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Bacteriology > control of bacterial growth > Flashcards

control of bacterial growth Flashcards

1
Q

define sterilization

A

complete killing of all living microbes including spores

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2
Q

define contamination

A

treatment of objects or surfaces to make them safe to handle

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3
Q

define disinfection

A

control of pathogens on inanimate objects

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4
Q

define antisepsis

A

control of pathogens in living tissues

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5
Q

define sanitization

A

process to lower microbial loads

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6
Q

define ‘cidal’ biocides or germicides

A

they kill microbes

  • bactericide (bacteriocide)
  • fungicide
  • viricide
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7
Q

define ‘static’

A

they do not kill microbes but inhibit growth

  • bacteriostat
  • fungistat
  • -viristat
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8
Q

define sepsis

A

bacterial contamination

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9
Q

define asepsis

A

absence of bacterial contamination

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10
Q

what are some of the factors influencing the effectiveness?

A
  • # of mirobes
  • environmental conditions
  • time of exposure
  • microbial characteristics
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11
Q

define the mode of action: alteration of membrane permeability

A

leaks cellular contents

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12
Q

define the mode of action: damage to proteins

A

denaturation

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13
Q

define the mode of action: damage to nucleic acids

A

damaged DNA or RNA will interfere with cell division and protein synthesis

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14
Q

what are 3 physical ways to kill bacteria

A
  • heat
  • radiation
  • filtration
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15
Q

what is the most common method to kill bacteria?

A

heat

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16
Q

what does heat do to bacteria?

A

denatures proteins

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17
Q

what is the thermal death point?

A

the lowest temp at which all microbes in a particular suspension will be killed in 10 min

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18
Q

what is moist heat?

A

boiling at 100 C (10-15 min)

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19
Q

does moist heat kill spores?

A

no

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20
Q

what is steam under pressure (autoclave)

A

steam at 15 psi raises temp to 121 C

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21
Q

does autoclave kill spores?

A

yes

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22
Q

how do you know if the autoclave is done?

A

autoclaving tape

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23
Q

what is pasteurization?

A

0heat sensitive liquids( milk, fruit jiuce, etc)

  • intended to kill pathogens
  • lowers bacterial numbers and prolongs shelf life
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24
Q

how do you pasteurize something?

A

high-temp, short time (HTST)

72 C for 15 sec

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25
Q

how do you do ultra-high temp pasteurization?

A

milk is heated to 140 for 3 sec

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26
Q

is dry heat as effective as moist heat?

A

no

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27
Q

what is flaming?

A

sterilization of inoculating loops

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28
Q

what is incineration

A

contaminated materials and carcasses

29
Q

what is hot-air sterilization?

A

heating at 170 C for 2 hours

-used for glass wares

30
Q

what is radiation?

A

electromagnetic waves: microwaves, Xrays, gamma rays, etc

  • ionizing
  • nonionizing
31
Q

what is ionizing radiation?

A

wavelength

32
Q

what is nonionizing radiation?

A
  • wavelength >nm
  • UV rays
  • damages DNA by causing bonds to form between thymine (thymine dimers)
33
Q

do microwaves have much antimicrobial activity?

A

no, other than the effect of heat generated

34
Q

what is filtration?

A

sterilize heat sensitive liquids

  • membrane filters used to exclude bacteria
  • High efficiency particulate air (HEPA) filters are used in hospitals and labs
35
Q

what was the first chemical used as a disinfectant?

A

phenol

36
Q

what do we use now instead of phenol?

A

phenolics (derived from phenol, less irritant and more effective)

37
Q

what is the mode of action of phenol and phenolics?

A

disruption of cytoplasmic membrane

38
Q

what chemical is used as a standard to measure the effectiveness of all disinfectants?

A

phenol

39
Q

what are the standard organisms used as standards for testing disinfectants?

A

salmonella typhi and staphylococcus aureus

40
Q

what is the chart for phenol coefficient

A 
1 = same as phenol
>1 = more effective
41
Q

what compounds are halogens?

A

iodine and chlorine

-effective antimicrobial compounds

42
Q

what is one of the oldest and most effective antiseptics?

A

iodine

43
Q

what is tincture of iodine?

A

iodine in aqueous alcohol

44
Q

what is iodophore?

A

iodine complexed with an organic molecule for slow release (betadine)

45
Q

what happens to chlorine in water?

A

becomes hypochlorus acid (HOCl), which is a strong oxidizing agent

46
Q

what do alcohols kill?

A

people… and vegetative cells, but not the spores

47
Q

What is the mode of action of alcohol?

A

denature proteins and disrupts cytoplasmic membrane by dissolving lipid

48
Q

which is more effective, isopropanol or ehtanol?

A

isopropanol

49
Q

what heavy metals are disinfectants?

A

silver, mercury, copper and zinc

50
Q

what heavy metal is used as an algaecide in water troughs?

A

copper sulfate

51
Q

what heavy metal is used in foot baths?

A

zinc chloride

52
Q

what are surfactants?

A

surface active compounds

-soaps and detergents

53
Q

how do soaps work?

A

-no antiseptic action, but mechanically remove bacteria due to scrubbing

54
Q

what are used in cleaning dairy utensils and equipments?

A

acid-anionic surface active compounds

55
Q

what are quaternary ammonium compounds?

A

cationic detergents

  • more effective against gram +
  • no effect on spores
56
Q

benzalalkonium chloride and cetylpyridinium chloride are what?

A

quaternary ammonium compounds

57
Q

what are some oxidizing agents?

A

-ozonem hydrogen peroxide, benzyl peroxide and peracetic acid

58
Q

what is ozone used for?

A

disinfecting water

59
Q

why is hydrogen peroxide not useful in infected open wounds

A

it is rapidly broken down to water and o2 by catalase

60
Q

where is hydrogen peroxide useful?

A

in deep wounds caused by anaerobes because released o@ would kill them

61
Q

when is benzoyl peroxide useful?

A

in treating wounds infected by anaerobic bacteria

62
Q

what does peracetic acid kill?

A

spores

63
Q

what is used in the food processing industry and in disinfection of medical equipment?

A

Peracetic

64
Q

what are aldehyde’s mode of action?

A

inactivate proteins by forming covalent bonds with amino acids

65
Q

what is formalin used for?

A

to inactivate bacteria and toxins in vaccine preparation

66
Q

what is glutaraldehyde used for?

A

bactericidal and sporicidal

67
Q

what is ethlene oxide used for?

A
  • gaseous sterilizers

- effective against all microbes and spores but requires several hours

68
Q

what is the mode of action of ethylene oxide

A

denatures proteins

69
Q

what is ethylene oxide used for?

A

sterilizing medical equipments

-suspected carcinogen

Bacteriology (17 decks)

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