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BIO233 > Controlling Microbial Growth > Flashcards

Controlling Microbial Growth Flashcards

1
Q

Heat and radiation are examples of what kidn of control method

A

Physical agents

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2
Q

Sterilzation and disnifection are what kind of control method

A

(gas) chemical agents

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3
Q

Filtration is a kind of

A

Mecahnical removal m=of microbes

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4
Q

Sterilization

A

Destruction/removal of all forms of microbial life from and object

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5
Q

Physical processes of sterilization

A

Filtration
High temp
Incineration
Irradiation by UV or gamma rays

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6
Q

Chemical processes of sterilization

A

Ethylene oxide (used in hospitals)
Chlorine dioxide (decontamination of buildings)
Steam sterilization (microbiology)

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7
Q

Mechanical processes of sterilization

A

filtration

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8
Q

Disinfection

A

Broad defintion
includes sanitization and antisepsis

Use of chemicals (disinfectants) to kill or inhibit microorganisms that cause disease

Does not kill all microorganisms
Usually toxic and injurious to human tissues

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9
Q

Widely use Chemicals disinfectants:

A

Chlorine (water supplies)
Phenols,
Biphenols (chlorhexidine),
Alcohols
Iodine
Aldehydes
Quats (quaternary ammonium salts)
Ozone and UV light (newer means)

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10
Q

Sanitization

A

Related to disinfection, but sanitization only reduces the microbial population to acceptable standards.
Restaurants/cafeterias sanitize eating utensils to acceptable public health standards.

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11
Q

Antisepsis

A

Related to disinfection, but used on living tissues
Chemicals used to treat or prevent infection of living tissues (still toxic)
Ex.
Alcohol
Iodine
Chlorhexidine
Heavy metals

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12
Q

Antimicrobial agents

A

Agents that kill or inhibit the growth of microorganisms (cidal or static)

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13
Q

Cide

A

suffix indicating agent kills organisms

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14
Q

Biocide or germicide kills

A

Kill microorganisms

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15
Q

Virocide

A

Inacivates viruses

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16
Q

Static

A

agent that inhibit growth
Bacteriostatic agent: (inhibits) growth of bacteria

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17
Q

Sepsis

A

Bacterial contamination

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18
Q

Aesepsis

A

Absence of significant contamination

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19
Q

Aseptic techniques

A

Methods that minimizes contamination

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20
Q

Factors affecting antimicrobial effectiveness

A

Population size: Large the population (Of microorganisms) = Longer to kill

Population composition: Different sensitivity to antimicrobials

Concentration or intensity: Higher conc, = greater effect
EXCEPT alcohol 70% is more effective than 100%
Time of exposure: Longer exposure = more organisms killed

Environmental conditions
High tem (more killing)
Organic material (decreased killing)
Sewage (reduce effeeiveness of disinfectants), biofilms
Microbial chaaraceristics: Spores more resistant than vegetative cells

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21
Q

Is Gram - or Gram + more resistant

A

Gram - more resistant than Gram + bacteria

Most antimicrobial agents tend to be water soluble, therefore, they cannot easily cross plasma membranes SO Gram - outer layer keeps them out
Pseudomonas aeruginosa - MOST resistant Gram - (Affects burn victims and causes Cystic fibrosis)
Cystic Fibrosis: Protein in mucous layer doesn’t function effectively, therefore mucous layer in respiratory tract becomes thick

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22
Q

Acid-fast or non acid fast more resistant

A

Acid-fast more resistant than non-acid fast

Mycobacterium TB - Resistant to aqueous baceticide bc mycolic acid layer

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23
Q

Endospores more resistant than vegetative

A

Endospores MOST resistant bacteria forms

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24
Q

Naked Viruses or Enveloped viruses more resistant

A

Envolope (if envelope is broken virus dies) viruses tend to be very easy to destroy (when outside the body)
Naked ones have thick protein coats which protects
Covid is a virus with a lipid envolope

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25
Q

Cyst or trophozoite protozoans more resistant?

A

Cysts (surival structure for eukaryotic organisms) resistant to chlorine in water
–Cryptosporidium cysts resistant to chlorine in water (spread by pigeons)

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26
Q

How quickly and at what rate do bacteria die off?

A

Bacteria die at constant rate
The higher the conc. the longer it takes

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27
Q

Most resistant to least resistant forms of microorganisms

A

Prions
Endospores of bacteri
Mycobacteria
Cysts of protozoa
Vegetative protozoa
Gram-negative bacteria
Fungi AND fungal spores
Viruses without envolopes
Gram-positive bacteria
Viruses with lipid envolopes

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28
Q

Most common physical control method

A

Heat

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29
Q

Why is moist heat more effective

A

Moist heat is more effective (steam at 100C more dangerous than oven at 325C)

Moist heat
Kills by coagulation of protein

Boiling water does not actually reach as high heat

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30
Q

How does dry heat kill microbes

A

By oxidation (requires high temps for a longer time)

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31
Q

Approx. conditions for moist heat killing

A

Yeast is the lowest temperature for 5 mintes

Molds is a higher temperature for 30 minutes
Bacteria is the highest temperature for 10 minutes

But endospores must be boiled for up to 20 hours to kill them

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32
Q

Does pasteurization change the tast

A

No

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33
Q

What bacteria is milk

A

Mycobacterium tuberculosis

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34
Q

3 levels of pastuerization

A

Low-temperature hold (LTH)
62.8°C for 30 minutes
High-temperature short-term (HTST):
72°C for 15 seconds
Ultra-high temperature (UHT):
Process (5 sec cycle 74oC 140°C  74oC)

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35
Q

Autoclave

A

Saturated chamber with steam
Raise temp to 121oC
Apply pressure: 15 psi for 15 min
Steam condenses on objects (121oC)

Lower pressure to normal before opening chamber
For surgical instruments, chamber is opened before pressure falls for solid objects (surgica instruments) to dry them instantly

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36
Q

3 forms of dry heat

A

Incineration
Flaming
Oven (170°C, 2 hours)

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37
Q

Two types of mechanical filtration

A

Depth filtering
Membrane filters

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38
Q

How small do mechanical porte sizes go

A

.2 micrometers

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39
Q

What does bacteriostatic mean

A

most pathogens cannot grow

i.e. refridgeration

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40
Q

A bacteria that is an exception to refridgeration being bacteriostatic

A

Listeria moncyotgenes

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41
Q

What is non ionizing radiation

A

UV light

Non penetrating
Can damage eyes, DNA
Germicidal lamps for vaccine disinfection

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42
Q

What is ionizing radiation

A

Gamma rays, X ays, or high energy electron beams

Cause mutation and death
Low level ioninzing radiation > Used on speices certain meats and vegetables

High energy radiation > used to sterilize medical supplies

43
Q

How is “limiting water” applied to creating a bacteriostatic environment

A

Bacteria need water to survive

High concentration of salt and sugar in solutions creates a hypertonic environment and thus bacteriostatic

44
Q

Which kinds of microorganisms most resistant to desiccation and high salt conc.?

A

Molds and yeasts

45
Q

How are disinfectants evaluated?

A

By the disc dilution method

Inoculate bacteria on nutrient agar plates

Place filter discs impregnated with disinfectant on plates and incubate

Measure zones of inhibition
(diameter) to determine effectiveness, larger diameter, greater effectiveness

46
Q

What type of chemical disinfectant is used in lysol, toothpaste, and is an excellent skin disinfectant with a broad spectrum of activity?

A

Phenols

47
Q

What disinfectant is used by desntists, having a low toxicity and thus safe for skin and mucous membranes

A

Chlorhexidine

48
Q

What are the major examples of halogens

A

Iodine
Chlorine
Chlorine gas
chloramines

49
Q

Who was the pioneer of phenols

A

Joseph Lister

50
Q

What is an Effectant chemical disinfectant against S. aureus

A

Hexachlorophene
(phenol)

51
Q

What “chemicals” are used for cleaning prior to surgeyr

A

Alcohols

52
Q

widely used alchol disinfectant

A

Ethanol or isopropanol

53
Q

Alcohol is most afffective at what level

A

70% aqueous solution

54
Q

How do heavy metals affect microbes?

A

Denature proteins

55
Q

What are examples of surfactants

A

Soaps, detergents
- Clean but minimal disinfectant

56
Q

Quat

A

Quaternary Ammonim compounds

57
Q

What are quats commonly used in

A

Mouth wash

Germicidal against most pathogens but not endospores

58
Q

What kind of bacteria is mouthwash most effective against

A

Gram +

59
Q

Hydrogen peroxide is classified as

A

An oxidizing agent
Under the category of chemical sterilization

60
Q

What do hospitals use as a chemical sterilant for bedding and mattresses

A

Ethylene oxide

61
Q

Chlorine Dioxide

A

Used to sterilize building and contents of endospores or anthrax

Also used in water treatment

62
Q

How do oxidizing agents affect microbes

A

Interfere with metabolism

63
Q

Ozone category and use

A

An oxidizing agent used as a primary water disinfectant

64
Q

Why is a log curve used to graph bacteria death rates

A

Using a logarithmic scale makes it easier to visualize the population changes at late time points—the same data points that would otherwise be compressed down against the x-axis.

65
Q

What can lead to C diff

A

Overuse of antibiotics

66
Q

What do Healthcare facillities use for a higher level disinfectant than quats

A

Hypocholorite disinfectants

67
Q

Disinfectant vs antiseptic

A

Disinfectant
Use of chemicals (disinfectants) to kill or inhibit microorganisms that cause disease

Does not kill all microorganisms
Usually toxic and injurious to human tissues

Antispectic: Chemicals used to treat or prevent infection of living tissues (still toxic)

68
Q

Is heating food in the microwave microbial control?

A

NO

69
Q

Does lightly heating food kill microbes?

A

No

70
Q

Disinfectant used for skin?

A

No, that’s antiseptic

71
Q

Least susceptible microbes to sterilization

A

prions

72
Q

Does dry heat OR pasteurization sterilize

A

Only dry heat sterilizes

73
Q

Which of the following is a limitation of the autoclave?

A

cannot be used for heat labile materials

74
Q

Which of the following treatments is the most effective for controlling microbial growth?

A

140°C for 4 seconds

75
Q

Chlorhexidine use

A

for skin antisepsis but not for disinfection of environmental surfaces

76
Q

microbes is known to be the most resistant to quaternary ammonium compounds?

A

Members of the genus Pseudomonas

77
Q

Does alcohol sterilize

A

No

78
Q

What bacteria is not effected by quats

A

Pseudomonas auriginos

Can grow in quats

79
Q

Semicritical instruments

A

Contact mucous Membrane and non intact skin

80
Q

C. diff

A

Gram positive bacteria

81
Q

Symptoms of C. diff

A

Digestive and colon problems

82
Q

How must C. diff be disinfected

A

Quats cannot be used, but hypocolrite (Chlorine) based disinfectants used on surfaces that might come in contact with fecal matter

83
Q

Spaulding rules

A

Critical (surgical instruments), semicritical, noncritical

84
Q

Free radicals

A

Free floating electrons that damage membrane structure, DNA

  • Very reactive
85
Q

What chemical keeps the steaks fresh

A

Sodium nitrate and nitrite

86
Q

3 things contributing to HAI

A

Presence of microorganisms
Immunocompromised individuals
Chain of transmission (people, bedding, equipment)

87
Q

What do surfactants do

A

Decrease surface tension or damage lipid membrane

88
Q

Purpose of soaps

A

for cleaning but little disinfectant

89
Q

Why is a 70% ethanol solution more effective than 100%

A

70% aqueous solutions more effective than 100% alcoholic solutions
Pure ethanol evaporates very quickly
Pure ethanol would cross the momebrane very quickly and react with proteins in the outer cytoplasm (TOO QUICKLY), forming a crust of dead proteins, protecting the cell from further ethanol exposure
70% ethanol reduces effectiveness, slows denaturing process, so no crust forms and more damage done to cell

90
Q

Is ethanol effective against viruses?

A

Yes

ALSO effective on lipid envelope and protein envelope (naked) viruses

91
Q

How is mercury used medicinially

A

This heavy metal is found in eye drops and in contact lens solutions

92
Q

What kinds of bacteria are quats effective against

A

G+

Not effective against endospores or mycobacteria

93
Q

Ethyline oxide

A

(Penetrates deeper than liquid alcohol)
Denatures protein
High penetration power
Sterilizes *microbes AND spores (Requires lengthy exposure time)
Used ikn hospitals as chemical sterilant (beddings, mattressses)

94
Q

Sodium nitrate and nitrite use for people

A

Keeping steaks fresh

95
Q

Cleaning a toilet bowl would be considered __________

A

Disinfecting

96
Q

Do autoclaves sterilize?

A

Yes

97
Q

How could dairy products avoid requiring refrigeration?

A

Ultra-high-temperature (UHT) treatment

98
Q

Which parts of the cell are the major targets of antimicrobial agents?

A

Proteins and cell membranes

99
Q

why are microbial death curves are typically plotted logarithmically

A

Most microbial death occurs in the begining

100
Q

Strategies for microbial growth control for heat labile items?

A

Filtration (for liquids not gases)
Non Ionizing radiation
Dessication
Ossmotic pressure

101
Q

How do phenyls afffect microbial growth>

A

Phenolics exert antimicrobial activity by injuring lipid-containing plasma membranes, which causes the cellular components to leak out of the cell

102
Q

What phase in bacterial growth is penicillin most effective

A

Log

103
Q

Most effective form of microbial growth control

A

UHT (5 sec cycle 74oC 140°C  74oC)

104
Q
A

BIO233 (18 decks)

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