Lesson 13 Flashcards
-The goal controlling microorganisms is twofold what are this?
(a) to destroy pathogens and prevent their transmission
(b) to reduce or eliminate microorganisms responsible for the contamination of water, food, and other substances
-microorganism are controlled by what?
Physical agents
Chemical agents
: a process by which an article, surface, or medium is freed of all living microorganisms either in the vegetative or in the spore state
Sterilization
-any material that has been subjected to the above process.
sterile
-: a chemical agent that is used to perform sterilization because of their ability to destroy spores.
Sterilants
-: also called a microbicide, is any chemical agent that kills pathogenic microorganisms either on inanimate (nonliving) materials or on living tissue but not resistant microbial cells.
Germicide
the use of a chemical agent that destroys or removes all pathogenic organisms or organisms capable of giving rise to infection or its harmful products (toxin) thus destroys vegetative pathogens but not bacterial endospores. Used only on inanimate objects because they can be toxic to human and other animal tissue,when used in higher concentrations.
Disinfection
. -: is defined as the growth of microorganisms in the body or the presence of microbial toxins in blood and other tissues
Sepsis
.-: refers to any practice that prevents the entry of infectious agents intosterile tissues and thus prevents infection.
Asepsis
-: are chemical agents applied directly to the exposed body surfaces(e.g., skin and mucous membranes), wounds, and surgical incisions to destroy orinhibit vegetative pathogens.
Antiseptic
-: is any cleansing technique that mechanically removes
microorganisms (along with food debris) to reduce the level of contaminants.
Sanitization
-: a compound (e.g., soap or detergent) that is used to perform sanitization. Air sanitization with ultraviolet lamps reduces airborne microbes in hospital rooms, veterinary clinics, and laboratory installations.
Sanitizer
reduces airborne microbes in hospital rooms, veterinary clinics, and laboratory installations.
Air sanitization with ultraviolet lamps
-a process usually involves scrubbing the skin or immersing it in chemicals, or both. It also emulsifies oils that lie on the outer cutaneous layer and mechanically removes potential pathogens from the outer layers of the skin
Degerming/antiseptis
-Methods of controlling microorganisms
Sterilization
Disinfection
Antimicrobials
Physical methods of sterilization
Sunlight
Heat
Filtration
Radiations
Sonication
-a natural method of sterilization of water in tanks, rivers, and lakes. has an active germicidal effect due to its content of ultraviolet and heat rays
sunlight
-one of the most dependable method of sterilization.
Heat
- higher temperatures (exceeding the maximum) are what ?
,
microbicidal
- lower temperatures (below the minimum) tend to have what?
inhibitory or microbiostatic effects.
-kills microorganisms by denaturation and coagulation of proteins
Moist heat sterilization
-temperature range in moist heat sterilization
-
60-135 degree Celsius
is a technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquid’s flavor and food value.
Pasteurization
This method is extensively used for sterilization of milk and other fresh beverages, such as fruit juices, beer, and wine which are easily contaminated during collection and processing.
Pasteurization
-product is exposed to heat at 72°C for 15–20 seconds followed by a sudden cooling to 13°C or lower
Flash method
- product is exposed to a temperature of 63°C for 30 minutes followed by cooling to 13°C or lower, but not less than 6°C).
holder method
inactivates most viruses and destroys the vegetative stages of 97–99% of bacteria and fungi, it does not kill endospores or thermoduric species (mostly nonpathogenic lactobacilli, micrococci, and yeasts)
Pasteurization
-Simple boiling of water for 10–30 minutes kills most of the vegetative forms of bacteria but not bacterial spores thus only for disinfection.
Boiling
: substances are exposed to steam at atmospheric pressure for 90 minutes during which most vegetative forms of the bacteria except for the thermophiles are killed by the moist heat.
Steam sterilizer at 100°C
-Certain heat-labile substances (e.g., serum, sugar, egg, etc.) that cannot withstand the high temperature of the autoclave
Intermittent sterilization or tyndallization
-Certain heat-labile substances (e.g., serum, sugar, egg, etc.) that cannot withstand the high temperature of the autoclave
Intermittent sterilization or tyndallization
is used most often to sterilize heat-sensitive culture media, such as those containing sera and some canned foods
Intermittent sterilization
- is carried out over a period of 3 days and
requires a chamber to hold the materials and a reservoir for boiling water.
Tyndallization
-makes use of air with a low moisture content that has been heated by a flame or electric heating coil.
Sterilization by dry heat
- In practice, the temperature of dry heat ranges from what?
160°C to several thousand degrees Celsius.
-kills microorganisms by protein denaturation, oxidative damage, and the toxic effect of increased level of electrolytes.
The dry heat.
- is an excellent method for safely destroying
infective materials by burning them to ashes.
Incineration
- is electrically heated and is fitted with a fan to ensure adequate and even distribution of hot air in the chamber. It is also fitted with a thermostat that ensures circulation of hot air of desired temperature in the chamber.
hot-air oven
- is electrically heated and is fitted with a fan to ensure adequate and even distribution of hot air in the chamber. It is also fitted with a thermostat that ensures circulation of hot air of desired temperature in the chamber.
hot-air oven
-remove contaminating microorganisms from solutions rather than directly destroying them.
Filtration
-The filters are of two types:
(a) depth filters; ex candle filter, asbestos filter or sintered glass filters, and
(b) membrane filters; ex, cellulose acetate,cellulose nitrate, polycarbonate,polyvinylidene fluoride, or other synthetic materials made of membrane filters.
- is an excellent sterilizing agent with very high penetrating power. These radiations penetrate deep into objects
and destroy bacterial endospores and vegetative cells, both prokaryotic and eukaryotic but not that effective against viruses.
Ionizing radiation
- usually kills Escherichia coli O157:H7, Staphylococcus aureus, Campylobacter jejuni, and other pathogens.
Irradiation
- from a cobalt-60 source is used for sterilization of antibiotics, hormones, sutures, catheters, animal feeds, metal foils, and plastic disposables, such as syringes, meat and other food items.
Gamma radiation
his method is commonly referred to as “cold sterilization.”
Radiation
-Use of high-frequency sound (sonic) waves beyond the sensitivity of the human ear are known to disrupt cell.
Sonication
-also forcefully dislodges foreign matter from objects.
Sonication
- (up to 80°C) also appears to contribute to the antimicrobial action.
Heat generated by the sonic waves
- are most sensitive to ultrasonic vibrations,
Gram-negative rods
, - are resistant to the sonic wave sterilization
Gram-positive cocci
fungal spores, and bacterial spores
-The process of inactivating microorganisms by direct exposure to chemical or physical agents.
DISINFECTION
-are products or biocides that destroy or inhibit the growth ofmicroorganisms on inanimate objects or surfaces.
Disinfectants
- can be sporistatic but are not necessarily sporicidal.
Disinfectants
- are biocides or products that destroy or inhibit the growth of microorganisms in or on living tissue.
Antiseptics
-Factors Influencing Activity of Disinfectants
temperature
Type of microorganisms
Physiological state of the cells
Environment
most widely used antiseptics and disinfectants in
laboratories and hospitals worldwide. They are bactericidal or bacteriostatic and some are fungicidal also. They act by denaturing proteins and disrupting cell membranes. They are effective in the presence of organic material and remain active on surfaces long after application.
Phenolics compound
- (is effective against vegetative forms of bacteria but not suitable for application to skin or mucous membrane),
Phenol
are more germicidal and less poisonous than phenol but
corrosive to living tissues. They are used for cleaning floors (1% solution), for disinfection of surgical instruments, and for disinfection of contaminated objects.
Cresol
- is a solution of cresols in soap
Lysol
- (like hexachlorophene and chlorhexidine are highly effective against both Grampositive and Gram-negative bacteria.
Halogenated diphenyl compounds
- They are used as skin antiseptics and for
the cleaning of wound surfaces because once
applied it persists on the skin and reduces growth of skin bacteria for longerperiods. However, it can cause brain damage and is now used in hospital nurseries only after a staphylococcal outbreak)
-
hexachlorophene
are fluorine, bromine, chlorine, and iodine—a group of
nonmetallic elements that commonly occur in minerals, sea water, and salts.
Halogens
- kills not only bacterial cells and endospores but also fungi and viruses.
Chlorine
-safe Chlorination concentration
0.6–1.0 part of chlorine per million parts of water makes water potable
-is ineffective at an alkaline pH, less effective in the presence of excess organic matter, and relatively unstable, if exposed to light.
Chlorine
- rapidly penetrates the cells of microorganisms, where it apparently disturbs a variety of metabolic functions by interfering with the hydrogen and disulfide bonds of
proteins (similar to chlorine). But not adversely affected by organic matter and pH.
iodine
- The two primary iodine preparations
free iodine in solution
iodophors (betadine)
-most widely used disinfectants and antiseptics effective at a concentration of 60–70% in water. They are bactericidal and fungicidal but not sporicidal or virucidal.
Alcohol
- are the two most popular alcohol germicides. They act by denaturing bacterial proteins and possibly by dissolving membrane lipids. They are used as skin antiseptics.
Ethyl alcohol and isopropyl alcohol
- is effective against fungal spores.
Methyl alcohol
-are highly reactive molecules that combine with nucleic and alkylating molecules; sporicidal and can be used as chemical sterilants.
Aldehyde
- that is usually dissolved in water or alcohol before use against bacteria, spores and viruses.
Formaldehyde
- is 40% aldehyde in aqueous solution.
Formalin solution
-uses of formalin solution
preserve fresh tissue specimens
destroy anthrax spores in hair and wool
prepare toxoids from toxins
sterilize bacterial vaccine
kill bacterial cultures and suspensions.
-used for sterilization of large volume of heat-sensitive disposable items and also instruments.
Gases
- are frequently used gaseous agents.
Ethylene oxide
Formaldehyde gas
betapropiolactone
-: such as detergents are the substances that alter
energy relationship at interfaces producing a reduction in surface tension.
Surface active agents
- are organic molecules that serve as wetting agents and emulsifiers because they have both polar hydrophilic and nonpolar hydrophobic ends thus are very effective cleansing agents
.
Detergents
-They are different from soaps, which are derived from fats. Four types:
(i) Cationic surface active agents ex: quaternary
ammonium compounds,
(ii) Anionic surface active agents, ex: soap made from
saturated or unsaturated fatty acids,
(iii) Nonionic surface active agents (noteffective),
(iv) Amphoteric or ampholytic compounds or Tego compounds
This group includes halogens, hydrogen peroxide, potassium permanganate, and sodium perborate. They are good disinfectants and antiseptics but are less effective in the presence of organic matter.
Oxidative agents
-used extensively as skin and wound antiseptics include (a) acridine dyes and (b) aniline dyes both more active against Gram positive bacteria
Dyes
-Soluble salts of mercury, silver, copper, arsenic, and other.
have antibacterial activity, both bactericidal and bacteriostatic. They combine with proteins, often with their sulfhydryl groups and inactivate them or may also precipitate cell proteins.
Heavy metals
- (such as sulfuric acid, nitric acid, hydrochloric acid, and benzoic acid
Acids
- (like potassium and sodium hydroxide and
ammonium hydroxide) are germicidal in nature.
alkalis
They kill microorganisms by hydrolysis and altering the pH of the medium.
Acids and alkalis
