Sterilization and disinfection

Question 1

Disinfectant

Answer 1

A chemical agent used on INANIMATE objects to destroy microorganisms. Most do not kill spores

Question 2

Antiseptic

Answer 2

A chemical agent that can safely be used externally on living tissue to destroy microorgansims or to inhibit their growth

Question 3

Bactericidal

Answer 3

refers to an agent that kills bacterial

Question 4

bacteriostatic

Answer 4

refers to an agent that inhibits the growth of bacteria.

Question 5

Sanitizer

Answer 5

a chemical agent that is typically used on food handling equipment and eating utensils to reduce bacterial numbers so as to meet public health standards. Sanitization may simply refer to thorough washing with only soap or detergent.

Question 6

Germicide

Answer 6

an agent capable of killing microbes rapidly; some such agents effectively kill certain microorganism but only inhibit the growth of others

Question 7

Viricide

Answer 7

an agent that inactivates viruses

Question 8

fungicide

Answer 8

an agent that kills fungi

Question 9

Sporocide

Answer 9

An agent that kills bacterial endospores or fungal spores

Question 10

Filler based essay

Answer 10

also known as the filler paper method
It uses small filler paper disks, each soaked with a different chemical agent. The disks are placed on the surface of an agar plate that has been inoculated with a test organism. A different plate is used for each test organism. After incubation, a chemical agent that inhibits growth of a test organisms is identified by a clear area around the disk where the bacteria have been killed.

Question 11

Use-Dilution Test

Answer 11

uses standard preparations of certain test bacteria. A broth culture of one of those bacteria is coated onto small stainless steel cylinderss and allowed to dry. Each cylinder is then dipped into one of several dilutions of the chemical agent for 10 minutes, removed, rinsed with water, and placed into a tube of broth. The tubes are incubated and then observed fro the presence or absence of growth. Agents that prevent growth at the greatest dilutions are considered the most effective. Believed to be more effective than phenol coefficient

Question 12

Phenol coefficient

Answer 12

since lester introduced phenol (carbolic acid) as a disinfectant in 1867, it has been the standard disinfectant to which other disinfectants are compared under the same conditions. The result of this comparison is called the phenol coefficient. Two organisms, salmonella typhi, a pathogen of the digestive system, and staphylococcus aureus, acommon wild pathogen, are typically used to determine phenol coefficients. A disinfectant with a phenol coefficient of 1.0 has the same effectiveness as phenol. A coefficient less than 1.0 means that the disinfectant is less effective than phenol. A coefficient greater than 1.0 means that it is more effective. The test provides an acceptable means of evaluating the effectiveness of chemical agents derived from phenol, but it is less acceptable means of evaluating the effectiveness of chemical agents derived from phenol, but it is less acceptable means of evaluating the effectiveness of chemical agents derived from phenol, but it is less acceptable for other agents.

Question 13

An ideal disinfectant should

Answer 13

• be fast acting even in the presence of organic substances, such as those in body fluids
• be effective against all types of infectious agents without destroying tissues or acting as a poison if ingested
• easily penetrate material to be disinfected without damaging or discoloring the material
• be easy to prepare and stable even when exposed to light, heat, or other environmental factors
• be inexpensive and easy to obtain and use
• not have an unpleasant odor

Question 14

Bacterial cell components that chemical agents damage are

Answer 14

• proteins
• membranes
• nucleic acids
• energy producing systems

Question 15

reactions that affect proteins

Answer 15

alteration of a protein is called denaturation. This is where hydrogen and disulfide bonds are disrupted, and the structural shape of the protein is destroyed. These reactions include: hydrolysis, oxidation, and the attachment of atoms or chemical groups

Question 16

Reactions that affect membranes.

Answer 16

surfactants and wetting agents

Question 17

Surfactants

Answer 17

soluble compounds that reduce surface tension, just as soaps and detergents break up grease particles in dishwater.
Dissolve lipids, disrupt membranes, and inactivate enzymes in high concentrations.

Question 18

Wetting agents

Answer 18

often used with other chemical agents to help the agent penetrate fatty substances

Question 19

Reactions that affect other cell compontents

Answer 19

other cell components include nucleic acids and energy producing systems. Alkylating agents can replace hydrogen on amino or alcohol groups in nucleic acids. Certain dyes such as crystal violet interfere with cell wall formation

Question 20

Soaps and Detergents

Answer 20

lower surface tension, make microbes accessible to other agents.

washing hands

Question 21

acids

Answer 21

lower pH and denature proteins

food preservation

Question 22

Alkalis

Answer 22

Raise pH and denature proteins

found in soaps

Question 23

Heavy Metals

Answer 23

dentature proteins

mercury compounds to disinfect skin an inanimate objects, silver nitrate is used to prevent gonococcal infections, copper to inhibit algal growth, and selenium to inhibit fungal growth

Question 24

Halogens

Answer 24

oxidize cell components in absence of organic matter

chlorine used in water to kill pathogens

Question 25

alcohols

Answer 25

denature proteins when mixed with water

isopropyl alcohol used to disinfect skin

Question 26

phenols

Answer 26

disrupt membranes, denature proteins, inactivate enzymes

phenol used to disinfect surfaces and destroy discarded cultures

Question 27

Oxidizing agents

Answer 27

Disrupt structure of proteins and nucleic acids

Hydrogen Peroxide used to clean puncture wounds

Question 28

Alkylating Agents

Answer 28

disrupt structure of proteins and nucleic acids

formaldehyde used to inactivate viruses

Question 29

Dyes

Answer 29

may interfere with replication or block cell wall synthesis

crystal violet used to treat some protozoan and fungal infections

Question 30

Thermal Death Point

Answer 30

the temp that kills all the bacteria in a 24 hr old broth culture at neutral pH in 10 min

Question 31

thermal death time

Answer 31

the time required to kill all the bacteria in a particular culture at a specified temp

Question 32

Three ways to kill microbes

Answer 32

dry heat, moist heat, and pasteurization

Question 33

Dry Heat

Answer 33

does most of its damage by oxidizing molecules and penetrates stuff more slowly than moist heat. It is usually used to sterilize metal objects and glassware and is the only suitable means of sterilizing oils and powder.

Question 34

Moist Heat

Answer 34

destroys microorganisms mainly by denaturing proteins; the presence of water molecules helps disrupt the hydrogen bonds and other weak interactions that hold proteins in their 3d shapes. Destroys vegetative cells of most bacteria and fungi, also inactivates some viruses

sterilizing canned food and autoclaving sterilizes not metal hospital and laboratory equipment.

Question 35

Pasteurization

Answer 35

doesn’t achieve sterility but does kill pathogens in milk, other dairy products, and beer

Question 36

Other antimicrobial agents

Answer 36

UV light, drying, ionizing radiation, filtration, and osmotic pressure

Question 37

Physical antimicrobial agents

Answer 37

dry heat, moist heat, pasteurization, refrigeration, freezing, drying, freeze drying, ultraviolet light, ionizing radiation, microwave radiation, strong visible light, sonic and ultra sonic waves, filtration membranes, osmotic pressure

Question 38

refrigeration

Answer 38

slows the rate of enzyme controlled reactions

used to keep foods fresh for a few days, does not kill microorganisms

Question 39

Freezing

Answer 39

greatly slows down the rate of most enzyme controlled reactions

used to keep foods fresh for a few months, does not kill microorganisms

Question 40

Drying

Answer 40

inhibits enzymes

used to preserve some fruits and vegetables, preserves food because the absence of water inhibits the action of enzymes

Question 41

Freeze Drying

Answer 41

inhibits enzymes

preserves microorganisms for years and can manufacture instant coffees

Question 42

UV light

Answer 42

Denatures proteins and nucleic acids

used to reduce the # of microorganisms in air operating rooms, animal rooms, and where cultures are transferred

Question 43

Ionizing Radiation

Answer 43

denatures proteins and nucleic acids

used to sterilize plastics and pharmaceutical products and to preserve foods. X-rays and gamma rays

Question 44

Microwave Radiation

Answer 44

absorbs water molecules, then releases microwave energy as heat

cannot be used reliably to destroy microbes except in special media sterilizing equipment

Question 45

Strong visible light

Answer 45

oxidation of light sensitive materials

can be used with dyes to destroy bacteria and viruses; may help sanitize clothing

Question 46

Sonic and ultrasonic sound waves

Answer 46

cause cavitation

not practical means of killing microorganisms but useful in fractionating and studying cell components

Question 47

Filtration Membranes

Answer 47

Mechanically removes microbes

used to sterilize media, pharmaceutical products, and vitamins, in manufacturing vaccines, and in sampling microbes in air and water. like using a strainer

Question 48

Osmotic pressure

Answer 48

removes water from microbes

used to prevent spoilage of foods such as pickles and jellies.