Microbio 4-2 disinfection and sterilization

Question 1

What is sterilization?

Answer 1

killing of all microorganisms (bacteria, fungi, viruses)

Question 2

What is germicide? Fungicide? Virocide?

Answer 2

agent used to kill bacteria, fungi, and viruses

Question 3

What is disinfection?

Answer 3

use of a germicidal, fungicidial, and virocidial chemical agent to destroy the potential infectivity of an inanimate object (ie floor)

Question 4

What is antisepsis?

Answer 4

use of chemical agents on the surface of the body to kill or inhibit pathogenic bacteria

Question 5

What does septic mean? Aseptic?

Answer 5

Septic = presence of pathogenic bacteria. Aseptic = absence of pathogenic bacteria.

Question 6

What does santiize mean?

Answer 6

lowering of bacterial content of food utensils or similar objects, without necessarily killing all bacteria (ie dishes washed in soap)

Question 7

What are preservatives?

Answer 7

agent used in small, non-toxic, concentrations to inhibit the growth of organisms (ex: lactic acid, acetic acid, propionic acid, benzoic acid)

Question 8

What is phenol coefficient?

Answer 8

measure of the killing capacity of an agent compared to phenol. Coefficient is the ratio of the minimum killing [ ] of phenol over the minimum killing [ ] of the agent

Question 9

What does a phenol coefficient >1 indicate?

Answer 9

agent works at a [ ] that is lower than that of phenol.

Question 10

What are the 3 main physical agents that are used to kill bacteria?

Answer 10

1) heat (wet/dry), 2) filtration, 3) radiation

Question 11

What is wet heat?

Answer 11

steam under pressure (ie autoclave)

Question 12

Is wet heat more effective than dry heat? Why?

Answer 12

Yes. Because the water molecules speed up the protein denaturation

Question 13

What is wet heat not suitable for?

Answer 13

heat-sensitive materials (ie plastics)

Question 14

What settings would you change if you were to use dry heat instead of wet heat?

Answer 14

increase the temperature and time needed for sterilization

Question 15

When is dry heat more appropriate than wet heat?

Answer 15

used when materials would be damaged by water (ie powders, special surgical dressings)

Question 16

What is pasteurization? How is this different than flash pasteurization?

Answer 16

Pasteurization is essentially mild heating (63˚C for 30 min). Flash pasteurization essentially high temperature, short time (71-72˚C for 15-17 sec). Used in the treatment of wine, milk, juices etc

Question 17

T/F Pasteurization does not kill spores.

Answer 17

True.

Question 18

When would you use filtration over heat?

Answer 18

when liquid material is sensitive to heat (ie it contains enzymes).

Question 19

What are the advantages and disadvantages of using filtration?

Answer 19

Advantages: non-destructive. Disadvantage: inconvenient, esp if large volumes are involved.

Question 20

What are the two types of radiation that is commonly used to sterilize objects?

Answer 20

non-ionizing radiation (ie UV light emitted by mercury vapor lamps), and ionizing radiation (x-rays, gamma rays).

Question 21

How does radation work to sterilize objects? (2)

Answer 21

causes 1) thymidine dimers (interferes with DNA replication) 2) peroxide formation (toxic)

Question 22

Pros and cons of using UV radiation to sterilize objects?

Answer 22

pros: easy to set up. Cons: poor capacity to penetrate anything but air and the thinnest layers of solids/liquids

Question 23

What other physical forms other than heat, filtration, and radiation can be used to sterilize objects?

Answer 23

1) drying, 2) high osmotic pressure, 3) high sugar concentration

Question 24

What are examples of some chemical methods used to sterilize objects? (9)

Answer 24

1) gas, 2) alcohol, 3) halogens, 4) detergents, 5) oxidizing agents, 6) phenols, 7) heavy metals, 8) dyes, 9) aldehydes, 9) preservatives

Question 25

When is gaseous sterilization preferred over other methods of sterilization?

Answer 25

when sterilizing dry materials that are heat-sensitive (ie plasticware, surgical equipment, etc)

Question 26

What is ethylene oxide?

Answer 26

gas that is used to sterilize heat-sensitive materials. Alkylating agent.

Question 27

Ethylene oxide is an explosive agent and can only be used in the presence of this.

Answer 27

high concentrations of CO2

Question 28

When is ethanol preferred over other methods of sterilization?

Answer 28

when using on skin before injections.

Question 29

Does ethanol kill spores?

Answer 29

of course not.

Question 30

What is tincture?

Answer 30

medicine made by dissolving a drug in alcohol

Question 31

What is a tincture of iodine best used for?

Answer 31

(iodine in water-ethanol solution); used as a antiseptic for minor skin wounds or surgery.

Question 32

What are the two halogens that are widely used for sterilization?

Answer 32

Iodine and Chlorine

Question 33

What is chlorine best used for?

Answer 33

sanitizing agent for water supplies, surfaces

Question 34

What are cationic detergents best used for?

Answer 34

anti-sepsis of skin, mucous membranes, and wounds (mostly superficial)

Question 35

How does cationic detergents work?

Answer 35

disrupts bacterial cell membranes and/or protective films

Question 36

What is Zephiran?

Answer 36

cationic detergent that disrupts bacterial cell membranes and/or films

Question 37

Cationic detergents are essentially useless against these two strains of bacteria:

Answer 37

pseudomonas (in burn infections) and mycobacterium tuberculosis.

Question 38

What are two examples of oxidizing agents?

Answer 38

H2O2 and KMNO4

Question 39

What is H2O2 and what is it best used for?

Answer 39

used to treat deep wound infections, where anaerobes reside.

Question 40

H2O2 is essentially useless against which types of bacteria? What is an example?

Answer 40

Any bacteria that is catalase (+), which degrades H2O2 to water and oxygen. Staphylococci is catalase (+)

Question 41

What is KMNO4 used for?

Answer 41

oxidizng agent, mostly as a urethral antiseptic

Question 42

What are phenols? What are limitation(s) in using phenol?

Answer 42

agent that denatures proteins and therefore kills a wide variety of bacteria. Requires high concentrations.

Question 43

What are phenols best used for?

Answer 43

skin antiseptic (ie hexylresorcinol) or textile preservative (triclosan)

Question 44

What are surfactants and what are they best used for?

Answer 44

surface-active agents (soap) or anionic detergents that are weakly bacteriocidal. Best used for removing bacteria and dirtf from skin surfaces.

Question 45

What is triclosan?

Answer 45

phenol/general bacteriocide that is included in soaps and products (ie lotions); inhibits a step in lipid biosynthesis. Resitant mutants mutants have can be isolated.

Question 46

What are two types of heavy metals that are commonly used as a disinfectant?

Answer 46

silver nitrate (eyes of newborns to kill gonococcal organisms). Mercurial compounds (used on minor skin wounds)

Question 47

What is gentian violet and what is it best used for?

Answer 47

anti-fungal agent that is used for candida and tinea (athletes foot)

Question 48

What is formaldehyde and glutaraldehyde?

Answer 48

aldehydes that are used in vaccines (formaldehyde) and areas where blood samples and used syringes are present (glutaraldehyde)

Question 49

What is cidex?

Answer 49

glutaraldehyde

Question 50

What is commmonly used to sterilize vaccines?

Answer 50

formaldehyde

Question 51

What are preservatives?

Answer 51

short chain fatty acids and organic acids that preserve food (ex: lactic acid, acetic acid, propionic acid, benzoic acid, and natural phenolics - thymol and eugenol)

Question 52

How are smoked foods “sterilized?

Answer 52

smoked foods are covered and partially penetrated by phenolic compounds from wood smoke.