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Microbiology Exam 2 > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

Name some mechanical physical methods of controlling microorganisms

A

scrubbing
germicidal soap (alcohol scrubs)
filtration
sedimentation

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2
Q

What is the difference between bland soap and germicidal soap?

A

bland soap reduces the number of bacteria, but they are still able to multiply. It also lowers the surface tension (emulsifier/surfactant)
germicidal soaps have residual action

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2
Q

What is residual action?

A

germicidal soap contains a chemical that sticks to skin and continues to work at killing bacteria

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3
Q

Which is better according to the CDC:

non-germicidal (bland) soap OR germicidal soap (alcohol scrubs)?

A

They are both equals as far as routine hand-washing

the bland soap is best to use if hands are visibly dirty

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4
Q

What is filtration?

A

Passing a liquid or gas through a membrane filter to remove microorganisms
the filter is made out of cellulose (paper)
Is best for heat labile things

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5
Q

What is a screen hole size of .45 micro meters good for filtering?

A

Will filter out large prokaryotes and yeast

NOT mycoplasma and other small prokaryotes

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6
Q

What is a screen hole size of .2 micro meters good for filtering?

A

Will filter out all prokaryotic cells

MISSES viruses

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7
Q

Does a .2 micro meter screen hole sized filter sterilize a solution?

A

yes, officially

although viruses will still be able to pass through

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8
Q

What is the largest screen hole sized filter which all viruses will be removed?

A

0.02 micro meters

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9
Q

Why don’t we use 0.01 micro meter screen hole sized filters as the gold standard?

A

they can easily clog up which prolongs the filtration process

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10
Q

What is sedimentation used for?

A

water treatment such as the sewer system and septic tanks

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11
Q

What is the mode of action of sedimentation?

A

suspended particles which eventually settle

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12
Q

What is the process of water treatment?

A

first sedimentation
then filtration using rocks or soil
finally (in the city ONLY) chlorination

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13
Q

What chemical can be added to increase sedimentation in a septic tank?

A

ferric sulfate

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14
Q

Name 4 environmental conditions which can be used to control microorganisms

A

dessication
cold temperatures
osmotic pressure
sunlight

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15
Q

What is dessication? why is it effective against microorganisms?

A

drying out

it removes water necessary for enzymatic hydrolysis

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16
Q

How long can Hepatitis B survive in a dry environment?

A

at least 7 days

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17
Q

How long can TB survive in a dry environment?

A

8 months because of its waxy coat

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18
Q

How long can Syphilis survive in a dry environment?

A

minutes

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19
Q

How long can Gonorrhea survive in a dry environment?

A

hours

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20
Q

How long can Salmonella survive in a dry environment?

A

2 months

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21
Q

How long can spores survive in a dry environment?

A

indefinetly

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22
Q

How long can E. coli survive in a dry environment?

A

2 months

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23
Q

How long can HIV AIDS survive in a dry environment?

A

6 hours outside the body on a dry surface

1.5 days inside cells such as semen and pus

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24
How long can Staphylococcus aureus survive in a dry environment?
2 months
25
What is the relationship between dessication of microorganisms and the food we eat?
when mixing dry foods (such as cereal) with wet foods (such as milk), eat immediately because bacteria may be static due to dessication and adding liquid will reactivate their growth
26
Which organism is found in cereals and can become harmful when the cereal gets wet?
Staph aureus
27
Which organism is found in dried eggs?
Salmonella (of course dummie :P )
28
Dessication can have an effect on these types of yeast: | ________________
athletes foot and yeast infections | they thrive in moist environments
29
Freezing is cidal to what kinds of organisms? It is NOT cidal to what kinds of organisms
eukaryotic cells | it is NOT cidal to bacteria
30
What does the freezer do to eukaryotic cells?
frozen water forms crystals which can puncture cell walls
31
What does the freezer do to bacteria?
it removes the water necessary for enzymatic reactions | the bacterial population does not grow (becomes static)
32
What does the refrigerator do to bacteria?
slows the rate of enzymatic reaction but does NOT stop it | Bacteria will continue to grow slowly
33
Name 2 mediums which can be used to control microorganism populations via osmotic pressure
brine and sugar solutions
34
What happen to bacteria in a hypertonic environment?
they undergo plasmolysis
35
What grows in brine and is it a problem?
only halophiles will grow but they are non pathogenic
36
What grows in high sugar solutions and is it a problem?
saccharophilic organisms such as mold will grow in up to 70% sugar solution but they are non pathogenic
37
What is a high sugar solution used for?
preservation of fruit (would make jams and jellies)
38
What is the mode of action of sunlight as a form of microorganism control?
photo oxidation (of proteins)
39
How long can mycobacterium TB last with dessication? with dessication AND sunlight?
8 month in dessication | a few days in the sun
40
Name different types of radiation
``` UV Infrared microwaves gamma rays cathode rays x rays ```
41
what is the mode of action of radiation?
destroys DNA
42
Is radiation efffective against prions? why or why not?
no because prions only have RNA
43
Is UV penetrative?
no | this is why sunblock is effective
44
What can UV light do to seratia narcescens?
it can be mutated to only be white and never change back to red using laminar flow hoods
45
Does UV light sterilize or disinfect?
disinfect
46
Can UV light be used for water purification?
yes | BUT the water has to be very clean to begin with
47
Does UV light work on spores?
yes
48
What is the mode of action of UV light?
makes DNA form pyrimidine dimers (cytosine and thymine begin forming bonds with themselves instead of the normal AT and CG bonds) this breaks hydrogen bonds and forms mutations
49
Are infrared light and microwaves sterilizing or disinfecting?
disinfecting
50
What can infrared light and microwaves be used on to control microorganisms?
can be used for the disinfection of soft contact lenses and urinary catheters
51
What is the mode of action of infrared light and microwaves?
non-ionizing wavelengths get absorbed and given off as heat if the organism is dry, it is protein oxidation if it is wet, then it is protein coagulation
52
Are gamma rays penetrating?
yes, very | except for lead
53
where do gamma rays come from?
radioactive isotopes such as cobalt 60
54
what are gamma rays used for? why?
sterilizing bacon and produce | to gain a longer shelf life
55
do gamma rays deposit radioactive materials in meat?
no
56
What are cathode rays? What are they used for?
electron beams of high intensity | sterilization of sutures
57
Do cathode rays sterilize or disinfect?
sterilization of sutures
58
Are X-rays penetrating?
yes of course
59
Are X-rays dangerous?
they are too dangerous for routine use
60
What forms of radiation are ionizing?
gamma rays cathode rays x-rays
61
What is the mode of action of ionizing radiation?
uses ionizing energy to create hyperactive ions | ions strike DNA causing mutation
62
Can you use ionizing radiation for sterilization or disinfection?
While it could be used for sterilization, the FDA won't clear a high enough dose due to safety concerns therefore they are only used for disinfection in the USA

Microbiology Exam 2 (11 decks)

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