Disinfection & Sterilization

Question 1

Compare and contrast sterilization with sanitization

Answer 1

Both are cleaning methods but sterilization involves the destruction of all living microbes, spores, and viruses, sanitation only reduces the number of pathogens/discourages growth

Question 2

What are the physical methods of disinfection

Answer 2

heat
radiation
filtration

Question 3

How does heat attack cells?

Answer 3

destroys proteins and nucleic acids
water is removed

Question 4

the minimum temp at which all bacteria in a culture will die within 10 minutes

Answer 4

Thermal Death Point (TDP)

Question 5

DRT-value (decimal reduction time) defines what?

Answer 5

defines heat resistant bacteria

Question 6

requires LONG periods of exposure

Answer 6

Dry heat

Question 7

faster and effective at low temperatures

Answer 7

Moist heat

Question 8

how does moist heat disrupt cells?

Answer 8

denatures proteins and coagulates them

Question 9

application of steam heat and pressure, kills vegetative cells, bacterial spores, fungi, and viruses in approx. 15 min

Answer 9

Autoclaving

Question 10

Process of autoclaving

Answer 10

items placed in the chamber, air is evacuated by a vacuum pump, and steam is forced into the chamber at a high temperature

Question 11

things that can be sterilized by autoclaving

Answer 11

medical waste
infectious materials
culture media
surgical tools
lab glassware

Question 12

reduces the chances of spoilage and disease in milk

Answer 12

Pasteurization

Question 13

what is not affected by pasteurization?

Answer 13

bacterial SPORES

Question 14

traps microorganisms

Answer 14

Filtration

Question 15

why is filtration useful?

Answer 15

it is useful for sterilizing liquids that can be destroyed by heat

Question 16

how does filtration work?

Answer 16

organisms above a certain size threshold are trapped in the pores of the filter

Question 17

types of radiation

Answer 17

UV
Ionizing

Question 18

Crosslinks nucleic acids rendering organism unable to replicate genetic material

Answer 18

UV Radiation

Question 19

X-ray, Gamma-ray, or microwave radiation create strand breaks in in nucleic acids rendering organism unable to replicate genetic material

Answer 19

Ionizing radiation

Question 20

pros and cons of radiation

Answer 20

active against spores but they can have resistance to low level radiation

Question 21

Physical methods of food preservation

Answer 21

Drying (removes water)
Salting/curing (removes water through osmosis)
Low temps (lower microbial growth rates)

Question 22

chemical agent the is used to kill microbes on living tissue

Answer 22

Antiseptics

Question 23

chemical agents that is used to kill microbes on a non-living surface

Answer 23

Disinfectants

Question 24

High-level disinfectants

Answer 24

Hydrogen peroxide
Chlorine
Chlorine dioxide
Gas vapor

Question 25

Mid-level disinfectants

Answer 25

Alcohol Iodine

Question 26

Low-level disinfectants

Answer 26

Quartenary Ammonium compounds Soap and Hot Water

Question 27

How does hydrogen peroxide destroy cells?

Answer 27

destroys proteins and membranes

Question 28

How does chlorine destroy cells?

Answer 28

highly reactive oxidizer destroys proteins, membrane, and nucleic acids

Question 29

How does gas vapor destroy cells?

Answer 29

disrupting protein functions

Question 30

Chemical disinfectants that are effective against spores

Answer 30

Hydrogen peroxide Chlorine dioxide Chlorine

Question 31

How does alcohol destroy cells?

Answer 31

disrupts membrane bi-layers

Question 32

How does idoine destroy cells?

Answer 32

disrupts protein function and enzymes (oxidizes essential enzymes)

Question 33

neutrophile pH

Answer 33

5-8 (most human pathogens)

Question 34

acidophile pH

Answer 34

0-5

Question 35

alkaliphiles pH

Answer 35

9-11

Question 36

what happens when cells are placed in pH conditions below the optimum?

Answer 36

protons can enter the cell and lower the internal pH to lethal levels

Question 37

How do cells prevent the influx of protons from low pH conditions?

Answer 37

exchange extracellular K+ for intracellular H+ (protons)

Question 38

the diffusion of fluid through semi permeable membrane from an area of low solute concentration to an area of high solute concentration

Answer 38

osmosis

Question 39

how do quartenary ammonium compounds kill cells?

Answer 39

disrupts membrane bi-layers prevents bacteria from dividing

Question 40

how does soap and hot water kill cells?

Answer 40

Molecules of soap disrupt membrane bilayers by inserting themselves into membrane but they are not the same shape

Question 41

things to consider when choosing a chemical agent to clean (5)

Answer 41

1. microbial susceptibility to the agent 2. temp. and pH 3. concentration of the agent needed 4. environment (certain areas more sterile than others) 5. endospore formers