The control of microbial growth

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Microbiology
Chapter 7
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1

Which of the following is the best method to sterilize heat-labile solutions

membrane filtration

2

which of the following best describes the pattern of microbial death

the cells in a population die at a constant rate

3

which of the following substances is used for surgical hand scrubs

chlorhexidine

4

which of the following pairs of terms is mismatched

bateriostatic -- kills vegetative bacterial cells

5

the antimicrobial activity of chlorine is due to which of the following

the formation of hypochlorous acid

6

which of the following regarding antimicrobial control agents is false

alcohols effectively inactivate nonenveloped viruses by attacking lipids

7

which of the following does not achieve sterilization

pasteurization

8

which of the following is a limitation of the autoclave

it cannot be used with heat-labile materials

9

an agent used to reduce the number of bacteria on a toilet would most accurately be called

disinfectant

10

application of heat to living cells can result in all of the following except

decreased thermal death time

11

which of the following disinfectant acts by disrupting the plasma membrane

bisphenols

12

all of the following substances are effective against nonenveloped viruses except

alcohol

13

which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes

freezing

14

which concentration of ethanol is the most effective bactericide

70%

15

all of the following factors contribute to hospital-acquired infections except

all of these factors may contribute to hospital-acquired infection

some bacteria metabolize disinfectants

gram-negative bacteria are often resistant to disinfectant

invasive procedures can provide a portal of entry for bacteria

bacterial may be present in commercial products such as mouthwash `w

16

which of the following treatments is the most effective for controlling microbial growth

they are equivalent treatments

17

which of the following could be used to sterilize plastic petri plates in a plastic wrapper

gamma radiation

18

In figure 7.1 what is the thermal death time

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60 minutes

19

In figure 7.1 the thermal death point for this culture is

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answer cannot be determined

20

in figure 7.1 the decimal reduction time (D value) for the culture, which is defined as the time to reduce a population by one log, is approximately

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10 minutes

21

which of the following results in lethal damage to nucleic acids

heat, radiation, and some chemicals

22

in table 7.1 which compound was the most effective against staphylococcus

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C

23

in table 7.1 which compound was bactericidal

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answer cannot be determined

24

all of the following substances are used to preserve foods except

biguanides

25

all of the following are effective for destroying prions except

boiling

26

all of the following are methods of food preservation except

microwaves

27

which of the following is most resistant to chemical biocides

gram-negative bacteria

28

the thermal death time is the time needed to kill all the bacteria in a particular culture at a certain temperature

true

29

pseudomonas has been found growing in quarternary ammonium compounds

true

30

moist heat destroys organisms by denaturing proteins

true

31

some antimicrobial chemicals are considered to be disinfectants and antiseptics

true

32

the pH of the medium has no effect on the activity of the disinfectant being applied

false

33

autoclaving is the most effective method of moist heat sterilization

true

34

microorganism placed in high concentrations of salts and sugars undergo lysis

false

35

sterilization

removal or destruction of all microorganism

36

sterilant

sterilizing agent

37

commercial sterilization

limited heat treatment

38

disinfectant

control directed at destroying harmful microorganisms

39

antisepsis

when treatment is directed at living tissue

40

degerming

when the skin is swabbed with alcohol before vaccination

41

sanitization

intended to lower microbial counts

42

biocide/gemicide

kills microorganisms

43

sepsis

bacterial contamination

44

what is the rate of microbial death

the number of microbes

environmental influences

time of exposure

microbial characterisitics

45

What is thermal death point

the lowest temperature at which all the microorganisms in a particular liquid suspension will be killed in 10 minutes

46

What is thermal death time

the minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature

47

what is decimal reduction time

time in which 90% of a population of bacteria at a given temperature will be killed

48

how does moist heat kill microorganisms

by coagulating proteins

49

what is an autoclave

preferred method of sterilization in health care environments

50

what are retorts

large industrial autoclaves

51

pressure and temperature in an autoclave

higher the temperature (121oC), the higher the pressure (150lbs/psi)

52

pasteurization

elimination of pathogenic microbes

53

thermoduric

heat-resistant bacteria

54

high temperature short-time pasteurization

most milk pasteurization uses temperature of 72oC but for only 15 secs

also lower bacterial counts

55

utlra-high-temperature treatments

method of treating foods with high temperature for short times

56

equivalent treatments

as temperature rises, less time is needed to kill same number of microbes

57

hot air sterilization

items are placed in an oven for longer period, higher temperature is required

58

filtration

passage of a liquid/gas through a screenlike material with pores small enough to retain microorganisms

59

high-effeciency particulate are filters

remove almost all microorganisms larger than about 0.3um in diameter

60

phenol

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phenol was used to control surgical infections in the operation room.

61

phenolics

derivative of phenol, contains a molecule of phenol that is chemically altered to reduce its irritation qualities and increase antibacterial activity

62

cresols

most frequently used phenolics

63

bisphenol

contain 2 phenolic groups, hexachlorophenes and triclosan

64

hexachlorophenes

is an ingredient of a prescription lotion, pHisoHex, used for surgical and hospital microbial control procedure

65

triclosan

is an antibacterial soap

66

what forms when chlorine is combined with water

hypochlorous acid

Cl2 + H2O <-> H+ + Cl- + HOCl

67

quaternary ammonium compounds

most used surface active agents

68

what is sodium hypochlorite used as

a household disinfectant and bleach

69

what is potassium sorbate and benzoate used for

to prevent molds from growing on acidic foods

70

what is calcium propionate used for

it is an effective fungistat used in bread

71

evaluation of disinfectants by the disk-dilution method

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