Ch 7 The Control Of Microbial Growth

Front 1

What is sterilization?

Back 1

Destruction or removal of all forms of microbial life, including endospores. (p.188)

Front 2

What is commercial sterilization?

Back 2

Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food.

Front 3

Define disinfection-

Back 3

Destruction of vegetative pathogens. p.188

Front 4

Define antisepsis

Back 4

Destruction of vegetative pathogens on living tissue. p.188

Front 5

Define degerming

Back 5

Removal of microbes from a limited area, such as the skin around the injection site. p.188

Front 6

Define sanitization

Back 6

Treatment intended to lower microbial counts on eating and drinking utensils to safe public health levels. p.188

Front 7

Why is sterilization so difficult to achieve?

Back 7

Because sterilization is the removal or destruction of ALL forms of microbial life. p.188

(keep in mind that a bacterial death or decline phase is logarithmic, and that survivors turn on the expression of genes whose products make them very difficult to kill.)

Front 8

What are some enviornmental factors that will affect the rate of microbial death?

Back 8

The presence of organic matter often inhibits the action of chemical antimicrobials.

(Ex: In hospitals the presence of organic matter in blood, vomit, or feces influences the selection of disinfectants.) p.190

Front 9

What is biocide or germicide?

Back 9

kills microorganisms (usually with certain exceptions, such as endospores) p.189

Front 10

What does bacteriostasis mean?

Back 10

Treatment that only inhibits the growth and multiplication of bacteria. Once bacteriostatic agent is removed, growth might resume. p.189

Front 11

What does sepsis mean?

Back 11

From the Greek for decay or putrid, indicates bacterial contamination as in septic tanks for sewage treatment. p.189

Front 12

What does asepsis mean?

Back 12

the absence of significant contamination. p.189

Front 13

What are some factors that influence the effectiveness of antimicrobial treatments?

Back 13

1) The number of microbes.

2) Environmental influences. (presence of organic matter)

3) Time exposure (often req. extended amt. of exposure for more resistant microbes or endospores to be affected.)

4) Microbial characteristics

p.189-190

Front 14

What cellular structures are the targets of various microbial control agents?

Back 14

A microorganism's plasma membrane, located just inside the cell wall.

Damage to the lipids or proteins of the plasma membrane by antimicrobial agents cause cellular contents to leak into the surrounding medium and interferes w/ the growth of the cell. p.190

Front 15

What are some physical methods for controlling microbial growth to preserve foods, used in the Stone Age?

Back 15

1) Desiccation (drying)

2) Osmotic pressure (salting)

p.190

Front 16

How can heat be used to sterilize objects?

Back 16

Heat appears to kill microorganisms by denaturing their enzymes; the resultant changes to the 3-dimensional shapes of these proteins inactivate them. p.191

Front 17

What factors determine what application of heat will be used?

Back 17

1) Heat resistance. Thermal death point (TDP) is the lowest temp. at which all the microorganisms in a particular liquid suspension will be killed in 10 mins.

2) Length of time required. Thermal death time (TDT), the min. length of time for all bacteria in a particular liquid culture to be killed at a given temperature.

3) Decimal reduction time (DRT or D value): time in minutes in which 90% of population of bacteria at a given temp. will be killed.

p.191

Front 18

Both refrigeration and pasteurization are used to control microbial growth in food. Are these strategies bacteriostatic or bacteriocidal?

Back 18

These strategies are bacteriostatic.

They lower microbial numbers which prolongs milks good quality under refrigeration. p.193

Front 19

How does moist heat kill microorganisms?

Back 19

Primarily by the coagulation of proteins (denaturation), which is caused by breakage of the hydrogen bonds that hold the proteins in their three-dimensional structure.

(ex: watch an egg white frying)
p.191

Front 20

Is boiling always a reliable sterilization procedure?

Back 20

No. Some endospores and viruses are not destroyed w/in 10 mins. of boiling.

Some Hepititis viruses can survive 30 mins. of boiling, & some bacterial endospores can resist boiling for more than 20 hrs.

HOWEVER, brief boiling at high altitudes, will kill most pathogens.
(Ex: boiling to sanitize baby bottles) p.191

Front 21

What is a reliable sterilization procedure using moist heat?

Back 21

In autoclaving high temperatures above boiling temperatures are achieved by steam under pressure in an autoclave.

This method is preferred unless the material to be sterilized can be damaged by heat or moisture.

p.191

Front 22

The higher the -----in the autoclave, the higher the----.

Back 22

pressure

temperature.

p.192

Front 23

Autoclaving is used to sterilize...

Back 23

culture media, instruments, dressings, intravenous equipment, applicators, solutions, syringes, transfusion equipment and numerous other items that can withstand high temperatures and pressures.

p.192

Front 24

Heating is less efficient in foods that are more -----, and ----in food can have a protective effect on microorganisms.

Back 24

viscous

fats

p.193

Front 25

Milk pasteurization today uses high temperatures 72 degrees celsius for only 15 seconds. This treatment is known as...

Back 25

High-temperature short-time (HTST) pasteurization, is applied as the milk flows continuously past a heat exchanger. Kills pathogens and lowers total bacterial counts, so the milk keeps well under refrigeration.

p.193

Front 26

What is the cellular target of Moist heat: boiling or flowing steam?

Back 26

mechanism of action:
protein denaturation

Kills vegetative bacterial & fungal pathogens & almost all viruses w/in 10 mins.; less effective on endospores.

p.197

Front 27

What is the cellular target of Moist heat: Autoclaving?

Back 27

mechanism of action:
Protein denaturation

Very effective method of sterilization; at about 15psi of pressure (121 degrees Celsius), ALL vegetative cells & their endospores are killed in about 15 mins.

Preferred use:
Microbiological media: solutions, linens, utensils, dressings, equipment, & other items that can withstand temperature and pressure.

p.197

Front 28

What is the cellular target of Moist heat: Pasteurization?

Back 28

mechanism of action:
Protein denaturation.

Heat treatment for milk (72 degrees Celsius for about 15 secs.) that kills ALL pathogens and MOST nonpathogens.

Preferred use:
Milk, cream, & certain alcoholic beverages (beer and wine)

Front 29

What is the cellular target for Dry Heat: Direct Flaming?

Back 29

mechanism of action:
Burning contaminants to ashes.

Very effective method of sterilization.

Preferred use:
Inoculating loops.

p.197

Front 30

What is the cellular target for Dry Heat: Incineration?

Back 30

mechanism of action:
Burning to ashes.

Very effective method of sterilization.

Preferred use:
paper cups, contaminated dressings, animal carcasses, bags and wipes.

p.197

Front 31

What is the cellular target for Dry Heat: Hot-air sterilization?

Back 31

mechanism of action:
oxidation.

Very effective method of sterilization but reqs. temperature of 170 degrees Celsius for about 2 hrs.

Preferred use:
Empty glassware, instruments, needles, and glass syringes.

p.197

Front 32

How does Filtration work?

Back 32

mechanism of action:
Separation of bacteria from suspending liquid.

Removes microbes by passage of a liquid or gas through a screen like material. Most filters in use consist of cellulose acetate or nitrocellulose.

Preferred use:
sterilizing liquids (enzymes, vaccines) that are destroyed by heat.

p.197

Front 33

What is the cellular target of Cold: Refrigeration?

Back 33

mechanism of action:
decreased chemical reactions & possible changes in proteins.

Has BACTERIOSTATIC effect.

Preferred use:
food, drug, and culture preservation.

p.197

Front 34

What is the cellular target of Cold: Deep Freezing?

Back 34

mechanism of action:
decreased chemical reactions and possible changes in proteins.

An effective method for preserving microbial cultures, in which cultures are quick-frozen between -50 degrees Celsius and -95 degrees Celsius.

Preferred use:
Food, drug, and culture preservation.

p.197

Front 35

What is the cellular target of Cold: Lyophilization?

Back 35

mechanism of action:
Decreased chemical reactions and possible changes in proteins.

Most effective method for LONGterm Preservation of microbial cultures; water removed by high vaccum at low temperature.

Preferred use:
Food, drug, and culture preservation.

p.197

Front 36

What is the cellular target of High Pressure?

Back 36

mechanism of action:
Alteration of molecular structure of proteins and carbohydrates.

Preservation of colors, flavors and nutrient values.

Preferred use:
Fruit juices.

p.197

Front 37

What is the cellular target of Desiccation?

Back 37

mechanism of action:
Disruption of metabolism.

Involves removing water from microbes; PRIMARILY BACTERIOSTATIC.

Preferred use:
Food preservation.

p.197

Front 38

What is the cellular target for Osmotic Pressure?

Back 38

mechanism of action:
Plasmolysis.

Results in loss of water from microbial cells.

Preferred use:
Food preservation.

p.197

Front 39

What is the cellular target of Radiation: Ionizing?

Back 39

mechanism of action:
Destruction of DNA.

Not widespread in routine sterilization.

Preferred use:
sterilizing pharmaceuticals and medical and dental supplies.

p.197

Front 40

What is the cellular target of Radiation: Nonionzing?

Back 40

mechanism of action:
Damage to DNA.

Radiation is NOT very penetrating.
(organisms to be killed must be directly exposed to rays.p.196)

Preferred use:
Control of closed environment w/ UV (germicidal) lamp.

p.197

Front 41

How does filtration work? Does this method of microbial control kill microorganisms?

Back 41

Passage of a liquid or gas through a a screenlike material w/ pores small enough to retain microorganisms. A vacuum is created in the receiving flask; air pressure then forces the liquid through the filter. p.194

No.

Front 42

Radiation that kills microorganisms (sterilizing radiation) is of two types:

Back 42

ionizing and nonionizing. p.195

Front 43

Gamma rays, X-rays or high energy beams are forms of...

Back 43

Ionizing radiation. Has a shorter wavelength than that of nonionizing radiation, less than about 1nm. Carries More energy.

Front 44

What is the cellular target of Nonionizing radiation?

Back 44

UV light damages DNA of exposed cells by causing bonds to form between adjacent pyrimidine bases, usually thymines, in DNA chains.

Thymine dimers inhibit correct replication of the DNA during reproduction of the cell. p.196

Front 45

What is a major disadvantage of UV light as a disinfectant?

Back 45

It is not very penetrating, so the organisms to be killed must be directly exposed to the rays.

side note: prolonged exposure can cause burns and skin cancer in humans. p.196

Front 46

How can the effectiveness of a disinfectant be determined?

Back 46

By the number of cultures that grow. p.198

Front 47

Lister was the first to use-----to control surgical infections in the operating room.

Back 47

phenol (carbolic acid)

Now, rarely used as an antiseptic or disinfectant b/c it irritates the skin and has a disagreeable odor. p.198

Front 48

Soaps and detergents are examples of--------

Back 48

surfactants: surface-active agents.

important function in the Mechanical removal of microbes through scrubbing. p.202

Front 49

What are quats?

Back 49

Quaternary ammonium compounds.

they are modifications of the four valence ammonium ion.

Strongly Bacteriocidal against gram (+) bacteria, less active against gram (-) bacteria.

Also fungicidal, amoebicidal, & virucidal against enveloped viruses.

They change the cell's permeability & cause the loss of essential cytoplasmic constituents, such as potassium.

p.202-203

Front 50

What are the major drawbacks of using ethylene oxide and beta-propiolactone?

When would they be used?

Back 50

They are suspected carcinogens. p.205

Used on medical supplies and equipment.

Ex: ethylene oxide chambers, large enough to sterilize mattresses.

Front 51

Why are antibiotics not included in this chapter?

Back 51

The compounds discussed in this chapter are NOT generally useful in the treatment of diseases.

Because antibiotics are used in chemotherapy, antibiotics and the pathogens against which they are active will be discussed in Ch. 20. p. 207

Front 52

What is the best method for sterilization of an enzyme solution?

Back 52

Filtration.

(Micro CD)

Front 53

Some antimicrobial treatments kill microbes; some inhibit growth. Which term refers to an agent that inhibits bacterial growth?

Back 53

Bacteriostatic

(Micro CD)

Front 54

Pasteurization was first used by Pasteur to control spoilage of....

Back 54

Wine.

(Micro CD)

Front 55

Packages of milk and coffee creamers may be stored w/out refrigeration if they have been sterilized by...

Back 55

Ultra high temperature treatment (UHT)

(Micro CD)

Front 56

The 1st disinfectant used by Lister was...

Back 56

phenol.

(Micro CD)

Front 57

Alcohol is most effective when used as a --------- solution.

Back 57

70%

(Micro CD)

Front 58

----------- is a compound found in antimicrobial soaps that target gram-positive bacteria.

Back 58

Triclosan.

(p.200)