Controlling Microbial Growth

Question 1

What are three methods for controlling microbial growth?

Answer 1

Physical, chemical, and antibiotics

Question 2

Sterilization

Answer 2

Destruction of all forms of microbial life including bacterial spores

Question 3

Disinfection

Answer 3

Destruction of microbial pathogens on an inanimate object. Bacterial spores may remain alive

Question 4

Antisepsis

Answer 4

Destruction of microbial pathogens on living object

Question 5

Sanitization

Answer 5

Reduction in the number of pathogens to a level deemed safe by public health guidelines

Question 6

Inhibition

Answer 6

Effectively limiting microbial growth; not necessarily killing of the germ

Question 7

Decontamination

Answer 7

Treatment of an object to make it safe to handle. Process of disinfection or antisepsis

Question 8

Germicide

Answer 8

Any agent that kills microorganisms

Question 9

Bactericide

Answer 9

Any agent that kills bacteria

Question 10

Fungicide

Answer 10

Any agent that kills fungus

Question 11

Viricide

Answer 11

Any agent that kills virus

Question 12

Bacteriostatic agent

Answer 12

Agent prevents further multiplication, not necessarily kill all that are present

Question 13

What are some factors that affect the efficacy of germicide?

Answer 13

TEMPERATURE (more effective at high), TYPES OF MICROORGANISMS (depends on composition of the cell wall, presence or absence of capsule), and ENVIRONMENT (presence of organic material reduces germicidal activity)

Question 14

Thermal death point

Answer 14

Lowest temperature at which all microorganism are killed in 10 minutes

Question 15

Thermal death time

Answer 15

Minimum amount of time required to kill all microorganisms at a given temperature

Question 16

Decimal reduction time (D-value)

Answer 16

Time required for the destruction of 90% microbial population at a given temperature

Question 17

What is the most widely used method of controlling microbial growth?

Answer 17

Heat sterilization

Question 18

What can happen at high temperature?

Answer 18

Three dimensional proteins revert to an irreversible two dimensional structure. Some bacterial create endospores, but vegetative cells die

Question 19

Dry Heat

Answer 19

Used in incineration devices, Bunsen burner, hot-air oven. Sterilization achieved in hot air oven at 170 degrees Celsius in 2 hours.

Question 20

What are the three moist heat methods?

Answer 20

Boiling water, autoclave, and pasteurization

Question 21

What does boiling water do?

Answer 21

Kills microorganisms at 100 degrees Celsius within 2-3 minutes if they are vegetative. But over 2-3 hours to destroy spores

Question 22

What does an autoclave do?

Answer 22

Uses steam (121 degrees Celsius) under pressure (15psi) and sterilization is achieved in 15 minutes

Question 23

What does pasteurization do?

Answer 23

Process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids. It does not kill all organisms, therefore, does not achieve sterilization

Question 24

What are the types of pasteurization?

Answer 24

Holding method, flash method, ultra pasteurization, HTST, UHT

Question 25

What does HTST stand for?

Answer 25

High-Temperature Short-Time

Question 26

What does UHT stand for?

Answer 26

Ultra-heat treatment

Question 27

What is holding flash method?

Answer 27

30 minutes at 62 degrees Celsius

Question 28

what is flash method?

Answer 28

15 seconds at 72 degrees Celsius

Question 29

what is ultra pasteurization?

Answer 29

3 seconds at 82 degrees Celsius

Question 30

What does HTST do?

Answer 30

Designed to extend the refrigerated shelf life of dairy products; 2-3 weeks

Question 31

What does UHT do?

Answer 31

135 degrees C for 1-2 seconds. Kills spores and it's shelf life is up to 9 months.

Question 32

Tyndallization

Answer 32

Sterilization technique of liquids. Liquids are subjected to free steam for 30 minutes on each of 3 successive days

Question 33

What happens on the first successive day?

Answer 33

All vegetating microorganisms, except spores, are killed

Question 34

What happens on the second successive day?

Answer 34

In the overnight period, spores germinate and are killed on second day

Question 35

What happens on the third successive day?

Answer 35

The last few remaining spores germinate on the second evening and killed on the third day

Question 36

What are the four methods of heating process for sterilization of liquid media?

Answer 36

Boiling, autoclave, Pasteurization only if you use HTST, and tyndallization

Question 37

What are the non-heat physical methods of control?

Answer 37

Filtration, drying, lyophilization, cold temperature, radiation

Question 38

What does filtration do?

Answer 38

It avoids the use of heat on sensitive liquids and gases

Question 39

What are two types of filters?

Answer 39

HEPA and Membrane filters

Question 40

What does HEPA stand for?

Answer 40

High Efficiency Particulate Arrestance

Question 41

What does a HEPA filter do?

Answer 41

Type of air filter that removes particles less than .3 micrometers

Question 42

What does a membrane filter do?

Answer 42

Used for liquids, to remove bacteria, the pore size is .15-.22 and for viruses .01

Question 43

Drying

Answer 43

Water is removed from cells they shrivel and die

Question 44

What are two ways of drying?

Answer 44

Put in the cooler or heating the liquid to a lower temperature (ex. 60 degrees Celsius)

Question 45

Lyophilization

Answer 45

Liquid are quick-frozen and simultaneously subject to evacuation, dries the materials. vaccines are preserved this way

Question 46

Cold Temperature

Answer 46

Used in refrigerator to control growth. Microbial metabolism slows down and reproductive rate slows down.

Question 47

What are some ways that microbial growth can be reduced?

Answer 47

Microwaves, UV rays, X-rays, gamma rays, and electrons