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Microbiology Exam 2 > Lecture 14 > Flashcards

Lecture 14 Flashcards

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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
Q

How long can Staphylococcus aureus survive in a dry environment?

A

2 months

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25
Q

What is the relationship between dessication of microorganisms and the food we eat?

A

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
Q

Which organism is found in cereals and can become harmful when the cereal gets wet?

A

Staph aureus

27
Q

Which organism is found in dried eggs?

A

Salmonella (of course dummie :P )

28
Q

Dessication can have an effect on these types of yeast:

________________

A

athletes foot and yeast infections

they thrive in moist environments

29
Q

Freezing is cidal to what kinds of organisms? It is NOT cidal to what kinds of organisms

A

eukaryotic cells

it is NOT cidal to bacteria

30
Q

What does the freezer do to eukaryotic cells?

A

frozen water forms crystals which can puncture cell walls

31
Q

What does the freezer do to bacteria?

A

it removes the water necessary for enzymatic reactions

the bacterial population does not grow (becomes static)

32
Q

What does the refrigerator do to bacteria?

A

slows the rate of enzymatic reaction but does NOT stop it

Bacteria will continue to grow slowly

33
Q

Name 2 mediums which can be used to control microorganism populations via osmotic pressure

A

brine and sugar solutions

34
Q

What happen to bacteria in a hypertonic environment?

A

they undergo plasmolysis

35
Q

What grows in brine and is it a problem?

A

only halophiles will grow but they are non pathogenic

36
Q

What grows in high sugar solutions and is it a problem?

A

saccharophilic organisms such as mold will grow in up to 70% sugar solution but they are non pathogenic

37
Q

What is a high sugar solution used for?

A

preservation of fruit (would make jams and jellies)

38
Q

What is the mode of action of sunlight as a form of microorganism control?

A

photo oxidation (of proteins)

39
Q

How long can mycobacterium TB last with dessication? with dessication AND sunlight?

A

8 month in dessication

a few days in the sun

40
Q

Name different types of radiation

A 
UV
Infrared
microwaves
gamma rays
cathode rays
x rays
41
Q

what is the mode of action of radiation?

A

destroys DNA

42
Q

Is radiation efffective against prions? why or why not?

A

no because prions only have RNA

43
Q

Is UV penetrative?

A

no

this is why sunblock is effective

44
Q

What can UV light do to seratia narcescens?

A

it can be mutated to only be white and never change back to red using laminar flow hoods

45
Q

Does UV light sterilize or disinfect?

A

disinfect

46
Q

Can UV light be used for water purification?

A

yes

BUT the water has to be very clean to begin with

47
Q

Does UV light work on spores?

A

yes

48
Q

What is the mode of action of UV light?

A

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
Q

Are infrared light and microwaves sterilizing or disinfecting?

A

disinfecting

50
Q

What can infrared light and microwaves be used on to control microorganisms?

A

can be used for the disinfection of soft contact lenses and urinary catheters

51
Q

What is the mode of action of infrared light and microwaves?

A

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
Q

Are gamma rays penetrating?

A

yes, very

except for lead

53
Q

where do gamma rays come from?

A

radioactive isotopes such as cobalt 60

54
Q

what are gamma rays used for? why?

A

sterilizing bacon and produce

to gain a longer shelf life

55
Q

do gamma rays deposit radioactive materials in meat?

A

no

56
Q

What are cathode rays? What are they used for?

A

electron beams of high intensity

sterilization of sutures

57
Q

Do cathode rays sterilize or disinfect?

A

sterilization of sutures

58
Q

Are X-rays penetrating?

A

yes of course

59
Q

Are X-rays dangerous?

A

they are too dangerous for routine use

60
Q

What forms of radiation are ionizing?

A

gamma rays
cathode rays
x-rays

61
Q

What is the mode of action of ionizing radiation?

A

uses ionizing energy to create hyperactive ions

ions strike DNA causing mutation

62
Q

Can you use ionizing radiation for sterilization or disinfection?

A

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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