Lecture 7 Flashcards
(34 cards)
What is sterilization?
The process by which all living cells, spores, and cellular entities (ex viruses, viroids, and prions) are either destroyed or removed from an object or habitat
How can sterilization be accomplished?
By incineration, nondestructive heat treatment, certain gases, exposure to ionizing radiation, some liquid chemicals, and filtration.
What is disinfection?
It is the destruction of pathogenic microorganisms by processes that fail to meet the criteria for sterilization.
Bacterial spores, organisms with waxy coats, and some viruses may show considerable resistance to common disinfectants.
Disinfectants are usually used only on inanimate objects
Sanitization is:
closely related to disinfection. The microbial population is reduced to levels that are considered safe by public health standards.
Are used primarily in housekeeping and food preparation contexts
Antisepsis is:
the destruction or inhibition of microorganisms on living tissue
Antiseptics:
are chemical agents applied to tissue (animate) to prevent infection by killing or inhibiting pathogens. They also reduce the total microbial population.
Antiseptics must not cause much harm to the host; they are generally not as toxic as disinfectants
Is the use of chemical agents (antibiotics) to kill or inhibit the growth of microorganisms within the host tissue ( inside human or animal body)
Chemotherapy
Substances that kill microbes often have the suffix ___
-cide
Germicide:
kills pathogens (and many non-pathogens) but not necessarily endospores
Sporicide:
eliminates spores
Chemicals that do not kill, but do prevent growth have the suffix:
-static
-Example: bacteriostatic and fungistatic
What are 3 reasons why sterilization may be used?
-Prevent infection
-Improve surgery or intrusive medical techniques
-Food preservation
What are the physical methods of sterilization involving heat?
-Incineration
-Dry heat
-Moist heat
-Pasteurization
-Tydallization
-Autoclave
-Low temperature
How does incineration work?
Expose the surface of the object to direct flame. Ex: flaming wire loops, knife, blade, or needle ( in the microbio lab or for emergency sterilization)
How does dry heat work?
Using oven heat at 160C for 2 hours
Kill vegetative bacteria and spores (sterilization)
Is applicable for metals, glassware and some heat resistant oils and waxes
How does moist heat work?
Boiling or hot water or steam
Reactive water molecules denature proteins in microbes
Kill most of the vegetative bacteria (disinfection)
Bacterial spores can resist boiling for prolonged periods
How does pasteurization work?
Is the use of heat at a temperature sufficient to kill pathogenic organisms in liquids such as milk, beer, or other food products.
Pasteurization does not sterilize, but it drastically slows spoilage by reducing the level of nonpathogenic spoilage microorganisms.
Heating at a temperature of 74C for 3-5 seconds or 62C for 30 mins kills the vegetative forms of most pathogenic bacteria
How does Tyndallization work?
The technique used to destroy heat-resistant microorganisms
The process uses steam (30-60 mins) to destroy vegetative bacteria. The steam exposure is repeated a total of three times within 24-hour incubations between exposures. The incubations permit remaining endospores to germinate into heat-sensitive vegetative cells that are destroyed upon subsequent steam exposures
How does an autoclave work?
Steam under pressure (121C and 15 psi for 10-15 mins)
Most effective method for sterilization
Kill vegetative cells and spores
Flash autoclaves use 134C for 3 minutes
How does low-temperature work?
-Inhibits microbial growth and reproduction
-Freezing at -20C or lower stops microbial growth and some microbes will be killed by ice crystals
-Freezers (-30C to -80C) are used in labs for long-term storage of microbial samples
-Freezing is a good method for storing food and other items
What are the 2 physical methods of radiation and how do they work?
UV light:
- have (240 to 280 nm) wavelength range that causes genetic damage for nucleic acids (forming thymine dimers)
-UV radiation has a poor ability to penetrate glass, water, and other substances.
- UV lamps are placed on the ceilings of rooms or in biological safety cabinets to disinfect the air and any exposed surfaces
Ionizing Radiation:
-Carries far greater energy than UV light and penetrates deep into objects.
-Causes direct damage to DNA and destroys bacterial endospores and all microbial cells
-Cathode and gamma rays from cobalt 60 sources are widely used in industrial processes, including cold sterilization of antibiotics, hormones, and many disposable surgical supplies such as gloves, plastic syringes, and specimen containers.
-Can be used to sterilize food
How does the mechanical method of filtration work?
It sterilizes heat-sensitive solutions
-Microfilters with (0.2um) pore size can be used to remove all microbes (Except viruses)
-Air also can be sterilized by filtration –> As in laminar flow biological safety cabinets employing high-efficiency particular air (HEPA) filters, which removes 99.97% of 0.3um particles
What two chemical methods fall under the category of sterilization by gas? How do they work?
Ethylene Oxide (EtO) gas:
-causes damage to DNA and proteins and inactivates microbes.
-in EtO sterilizers, the load is exposed to 10% EtO with CO2 at 50-60C under controlled humidity
-Exposure time must be followed by a prolonged period of aeration
-It is an effective sterilizing agent because it rapidly penetrates packing materials, even plastic wraps
-EtO is good to use for heat-sensitive instruments and materials such as artificial heart valves, heart-lung machine components, sutures, catheters, and plastic Petri dishes.
Formaldehyde Vapor:
An alkylating agent can be used without pressure to decontaminate larger areas such as labs and hospital rooms
Many factors influence the effectiveness of chemical disinfectants and antiseptics, 3 of which are:
-The kind of microbes present
-The nature and the concentration of the disinfectant
-The length of treatment
