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BIO111: Microbiology > Chapter 5 > Flashcards

Flashcards in Chapter 5 Deck (91):
1

Sterilization

Process of destroying all microorganisms (including endospores) or viruses within or on a product.

2

Does sterilization remove prions

No, because they are hard to get rid of, heat-resistant, would need to be targeted individually

3

Sterilant

chemical that removes all microbes

4

Disinfection

Product that kills microorganisms or viruses within or on product, but SOME microbes may remain

5

Disinfectant

chemical used to destroy MOST microbes on an inanimate object

6

Types of Disinfectants

"cide" = treatments that kill
"static" = treatments that inhibit rather than kill

7

Germicide

a disinfectant that kills microorganisms & viruses

8

Bactericide

a disinfectant used to kill vegetative forms of bacteria, but not usually endospores

9

Fungicide

a disinfectant used to kill fungus

10

Virucide

a disinfectant used to kill viruses

11

Bacteriostatic or fungistatic agent

chemical or condition that prevents growth of bacteria/fungus, but does not kill them

12

Antiseptic

Chemical that is non-toxic enough to be used on human tissue
- Used for cleaning skin surfaces, such as hands and wounds, and as prep for surgery
-Kills or decreases microbes
-Does not destroy endospores

13

Decontamination

- process that reduces the number of microbes to a safe level
- may kill, inactivate or remove microorganism, viruses and any toxins that may be present within or on the product
- important in the food industry, decontamination of an area or product to meet public health standards

14

Sanitizer

chemical used to decontaminate.

15

Factors relating to antimicrobial action

Time of contact
# of microbes
Temperature/pH
D value
Chemical concentration
Type of microbe
Extraneous materials

16

Time of Contact

- Death of microbe is not always instantaneous
- Only a fraction of microbes are killed in a certain period of time
- May take 12 or more hours to destroy most or all of the bacteria growing on an object

17

Number of microbes

- Death of a population of bacteria is related to the number of cells present
- The greater the number of cells on a surface, the greater amount of time is needed to disinfect that surface

18

D value

Decimal reduction time
= time to kill 90% of bacteria present
- D value is usually constant

19

D value example

if D= 2 minutes, then a population of 100 would be reduced to 10 in 2 minutes and to 1 in 4 minutes.
Shows the time of contact and number of microbes affect the action of the disinfectant

20

Temperature and pH

- Chemical disinfectants usually work better at higher temperatures
- most disinfectants are designed to work near room temp.
- disinfectants also have optimum pH range, but this varies for chemical type
- If temperature of pH is not optimum, the time of contact must be increased

21

Concentration of Chemical disinfectant

- Mostly, more concentrated disinfectant = shorter killing time
- at lower concentration are bacteriostatic
- at higher concentration are bactericidal

22

Types of microbes

Least resistance
Moderate resistance
Highest resistance

23

Least resistance microbes

vegetative forms of most bacteria and viruses with membranes

24

Moderate resistance microbes

- Mycobacterium tuberculosis
- Staphylococcus aureus
-Pseudomonas species
-Naked viruses

25

Mycobacterium tuberculosis facts

Acid fast positive d/t mycolic acid in cell wall being stained by phenol

26

staphylococcus aureus facts

clumping factor, capsule, Gram -

27

Pseudomonas species facts

Gram -, biofilms, low nutrition requirements

28

Highest resistance microbes

Bacterial endospores
(Clostridium and bacillus)

29

Why are endospores so hard to kill

dipcolenic acid to keep moisture away from DNA in endospore. Super resistant to heat and chemicals.
Peptidoglycan helps protect as well

30

Presence of extraneous matter

- Soil, blood, pus
- organic matter may react with disinfectant and cause them to be less effective
- Therefore recommended to clean surface before using disinfectant

31

Effectiveness of microbial control

High effectiveness
Intermediate effectiveness
Low effectiveness

32

High effectiveness

kills ALL organisms including endospores. Sterilization!

33

Intermediate effectiveness

kills "moderate resistant" pathogens
ex. mycobacterium tuberculosis, staph aureus, pseudomonas, naked viruses

34

Low effectiveness

kills vegetative bacteria and enveloped viruses

35

Mode of Action

- Adverse effect on microbe - how it kills or harms
- some methods of microbial control are general and destroy or alter many structures
- some methods are very specific to certain portion of bacterial cell or virus
- Targets: synthesis and structure of cell, cell membrane, proteins, and nucleic acid

36

Cell wall and cell membrane
(mode of action target)

- Synthesis of cell wall disrupted or cell wall is digested after it is synthesized. Weak cell wall exposes microbe to environment and can lead to lysing.
-Cell membrane damaged so it is "leaky" (no longer selectively permeable)
- molecules can enter and exit cell easily

37

Proteins
(mode of action target)

-Synthesis of proteins stopped when antimicrobial agent...
1. binds to ribosome - prevents translation
2. binds to DNA - prevents transcription
- protein function altered when antimicrobial agent binds to protein and alters protein shape (denaturation)
- So also affects metabolic processes if enzymes are target

38

Nucleic Acids
(mode of action target)

- DNA synthesis may be stopped when antimicrobial agent causes mutations. ex. Thiamine dimers
- If DNA synthesis is affected then protein synthesis may also be affected

39

3 possible outcomes of mutations

- Beneficial
- Death
- Unchanged or no change

40

Chemical methods of microbial control

- Over 10,000 types of chemical control.
- Different types used in hospital: Alcohol, Hydrogen peroxide, Surfactants, Heavy metals, Phenol (carbolic acid), ethylene oxide, chlorine and iodine

41

effectiveness of ALCOHOL

-Low effectiveness

42

Action of ALCOHOL

disrupts cell membranes, denatures cellular proteins, do not destroy endospores

43

Concentration of ALCOHOL

exception: should be diluted to 75% to dissolve proteins first

44

Contact time of ALCOHOL

limited because of quick evaporation

45

Types of ALCOHOL and toxicity to humans

-Ethyl (ethanol, grain) - non-toxic- more expensive (hand sanitizer)
- Isopropanol (rubbing) - more effective, but more toxic to animals - vapors can cause damage to CNS

46

HYDROGEN PEROXIDE effectiveness

low

47

Toxicity of HYDROGEN PEROXIDE to humans

None

48

Action of HYDROGEN PEROXIDE

large amounts overwhelm catalase and peroxidase in cell

49

Surfactants

surface-active agents, detergents = reduce surface tension of water and allow organics to dissolve easily

50

Anionic (soap)
action and effectiveness

does not kill ("no effectiveness") but removes microbes. Creates micelle, surrounding dirt

51

Cationic (quaternary ammonium compounds or quats)
action and effectiveness

- low effectiveness (ineffective for Gram - bacteria)
- ADBAC
-

52

Toxicity of surfactants to humans

low to none

53

pH of cationic vs anionic

Cationic = basic
anionic = acidic

54

Heavy metals

Mercury - metaphen/nitromersol
Silver - silver nitrate (newborns now given erythromycin), silver sulfasiazine (for burns)
Effectiveness - low

55

Toxicity of heavy metals to humans

toxic if used on exposed tissue, so used only topically ("topical antiseptic")

56

Action of heavy metals

denatures proteins, binds to sulfur containing proteins

57

Phenol and derivatives effectiveness

intermediate, often ineffective against naked viruses

58

phenol and derivatives toxicity

very toxic, used at topical antiseptic, dilute forms used in Lysol, triclosan

59

action of phenol and derivatives

damages cell membranes, denatures enzymes

60

Who used phenol as one of the first disinfectants

Lister

61

Ethylene Oxide effectiveness

High (endospores and viruses)

62

Toxicity of Ethylene oxide

high, carcinogen

63

Action of Ethylene oxide

- usually in gas form, explosive
- slow acting (up to 18 hours in special chamber)
- used for heat or moisture sensitive items
-mutagen, requires aeration of product before use

64

Effectiveness of chlorine and iodine

intermediate

65

Toxicity to humans of chlorine and iodine

slightly toxic, irritating to tissues, possible carcinogen

66

Action of chlorine and iodine

denatures proteins and DNA

67

iodine combined with alcohol is called

tincture

68

iodine + detergent =

iodophore
less irritating and do not stain, can be contaminated with Pseudomonas species

69

Bleach

sodium hypochlorite

70

Hand cleansing soap and water

removes extraneous matter and microorganisms

71

Hand cleansing with antibacterial soap

triclosan (contains phenol)

72

Hand cleansing with hand sanitizers

alcohol

73

Physical methods of microbial control

-Dry heat
-Moist heat
- Autoclave
- Harvey chemiclave
-Radiation - UV and ionizing
- Filtration

74

Dry Heat

- incineration of contaminant in hot oven or direct flame
- Bunsen burner
-Sterilize glassware, powders, oil

75

Disadvantage of dry heat

time - destruction of endospores would require 150-180 C for 2-4 hrs, which would burn up most materials

76

Moist heat

- boiling or steaming kills vegetative forms, denatures proteins
- boiling water = 100C

77

Disadvantages of moist heat

-some microbes can tolerate short boiling times
- endospores survive several hours of boiling
- Greatly reduces number of bacteria, but does not sterilize

78

pasteurization

Flash method
Holding method
Ultra

79

Flash method
(pasteurization)

high temp (72C) for short time (15 seconds) as liquid is in pipes is common method

80

Holding method
(pasteurization)

lower temp (63C) for longer time (30 mins) - treated in bulk

81

Ultra
(pasteurization)

high temp (140) for shorter time ( a few seconds)

82

Autoclave

moist heat under pressure
- when water is present, all macromolecules are denatures at relatively low temperatures
- Steam under 15 psi pressure can reach temperature of 121C which will kill even endospores after 15 minutes

83

Disadvantage of autoclave

some items can be damaged by water and heat

84

Harvey Chemiclave

-Alcohol or formaldehyde vapor is pressurized and heated
- used for dental instruments

85

disadvantages of Harvey Chemiclave

more expensive that autoclave, but does not require drying time
-Some items can be damaged by chemicals, heat or pressure

86

UV radiation

- changes to DNA structure (thyamine dimers) = mutations
- bacteria can repair unless high doses of UV used
- Reduced microbes to 99% (disinfectant)
- very effective against actively reproducing cells but not endospores because of mutations

87

Disadvantages of UV radiation

stopped by solids: used on air, some liquids & surfaces
- also damages human tissue

88

Ionizing radiation

x-rays and Gamma rays - very high energy wavelengths
- remove electrons: breaks DNA and cell membrane
- Used in food preparation and in some hospital settings
- can penetrate most solids - fabric, plastic, food
- Gram - bacteria very susceptible

89

Disadvantages of ionizing radiation

- not effective on endospores
- damages human tissue

90

filtration

- filters with pores from 0.02 - 8 micrometers
- will filter our bacteria and some viruses
- good for heat sensitive fluids (beer, wine)
- Air filtration used in sterile environments (OR)

91

Disadvantage of filtration

- does not capture small viruses or toxins
- does not destroy microbes