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:
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.
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.
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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.