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microbiology 319 > chapter 13 > Flashcards

chapter 13 Flashcards

exam 3 microbial growth (58 cards)

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1
Q

how clean is clean

A

clean is a relative term
something clean may have microorganisms on it
how clean something is depends on the intended use of the object

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2
Q

why clean and not sterilize everything

A

Sterilization requires
time
labor intensive
may degrade the quality of the item being treated
have toxic effects on users

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3
Q

biosafety levels

A

ranked by the severity of the disease and ease of transmission

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4
Q

what are the biosafety levels

A

BSL1 through BSL 4
BSL 1 poses the least risk and BSL 4 poses the highest risk

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5
Q

bsl 1

A

Microbes are not known to cause disease in healthy hosts and pose minimal risk to workers and the environment
ex: nonpathogenic strains of Ecoli

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6
Q

bsl 2

A

microbes are indigenous and are associated with diseases of varying severity, pose a moderate risk to workers and the environment
ex: staphylococcus aureus

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7
Q

bsl 3

A

microbes are indigenous or exotic and cause serious or potentially lethal diseases through respiratorty transmission
ex: Mycobacterium tuberculosis

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8
Q

bsl 4

A

microbes are dangerous and exotic posing a high risk of aerosol-transmitted infections, which are frequently fatal without treatment or vaccines
ex: ebola and marburg virus

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9
Q

sterilization

A

process by which ALL living cells, spores and viruses are destroyed on an object

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10
Q

disinfection

A

The killing or removal of disease-producing organisms from inanimate objects
does not result in sterilization

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11
Q

anitsepsis

A

similar to disinfection but applies to removing pathogens from the surface of living tissues such as skin

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12
Q

sanitation

A

consists of reducing the microbial population to safe levels and usually involves cleaning an object as well as disinfection

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13
Q

cidal agents

A

kill microbes
ex: bactericidal or fungicidal

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14
Q

static agents

A

inhibit or control growth of microbes
ex: bacteriostatic or fungistatic

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15
Q

selection of disinfectant

A
  1. must be fast acting in the presence of organic materials
  2. must be effective against all microorganisms without destroying tissue or acting as a toxin if ingested
  3. easily penetrate material without discoloration or damage
  4. easy to prepare and stable in the environment of use
  5. inexpensive and easy to use
  6. not have an unpleasant odor
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16
Q

microbial death curve

A
  1. Evaluate the degree of microbial control
  2. when exposed to a particular microbial control protocol a fixed percentage of the microbes within the population will die
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17
Q

death curves are often plotted as

A

semilog plogs
reduction in microorganisms is typically logarithmic

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18
Q

decimal reduction time (D-value)

A

time it takes for microbial control protocol to kill 90% of the population

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19
Q

factors influencing speed of lethal damage

A
  1. initial pop. size (larger pop, longer time to decrease)
  2. population composition (are spores involved)
  3. Agent concentration or dose for radiation
  4. duration of exposure
  5. Presence of organic material that can inhibit disinfectant action
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20
Q

physical control measures of microbes

A

temperature extremes
pressure (coupled w temperature)
filtration
irradiation: process of exposing an object to radiation

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21
Q

is moist heat or dry heat more effective at killing microbes

A

moist heat is more effective

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22
Q

why is moist heat more effective

A

Denatures and coagulates proteins which are essential for microbial function

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23
Q

what does dry heat do

A

primary oxidizes proteins, requiring higher temperatures and longer exposure times

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24
Q

standard autoclave conditions

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A

121 °C at 15 psi (pounds per square inch)

25
what do we use autoclaves for
sterilize glassware and plasticware resistant to high temperature and pressure
26
12 D method
amount of time required to kill 10^12 spores or reduce the population by 12 logs in the food industry produces food that is safe
27
For what industry is 12D extremely important for
canning industry ensure that canned goods that are associated w strict anaerobes like Clostridium botulinum spores are not present
28
thermal death point (TDP)
lowest temperature that kills the bacteria in a 24 hour old culture in 10 minutes Time constant, temperature varies
29
thermal death time (TDT)
Time required to kill all bacteria in a culture at a specified temperature temperature constant but time varies
30
pasteurization
Goal is not to sterilize but to kill pathogens without affecting the texture, color, or taste of the product
31
What does pausterization involve
Heating a particular food like milk to a moderately high temperature long enough to kill Coxiella burnetti, which is the causative agent of Q fever and the most heat-resistant spore-forming pathogen known
32
Low temperature long time (LTLT)
temperature: 63 °C for 30 minutes
33
High temperature short time (HTST)
flash pasteurization temperature: 72 C for only 15 seconds
34
Ultra high temperature (UHT)
temperature: 138 °C for 2 seconds can produce sterilized products for unrefrigerated items with a shelf life of up to 6 months
35
low temperatures have 2 basic purposes in microbiology
temper growth preserve strains
36
what happens to bacteria in cold temperatures
grow more slowly but also die more slowly
37
refrigeration
about 4-8 °C decreases microbial activity but doesn't kill microorganisms
38
freezing
-20 C Microorganisms can be stored this way Long-term storage involves placing solutions in glycerol at very low temperatures (70 °C) Deep freezing suspends growth altogether and keeps cells from dying
39
freeze drying (lyophilization)
cultures are quickly frozen at very low temperatures and placed under a vacuum, which causes the water to sublimate cannot function without water so growth suspended
40
filtration
Solutions are sterilized by passing them through sterile filters with tiny pore sizes that effectively sift microbes out of the fluid filtration through micropore filters of 0.2 micrometers is effective for microbial cells but not for viruses
41
sonication
high frequency ultrasound waves to disrupt cell structure leads to cavitation: formation of bubbles inside the cell which disrupts cell structures and causes cell to lyse
42
sonication in lab
effectively lysing cells to release their contents for further research
43
sonication outside lab
cleaning surgical instruments lenses coins tools musical instruments
44
irradiation
method in which objects are bombarded with high energy electromagnetic radiation
45
what happens to food when irradiated
foods do not become radioactive when irradiated any reactive molecules produced when high energy particles are absorbed by food dissipate almost immediately
46
Ultraviolet light (UV)
UV light is useful only for surface sterilization due to its poor penetrating ability
47
how well chemical agents work depend on
The presence of organic matter The kinds of microorganisms present corrosiveness stability, odor, and surface tension
48
commercial disinfectants
ethanol, iodine, chlorine surfactants aldehydes phenolics heavy metals peroxygen
49
ethanol, iodine and chlorine
highly reactive compounds that damage proteins lipids and DNA
50
surfactants
such as detergents help in the mechanical removal of microbes from a surface
51
aldehydes
combine with and inactivate proteins and nucleic acids
52
phenolics
denature proteins and disrupt membranes sterilize surgical wounds
53
heavy metals
bind to proteins and inhibit enzymatic activity
54
peroxygen
Strong oxidizers, produce free radicals that damage cellular macromolecules
55
gas sterilization
Disposable plastic ware, such as petri dishes, syringes, sutures, and catheters, is not resistant to heat sterilization or chemical disinfectants. These types of products are best sterilized by gamma irradiation or antimicrobial gases, such as ethylene oxide (EtO)
56
key characteristics of gas sterilization
1. destroys proteins by alkylation 2.microbicidal/sporicidal 3. rapidly penetrates packing materials, including plastic wraps 4. highly explosive
57
Bacterial resistance to disinfectants
It is difficult for bacteria to develop resistance to chemical agents that have multiple targets and can easily diffuse into a cell
58
low concentration disinfectants
Disinfectants that have multiple targets at high concentrations may only have a single target at low concentrations can foster resistance

microbiology 319 (15 decks)

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