Lecture 7

Question 1

What is sterilization?

Answer 1

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

Question 2

How can sterilization be accomplished?

Answer 2

By incineration, nondestructive heat treatment, certain gases, exposure to ionizing radiation, some liquid chemicals, and filtration.

Question 3

What is disinfection?

Answer 3

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

Question 4

Sanitization is:

Answer 4

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

Question 5

Antisepsis is:

Answer 5

the destruction or inhibition of microorganisms on living tissue

Question 6

Antiseptics:

Answer 6

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

Question 7

Is the use of chemical agents (antibiotics) to kill or inhibit the growth of microorganisms within the host tissue ( inside human or animal body)

Answer 7

Chemotherapy

Question 8

Substances that kill microbes often have the suffix ___

Answer 8

-cide

Question 9

Germicide:

Answer 9

kills pathogens (and many non-pathogens) but not necessarily endospores

Question 10

Sporicide:

Answer 10

eliminates spores

Question 11

Chemicals that do not kill, but do prevent growth have the suffix:

Answer 11

-static
-Example: bacteriostatic and fungistatic

Question 12

What are 3 reasons why sterilization may be used?

Answer 12

-Prevent infection
-Improve surgery or intrusive medical techniques
-Food preservation

Question 13

What are the physical methods of sterilization involving heat?

Answer 13

-Incineration
-Dry heat
-Moist heat
-Pasteurization
-Tydallization
-Autoclave
-Low temperature

Question 14

How does incineration work?

Answer 14

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)

Question 15

How does dry heat work?

Answer 15

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

Question 16

How does moist heat work?

Answer 16

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

Question 17

How does pasteurization work?

Answer 17

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

Question 18

How does Tyndallization work?

Answer 18

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

Question 19

How does an autoclave work?

Answer 19

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

Question 20

How does low-temperature work?

Answer 20

-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

Question 21

What are the 2 physical methods of radiation and how do they work?

Answer 21

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

Question 22

How does the mechanical method of filtration work?

Answer 22

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

Question 23

What two chemical methods fall under the category of sterilization by gas? How do they work?

Answer 23

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

Question 24

Many factors influence the effectiveness of chemical disinfectants and antiseptics, 3 of which are:

Answer 24

-The kind of microbes present
-The nature and the concentration of the disinfectant
-The length of treatment

Question 25

Chemical disinfectants are classified on the basis of their ability to:

Answer 25

-High-level disinfectants kill all agents, except highly resistant bacterial spores
-Intermediate-level disinfectants kill all agents, but not spores
-Low-level disinfectants are active against most vegetative bacteria and lipid-enveloped viruses.

Question 26

What are some examples of liquid, chemical methods of sterilization?

Answer 26

-Phenolics
-Alcohol
-Halogens (Iodine, Chlorine, and Fluorine, etc.)
-Peroxygens (H2O2)
-Surfactants or (Quaternary Ammonium Compounds)
-Heavy Metals

Question 27

How do phenolics work?

Answer 27

-They act by denaturing proteins and disrupting cell membranes
-Phenol and phenolic derivatives (cresol and xylenols) are used as disinfectants in labs and hospitals
-Phenols are a good tuberculocidal and remain active on surfaces for a long time
Example: Lysol

Question 28

How does alcohol work as a sterilizing agent?

Answer 28

-Alcohols are protein denaturants and dissolving membrane lipids
-They are applied to aqueous solutions in the range if 70-95% alcohol
-They are bactericidal and fungicidal but not sporicidal
-Kill most lipid-containing viruses
Most widely used: ethanol and isopropyl alcohol

Question 29

How does Iodine work as a sterilizing agent?

Answer 29

-Iodine is rapidly bactericidal and sporicidal. It is used as a skin antiseptic and kills by oxidizing cell constituents and iodinating proteins.
Iodophors (iodine with carriers such as povidone) are now widely used in cleaning wounds and preparation of skin before surgery

Question 30

How does Chlorine work as a sterilizing agent?

Answer 30

It exists as hypochlorous acid in aq solutions.
-In concentrations of less than one part per million, Cl is lethal to most vegetative bacteria and fungi and inactivates most viruses.
-The efficacy accounts for its use in rendering supplies of drinking water safe and in the chlorination of water in swimming pools
-Chlorine is used in decontaminating surfaces and glassware and used to disinfect surfaces contaminated by human body fluids

Question 31

How does H2O2 work as a sterilizing agent?

Answer 31

It is a powerful oxidizing agent that attacks membrane lipids and other cell components
-Has broad-spectrum activity against viruses, bacteria, yeasts, and bacterial spores
-H2O2 has been useful in disinfecting items such as contact lenses, which are not susceptible to its corrosive effect.

Question 32

How do surfactants work as sterilizing agents?

Answer 32

-They are organic molecules that serve as wetting agents and emulsifiers because they have both polar hydrophilic and nonpolar hydrophobic ends.
-The cation detergents (quaternary ammonium compounds) such as benzalkonium chloride, are highly bactericidal
-They are inactive against M. tuberculosis, spores, and most viruses.
-They disrupt microbial membranes and denature proteins
-Often used as disinfectants for food utensils and small instruments and as skin antiseptics
Market brand: Zephiran and Ceepryn

Question 33

What are some examples of heavy metals used as sterilizing agents?

Answer 33

Mercury, silver, zinc, arsenic, and copper can be used as germicides

Question 34

How do heavy metals work as sterilizing agents?

Answer 34

They bind to cell components such as DNA and proteins and inhibit them.
Silver sulfadiazine has a broad spectrum of activity and is used in burns.
-1% of silver nitrate is often added to the eyes of infants to prevent ophthalmic gonorrhea.
-Copper sulphate is an effective algicide in lakes and swimming pools
These compounds are not sporicidal