens @ a given tempt.  Decimal Reduction Time: time where 90% of all microorganisms are killed.

6  Dry heat kills microorgansisms by reacting w/& oxidizing their proteins. Examples of dry heat:  Incineration devices like Bunsen burner  Hot Air oven (tempt. Over 170 ̊C for 2 hours = sterilization)

7  Moist heat is used to kill microorganisms in such things as boiling water.  Most microbial growth is killed w/in 2-3 minutes, but 2-3 hours may be required for destruction of bacterial spores.  In moist heat, the microbial proteins undergo denaturation, a process where the 3-d form of the microorganism reverts to a 2-d form & the proteins break down.

8  Autoclave- a high pressure device that superheats steam & requires only 15 minutes to achieve sterilization.  Pasteurization- is used to lower the bacterial content of milk & dairy products, it doesn’t reach sterilization.  Tyndallization (intermittent sterilization)- liquids & other items are heated w/steam for 3 days to kill microorganisms & spores.

9  Filtration- a process where a liquid or gas passes through a series of pores small enough to retain (filter) microorganisms. Often used when heat sensitive materials like vaccines are to be sterilized.  Drying- removes water from cells which causes them to shrivel & die.  Cold temperatures- @ low tempts. Microbial growth slows, however it does not kill. However, @ freezing tempts, kills some microorganisms but not all.

10  Radiation- changes the chemical composition of microorganisms. Ex. Food & other materials subjected to gamma rays or x-rays.  Ultraviolet Light- non-ionizing radiation affects the nucleic acids & DNA of microorganisms which causes cell death.  Microwave – form of radiation that cause H 2 O molecules to vibrate rapidly causing heat that kills some microorganisms.

11  Chemical agents are not intended to cause sterilization. Most just reduce the microbial populations to safe levels.  Criteria for selecting chemical agents (disinfectants or antiseptics) are the concentration of disinfectant to be used, whether the agent is a bactericidal or bacteriostatic, the nature of the material to be treated, whether organic matter will be present, the tempt & pH @ which the chemical agent will be used, & the time available in which the chemical agent will be left in contact w/the surface treated.

12  Phenols are one of the 1 st chemicals used as a disinfectant by Joseph Lister in the 1860’s.  Phenolics useful as antiseptics & disinfectants.  Both cause denaturing of microorganisms’ proteins & enzymes.  Ex. Lysol, & Hibiclens.

13  Iodine: is used as an alcohol & iodine mixture & includes Betadine, & Povidone. It’s used to denature the proteins of microorganisms & inhibit their function.  Chlorine bleach is used to disinfect objects & sanitize glassware.

14  Useful against bacteria & fungi, but it has no effect on spores.  70% Ethyl Alcohol (Ethanol) is the most widely used alcohol.  Isopropyl Alcohol (Rubbing Alcohol) is used as an antiseptic & disinfectant.  Because alcohol evaporates quickly, it leaves no residue on skin prior to injections.

15  Silver: used in the eyes of newborns to guard against infection & to cauterize wounds.  Copper is used to slow the growth of algae in swimming pools, fish tanks, & reservoirs.  Zinc is used in mouthwashes & as an antifungal agent in paints.

16  Soaps & detergents decrease the surface tension b/w microorganisms & surfaces thereby cleansing the surface.  Soaps emulsify the oily film on the body surface carrying oils, debris & microorganisms away.  Dtergents break down the cell membranes of microorganisms

17  Examples  Penicillin- prevents gram positive bacterial from forming. It’s not just 1 antibiotic but an entire family of antibiotics. It includes penicillin F, G, X, ampicillin, amoxicillin, nafcillin, & ticarcillin.  First penicillins came from green mold but now most are man made.


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