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Bio 232 > Week 7 > Flashcards

Week 7 Flashcards

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Biology 101 flashcards
1
Q

What chemical/physical agents are used to control growth of MO’s?

A

Heat
Radiation
Toxic chemicals

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2
Q

Microbial growth helps

A

curb the transmission of infectious microbes

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3
Q

Examples of microbial growth control practical applications

A
  • routinely wash fresh fruits and vegetables to remove attached microorganisms
  • inhibit microbial growth on body surfaces by washing.
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4
Q

Sterilization

A

killing or removal of all microorganisms (including viruses)
* In many circumstances, sterility is not required.

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5
Q

Decontamination

A

the treatment of an object or surface to make it safe
to handle

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6
Q

Disinfection

A

a process that directly targets pathogens although it
may not eliminate all microorganisms.

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7
Q

Disinfection Requires

A

agents called disinfectants
that actually kill microorganisms or severely
inhibit their growth.

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8
Q

Where is microbial growth control used extensively?

A

Industry
Medicine
Home

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9
Q

What are 3 classes of physical controls?

A
  1. Heat: is the most widely
  2. Radiation
  3. Filtration
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10
Q

How is effectiveness of heat as a sterilant quantified?

A

By decimal reduction time (D)

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11
Q

What is Decimal reduction time?

A

The time required at a given temperature for a 10-fold reduction in
the viability of a microbial population.

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12
Q

What is the relationship between D and temp?

A

exponential

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13
Q

What are the types of heat?

A
  • Moist heat has better penetrating power
  • Dry heat.
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14
Q

Temperature

A

heat killing proceeds more rapidly as the
temperature rises.

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15
Q

What is thermal decimal time?

A
  • Another way to characterize the heat sensitivity of an organism
  • The time it takes to kill all cells at a given temperature.
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16
Q

How to determine thermal decimal time?

A

Samples of a cell suspension are heated for different times, mixed with
culture medium, and incubated.
* Is independent of the original cell number
* A longer time is required to kill all cells in a large population than in a
small one.

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17
Q

What factors influence the effectiveness of heat?

A
  1. The presence of endospore-forming bacteria in a heat-treated sample can influence both the decimal reduction and thermal death times.
  2. The medium in which heating takes place
    * This is especially relevant in food canning procedures.
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18
Q

an endospore is?

A
  • very dehydrated
  • contains calcium dipicolinate
  • contains small acid-soluble spore proteins (SASPs) that help confer heat stability on the structure.
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19
Q

pH

A

Microbial death is more rapid at acidic pH, and acidic foods such as tomatoes, fruits, and pickles are easier to sterilize than neutral-pH foods such as corn and beans.

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20
Q

High concentrations of sugar, proteins, and fats do what?

A

decrease heat penetration and usually increase the resistance of organisms to heat

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21
Q

High salt concentrations do what?

A

may either increase or decrease heat resistance, depending on the organism.

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22
Q

What is an autoclave?

A

a sealed heating device that uses steam under pressure
to kill microorganisms

23
Q

What temp kills endospores?

A

endospores requires heating at temperatures
above the boiling point of water at 1 atm.

24
Q

who discovered pasteurization?

A

Louis pasteur

25
Q

How does pasteurization work?

A

At the temperatures and times standardized for the
pasteurization of food products, all known pathogenic
bacteria are killed.

26
Q

What is flash pasteurization?

A

To pasteurize milk, the liquid is passed through a tubular heat
exchanger. Careful control of flow rate and the size and temperature of
the heat source raises the temperature of the milk to 71°c for 15 sec
(or even higher temperatures for shorter time periods after which it is
rapidly cooled.

27
Q

what does pasteurization do?

A

uses heat to significantly reduce rather than
totally eliminate the microorganisms found in liquids, such
as milk.

28
Q

Physical microbial killing agents

A
  • Heat
  • Radiation
  • ultraviolet (UV) light, X-rays, and gamma rays
  • Filtration
29
Q

What does radiation need to be between to kill exposed organisms?

A

220 and 300 nm

30
Q

What is UV radiation useful for?

A

disinfecting surfaces and air

31
Q

Where do we use UV radiation in day to day life?

A

▪ to decontaminate and disinfect the work surface of laboratory laminar
flow hoods equipped with a “germicidal” UV light
▪ air circulating in the hospital
▪ food preparation rooms

32
Q

What is poor with UV radiation

A

poor penetrating power, limiting its use to the
disinfection of exposed surfaces or air

33
Q

What is ionizing radiation

A

is electromagnetic radiation of sufficient energy
to produce ions and other reactive molecular species from
molecules with which the radiation particles collide.

34
Q

The unit of ionizing radiation

A

Roentgen

35
Q

The standard for sterilization

A

the absorbed radiation dose,
measured in rads (100 erg/g) or grays (100 Gy=100 rad)

36
Q

X-rays or gamma rays

A

have sufficient energy and penetrating power
to kill microorganisms in bulk items such as food products and
medical supplies.

37
Q

Radiation is used to sterilize these pieces in lab/life

A
  • surgical supplies
  • plastic labware
  • Drugs
  • even tissue grafts
  • certain foods and food products such
  • fresh poultry
  • meat products
  • spices
38
Q

When is filtration used?

A

Heat-sensitive liquids that are not sterilized by radiation are typically
sterilized by filtration.

39
Q

what is the average filter pore size

A

0.2 μm average size is a
minimum requirement

40
Q

What are the several types of filters are in routine use in microbiology

A

depth filters
*membrane filters
*nucleopore filters.

41
Q

What are depth filters?

A

a fibrous sheet made from an array of overlapping paper
or glass fibers that traps particles in the network of fibers

42
Q

What are membrane filters

A
  • The most common filters used for liquid sterilization in the
    microbiology laboratory
  • Composed of high-tensile-strength polymers
    manufactured in such a way as to contain a large number
    of tiny pores.
43
Q

What are nucleopore filters

A

A type of membrane filter
* Made from a thin polycarbonate film that is treated with
radiation and then etched with a chemical, yielding very
uniform-sized holes.

44
Q

What are nucleopores commonly used for?

A

to isolate
specimens for scanning electron microscopy.

45
Q

cidal agents

A

Agents that actually kill are called -cidal agents, with a prefix indicating the type
of microorganism killed
* Bactericidal agent
* Fungicidal agent
* viricidal agent

46
Q

static agents

A

Agents that inhibit growth are called -static agents,
* bacteriostatic agent
* Fungistatic compounds
* viristatic compounds

47
Q

what is an AMA

A

natural or synthetic chemical that kills or inhibits the
growth of microorganisms.

48
Q

Antibacterial agents are classified as

A

-static, -cidal, or -lytic

49
Q

bacteriostatic agents

A

typically inhibitors of some important biochemical process
* bind relatively weakly
* if the agent is removed, the cells can resume growing.
* Some antibiotics, such as the sulfonamides, work in this
way.
* The clinical value of bacteriostatic antibiotics is their ability
to keep a pathogenic bacterium from multiplying until the
immune system can rid the body of the pathogen.

50
Q

Bactericidal agents

A

bind tightly to their cellular targets and by definition kill the
cell.
* the dead cells are not lysed, and total cell numbers,
reflected in the turbidity of the culture, remain constant.
* for example formaldehyde

51
Q

Bacteriolytic agents

A

kill cells by lysing them
* affects both viable and total cell numbers
* Example:
* detergent that ruptures the cytoplasmic membrane
* the antibiotic penicillin, which inhibits bacterial cell wall
synthesis, resulting in cell lysis.

52
Q

What is the minimum inhibitory concentration (MIC)

A

determining the smallest amount of the agent needed to
inhibit the growth of a test organism

53
Q

What is one way to determine MIC of a given agent

A

inoculate a series of tubes of liquid growth medium
containing a test organism and dilutions of the agent.

Bio 232 (9 decks)

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