Ch.7 Controlling Microbial Growth

Question 1

what is sterilization?

Answer 1

removal/destruction of all living microbes
and spores and viruses

Question 2

what is disinfection?

Answer 2

killing of vegetative pathogens on a surface
(inanimate objects); usually w/chemicals

Question 3

what is antisepsis?

Answer 3

reduction of pathogens from living tissue
(sepsis /asepsis)

Question 4

what is degerming?

Answer 4

removal of transient microbes from skin by mechanical
cleansing or by an antiseptic.

Question 5

what is sanitation?

Answer 5

Relates to hygienic practices; reduction in overall total
microbial numbers to safe level

Question 6

what can reduce cell numbers at a negative logarithmic rate?

Answer 6

exposure to antimicrobials

Question 7

what happens during bariostatic treatment?

Answer 7

growth inhibitory

no cell killing

Question 8

what happens during bactericidal treatment?

Answer 8

Cell killing

Cells remain intact

Question 9

what happens during bacteriolytic treatment?

Answer 9

cell killing

cells are lysed(destroyed)

Question 10

Killing occurs at what?

Answer 10

some logarithmic rate NOT all at once

Question 11

what does the D value=?

Answer 11

1 minute

Question 12

what is the efficacy of antimicrobial agent ?

Answer 12

decimal reduction time or Dvalue

Question 13

what occurs during the decimal reduction time or D-value?

Answer 13

time for agent to kill 90% of population

Question 14

what factors influence the efficacy of antimicrobial treatments?

Answer 14

1. number/type of microbes present
2. organic land
3. exposure time/dose

4.pH, temperature

Question 15

what are the targets of antimicrobial agents?

Answer 15

plasma membrane

proteins(through heat,pH or heavy metal)

nucleic acids (breakage,denaturation or chemical alteration

Question 16

what are the physical agents to control microbes?

Answer 16

1.High temp & pressure

2.Pasterizuation

3.Dry Heat Sterilization

Question 17

how is high temp used to control microbes?

Answer 17

-Boiling: 10 minutes @ 100⁰C

– Steam under pressure

– Autoclave: 15
psi/121⁰C/15 min

Question 18

how is pasteurization used to control microbes?

Answer 18

mild heat; for
food/beverages

– Low temp/Long time (LTLT):
63°C/30 minutes

– Flash pasteurization; short time (HTST): 72°C/15 seconds (flash pasteurization)

– Ultra-high temperature (UHT):
140°C/>1 second

Question 19

how is dry heat sterilization used to control microbes?

Answer 19

Incineration

Hot air-170 C 2 hr

Autoclave 121C 15 min

Question 20

physical agents to kill microbes:

Answer 20

4.Cold Temp

5.Filtration

6.Desiccation

7.Osmotic Pressure

8.Nonionizng radiation

9.Ionizing radiation

Question 21

what does cold temp do to microbes?

Answer 21

slows growth

Question 22

what is cold temp used for?

Answer 22

microbial preservation

cell preservation

food preservation

Question 23

what is filtered to kill microbes?

Answer 23

aqueous solutions and air

Question 24

what uses membrane filtration?

Answer 24

heat liable liquids

0.45 um, 0.2 um pore sizes

Question 25

what removes microbes >0.3 um?

Answer 25

HEPA(air)

Question 26

what is the best for surface disinfection?

Answer 26

non-ionizing radiation

Question 27

what is the effect of non ionizing radiation?

Answer 27

creates mutations

abnormal DNA bonds

does not peneratate well

wavelength 200-300 um

Question 28

what are the effects of ionizing radiation?

Answer 28

DNA breakages

ionizes water to release OH

fragments nucleic acids

penetration radiation

wave length <0.1 nm

Question 29

what chemical methods of control?

Answer 29

1.Pheonolics

2.Halogens

3.Alochols

4.heavy metals

5.surface active surfeits

6.chemical preservative

7.Gaseous Sterilants

Question 30

how are phenolics used as chemical methods of control?

Answer 30

disrupt lipids of plasma
membrane & denature proteins.

– Remain active on surfaces after application.

Question 31

how are halogens used as chemical methods of control?

Answer 31

alter protein synthesis & membranes

ex: iodine

chlorine bleach: oxidizing agents

Question 32

what does alcohol do as a chemical method of control?

Answer 32

requires water

denature proteins

dissolves lipids

ex:ethanol and isopropanol

Question 33

what are heavy metal use for as chemical method?

Answer 33

denature proteins

can be toxic–> use ay low concentration

ex:
Ag,Hg, and Cu

Question 34

how are surface-active agents, and surfactants used for chemical methods?

Answer 34

Mimic phospholipid
structure and disrupt
membrane integrity

Question 35

how are chemical preservatives used as control chemical methods?

Answer 35

control molds/bacteria in foods/cosmetics

– Organic acids: alter internal pH; inhibit metabolism

Ex:
* Sorbic acid, benzoic acid

Question 36

how are gaseous sterilants used as chemical methods?

Answer 36

denature, modify proteins

ex:
– For heat->sensitive material -plastics

– Ethylene oxide

Question 37

what is resistance to disinfectants dependent on?

Answer 37

concentration

Question 38

is this true or false

Resistance more likely at lower concentrations of disinfectant

Answer 38

true

Question 39

microbial resistance to biocides

most resistant to least resistant

Answer 39

prions

endospores of bacteria

mycobacteria

cysts of protozoa

negative protozoa

gram-negative bacteria

fungi, including most fungal spores

viruses without envelopes

gram-postive bacteria

viruses with lipid envelopes

Question 40

what method kills endospores?

Answer 40

sterilization

Question 41

what is the use-dilution test?

Answer 41

metal rings dipped in test bacteria

dried cultures are placed in disinfectant for 10 min at 20 C

rings are transferred to culture to determine whiter bacteria survived treatment

Question 42

what is the disk diffusion method?

Answer 42

filter disks soaked in chemical agent are placed on plate inoculated with bacteria

analyze zones of inhibition (proportional to effectiveness of disfencatnt)