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MBIO 1010 > Lecture 6: Control of Microbial Growth > Flashcards

Lecture 6: Control of Microbial Growth Flashcards

1
Q

________: The killing or removal of all viable organisms within a growth medium

A

sterilization

even endospores!

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2
Q

______: Effectively limiting microbial growth

No killing taking place

A

inhibition

only acceptable when someone has a functioning immune system, basically just allows your immune system time to “catch up”!

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3
Q

_______: The treatment of an object to make it safe to handle

A

decontamination

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4
Q

______: Directly targets the removal of all pathogens

Not necessarily all microorganisms

A

disinfection

is it really true that it kills only pathogens? who knows!

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5
Q

_____ is the most widely used
method of controlling microbial growth

A

Heat sterilization

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6
Q

why do we use heat sterilization to control microbial growth?

A

High temperatures denature macromolecules, resistant cells (endospores) can still survive heat

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7
Q

Amount of time required to reduce viability tenfold is called the _______

A

decimal reduction time
(D)
Time it takes for a 10 fold reduction in bacterial numbers

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8
Q

________: is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids

A

Pasteurization
Does not kill all organisms -> not sterilization!!

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9
Q

when treating milk, how many time and temperature combinations for pasteurization can be used?

A

many! can use LTLT (low-temp/long-time) ex: 63 C for 30 mins

or HTST (high-temp/short-time) ex: 72 C for 15 secs

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10
Q

why can we use so many different combinations of time/temp for treating milk?

A

Both processes kill Coxiella burnetii, the causative agent of Q fever, which is
the most heat resistant pathogen found in milk

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11
Q

The ______ is a sealed
device that uses steam under
pressure

A

autoclave

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12
Q

why do we use liquid (steam) to sterilize using an autoclave?

A

liquid does a much better job at transferring heat! think of a dry, hot oven vs. boiling water, one transfers heat much more strongly!

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13
Q

what settings is an autoclave typically set to?

A

121oC for 15 min at 15 pounds per square inch of pressure is
typically used

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14
Q

T/F: To ensure sterility this means that the point that takes the longest to heat must stay at 121
for 15 min

A

true!

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15
Q
A
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16
Q

_______: physical method of growth control

A

radiation
Microwaves, UV, X-rays, gamma rays, and electrons can reduce
microbial growth

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17
Q

why can radiation be used to reduce microbial growth?

A

UV has sufficient energy to cause modifications and breaks in DNA, used to decontaminate surfaces by killing bugs!

18
Q

T/F: UV Cannot penetrate solid, opaque, or light-absorbing surfaces

A

true

19
Q

_____: Electromagnetic radiation that produces
ions and other reactive molecules generates electrons, hydroxyl radicals,
and hydride radicals

A

ionizing radiation

20
Q

T/F: Some microorganisms are more
resistant to radiation than others

A

true!

21
Q

T/F: amount of energy (radiation) required to reduce
viability tenfold is analogous to D value

A

true!

22
Q

what are three sources of radiation?

A

cathode ray tubes, X-rays, and radioactive nuclides

23
Q

_______ is used for sterilization in the medical field and food industry

approved by the WHO and is used in the USA for
decontaminating foods particularly susceptible to microbial contamination

A

Radiation
hamburger, chicken, spices may all be irridiated

24
Q

____ avoids the use of heat on sensitive liquids and gases

A

Filtration!

Pores of filter are too small for organisms to pass through
* Allow liquid or gas to pass through
* Ex) HEPA filters, membrane filters

25
Q

with the use of membrane filters, filtration can be accomplished by what three devices?

A

syringe
pump
vacuum

26
Q

what are the three classifications of antimicrobial agents?

A

bacteriostatic
bacteriocidal
bacteriolytic

27
Q

______: prevents cell growth as long as the antimicrobial agent is
present

A

Bacteriostatic

maintains level and prevents more growth… until drug goes away! still need to give something that will kill all unwanted bugs

28
Q

_____: kills the cells (does not lyse them)

A

Bacteriocidal

29
Q

______: kills and lyses the cells

A

Bacteriolytic

DNA is released when cells are lysed, other bugs can pick that up and change their phenotype… to our disadvantage!

30
Q

which antimicrobial agent(s) results in total and viable cell counts being the same?

A

bacteriostatic and bacteriolytic

31
Q

which antimicrobial agent(s) results in total and viable cell counts being different?

A

bacteriocidal

32
Q

________: The smallest amount of an agent needed to inhibit growth of a microorganism

A

Minimum inhibitory concentration (MIC)

33
Q

T/F: the minimum inhibitory concentration is the same in all organisms

A

false! Varies with the organism used, inoculum size, temperature, pH, etc.

34
Q

in test tube experiments, the Lowest concentration with no growth = ______

A

MIC
May still have living (non-growing) organisms
* i.e. the antibiotic may be bacteriostatic

35
Q

when broth aliquots from MIC are plated on agar plates should colonies form?

A

yes! MIC should only inhibit the growth of new bacteria, NOT kill

36
Q

if no colonies form on agar plate from broth aliquots of antibiotics, what is this called?

A

Minimal Lethal Concentration (MLC)
kills everything! colonies will not form on agar plate

37
Q

_______:
* Uses solid media
* Antimicrobial agent is added to filter paper disc
* The MIC is reached at some distance
* Forms a zone of inhibition
* Area of no growth around disc

A

Disc diffusion assay

38
Q

what two categories can antimicrobial agents be divided into?

A

Products used to control microorganisms in commercial and industrial applications

Products designed to prevent growth of human pathogens in inanimate
environments and on external body surfaces

39
Q

what are some examples of antimicrobial agents used in commercial and industrial applications?

A

chemicals in foods, air conditioning cooling towers, textile and paper
products, fuel tanks

not worried about living tissue! can be harsher

40
Q

what are some examples of antimicrobial agents used for human pathogens?

A

sterilants, disinfectants, sanitizers, antiseptics

MBIO 1010 (12 decks)

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