(exam 1) chapter 7 control of microbial growth

Question 1

what does sepsis mean?

Answer 1

describes bacterial contamination

Question 2

what does asepsis mean?

Answer 2

absence of (without) significant contamination

Question 3

what does aseptic technique prevent?

Answer 3

prevent microbial contamination

Question 4

what is sterilization?

Answer 4

removing and destroying all microbial life (typically commercial sterilization canned goods)

Question 5

what is disinfection?

Answer 5

destroying harmful microorganisms (typically with chemical disinfectants)

Question 6

what is sanitation?

Answer 6

lowering microbial counts on eating utensils to safe levels

Question 7

what is antisepsis?

Answer 7

acts of destroying harmful microorganisms from living tissue (typically with antiseptics)

Question 8

what is degerming?

Answer 8

the mechanical removal of microbes from a limited area

Question 9

what is biocide (germicide)?

Answer 9

treatments that kill microbes

Question 10

what is bacteriostasis?

Answer 10

inhibiting microbe growth (not killing)

Question 11

what usually causes microbe death and what is the death rate?

Answer 11

heat or chemical; microbes die at a constant rate

Question 12

what does the effectiveness of the treatment depend on? (four things)

Answer 12

1) number of microbes
2) environment (organic matter- inhibits effectiveness; temperature-heat increases effectiveness; biofilms-protect the microbes)
3) time of exposure
4) microbial characteristics

Question 13

what are three primary effects of microbial control agents?

Answer 13

1) alterations of membrane permeability (damage to plasma membrane)
2) damage to proteins (enzymes)
3) damage to nucleic acids (can’t replicate)

Question 14

how does heat control microbial growth?

Answer 14

denatures proteins (denatures enzymes)

Question 15

what are two moist heat sterilization techniques?

Answer 15

1) boiling

2) free flowing steam (via autoclave)

Question 16

how does boiling control microbial growth?

Answer 16

denatures proteins- kills most microbes in ~10min BUT endospores are RESISTANT to this method

Question 17

how does free flowing steam control microbial growth?

Answer 17

uses an autoclave (121 C at 15 psi for 15 min) kills ALL organisms AND ENDOSPORES (but cannot kill prions)

Question 18

what is an autoclave?

Answer 18

device that uses steam under pressure for sterilization

Question 19

how does pasteurization (heat) control microbial growth?

Answer 19

Denatures proteins- by using very high temperatures for a short time; Eliminates pathogenic bacteria but
thermoduric organisms survive- used for milk

Question 20

how does sterilization (heat) control microbial growth?

Answer 20

Kills via oxidation - Ultra-high temps for very short time

(140 C for 4 sec) used for milk in locations where refrigeration is not available

Question 21

how does dry heat sterilization (heat) control microbe growth?

Answer 21

Burns contaminants to ashes! Kills by oxidation (Flaming, Incineration or Hot-air sterilization)

Question 22

how does filtration control microbial growth?

Answer 22

passage of substance through a screen-like material (used for heat-sensitive materials)
High-efficiency particulate air (HEPA) filters remove microbes > 0.3 μm in diameter

Question 23

how do low temperatures control microbial growth?

Answer 23

Have a bacteriostatic effect - stalls their growth

Psychotrophs still grow BUT slowly! Pathogenic bacteria (except Listeria) don’t grow at cold temps “stuns growth”

Question 24

how does high pressure control microbial growth? What does it alter?

Answer 24

Applies to liquids; Alters protein and carbohydrate molecular structures

Question 25

how does desiccation control microbial growth?

Answer 25

Without water, microbes can not reproduce but can remain viable

Question 26

how does Osmotic Pressure

control microbial growth?

Answer 26

(damaging the plasma membrane) high concentrations of salts and sugars cause a hypertonic environment which causes plasmolysis

Question 27

what are two types of radiation methods to control microbial growth?

Answer 27

1) Ionizing radiation (X-rays, gamma rays, electron beams)

2) Nonionizing radiation (UV light)

Question 28

how does Ionizing radiation control microbial growth?

Answer 28

(X-rays, gamma rays, electron beams) Ionizes water to create reactive hydroxyl radicals which damages DNA by causing lethal mutations

Question 29

how does Nonionizing radiation control microbial growth?

Answer 29

(UV light) damages DNA by creating thymine dimers -
Disadvantage: Not very penetrating; microbe must be directly exposed
“Germicidal” lamps

Question 30

microwaves kill heat BUT

Answer 30

they are not especially antimicrobial

Question 31

what are the only two chemical methods of controlling microbial growth that we discussed?

Answer 31

1) dilution tests

2) disk-diffusion method

Question 32

how does dilution tests (chemical methods) control microbial growth?

Answer 32

1) Metal cylinders are dipped into test bacteria and dried
2) Cylinders are placed in disinfectant for 10 min at 20°C
3) Cylinders are transferred to culture media to determine whether the bacteria survived treatment

Question 33

how does the disk diffusion method (chemical method) control microbial growth?

Answer 33

1) Filter paper disks are soaked in a chemical and placed on a culture
2) Look for zone of inhibition around disks