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Micro : Unit 1 > Chapter 8: Control of Microorganisms in the Environment > Flashcards

Chapter 8: Control of Microorganisms in the Environment Flashcards

1
Q

Microbes are controlled by
targeting their nutrition,
growth, and development

A

• This can be done by starving,
poisoning, or inhibiting
growth or replication

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2
Q

Biocide

A

• Term used rather than antimicrobial –can be chemical,
physical, mechanical, or biological

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3
Q

Sterilization

A

all living cells, spores, and acellular entities
are destroyed or removed

• When something is sterilized it is completely free of all
viable microorganisms, spores, and infectious agents

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4
Q

Disinfection

A

killing, inhibiting, or removing
microorganisms that might → cause disease
• Reduces the population of microbes and destroys
potential pathogens

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5
Q

Disinfectants

A

carry out disinfection, used on →
inanimate objects
• Does not remove → endospores

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6
Q

Sanitization

A

partially disinfect

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7
Q

Antisepsis

A

destruction or inhibition of microorganisms
in → living tissue

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8
Q

Antiseptics

A

chemicals applied to tissue to prevent
infection by preventing pathogen growth or killing
the pathogen
• Not as toxic as disinfectants

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9
Q

Types of microbial substances:

A

• -cide suffix indicates a cidal agent that kills pathogens
(not endospores)
• Bactericide, fungicide, or viricide

• -static suffix indicates agents that do not kill but
prevent or inhibit growth
• Bacteriostatic and fungistatic

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10
Q

Microbes do not instantly die after being exposed to a
lethal agent

A

Population is reduced exponentially at constant
intervals

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11
Q

Decimal reduction time (D value)

A

time required to kill 90% of microorganisms
or endospores under certain conditions

• After a population has a major
reduction the killing can slow due to
resistant microorganisms surviving

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12
Q

Lethal agents are determined to be effective
when microbes are dead, but that can be a
challenge to determine why?

A

• Viable but nonculturable (VBNC) – bacteria
exposed to certain conditions remain alive,
but are unable to reproduce, temporarily

• Bacteria regain the ability to reproduce and
cause infection after a → recovery period

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13
Q

Viable but nonculturable (VBNC)

A

bacteria exposed to certain conditions remain alive,
but are unable to reproduce, temporarily

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14
Q

Bacteria regain the ability to reproduce and
cause infection after a

A

recovery period

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15
Q

Filtration can be used to reduce microbial populations in
→

A

heat-sensitive solutions

• Can be used to sterilize liquids and gases (air) by acting
as a barrier but does not kill microbes

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16
Q

Membrane filters

A

porous membranes filter microbes (1µm can trap endospores)
• Remove microbes by → screening them out
• Use to sterilize pharmaceuticals,
ophthalmic solutions (eye drops),
culture media, oils, antibiotics, and other
heat-sensitive solutions

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17
Q

Microorganisms can also be filtered from the → air

A

• N-95 disposable masks used in hospitals

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18
Q

High-efficiency particulate air (HEPA) filters

A

found in →biosafety cabinets
• Air moves freely but microorganisms are → resisted

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19
Q

Laminar flow safety cabinets or hoods…

A

force air through HEPA filters and sends out filtered
air across the opening of the cabinet

• The air flow protects workers from the
microorganisms being handled in the
cabinet and prevents the room from being
contaminated

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20
Q

____ heat can destroy cells and
viruses

A

Moist

Degrades proteins, nucleic acids,
and the plasma membrane of
microbes

• 10 min boiling kills vegetative 
cells but not endospores (can 
survive for hours)
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21
Q

Autoclave

A

device that uses saturated steam pressure,
121°C and 15 psi
• Hot enough to destroy → endospores

22
Q

Pasteurization

A

used on → heat-sensitive substances
• Controlled heating, briefly below boiling

• Used for milk, beer, wine, and other beverages
• Does not sterilize but kills present microbes and →
slows spoilage

23
Q

Dry heat sterilization is performed in
laboratory settings

A

Incinerate microorganisms on
inoculating loops

24
Q

Why does dry heat kill microbes?

A

Microbes die as a result of oxidation
and denaturation of cell components
and proteins
• Less effective than moist heat but
does not corrode glassware or
metal instruments
• Can destroy plastics and rubber

25
Q

Ultraviolet (UV) radiation

A

260nm is lethal to microorganisms
• Forms Thymine-thymine dimers in DNA

• UV lamps are placed on lab ceilings
or biological safety cabinets to
sterilize the air and → exposed
surfaces

26
Q

Ionizing radiation

A

sterilizes by penetrating → deep into objects
• Forms free radicals that destroy or weaken nearby
matter
• Destroys all microbial cells and endospores, but not →
viruses

27
Q

Cobalt 60 gamma radiation with high-voltage electricity is used for cold sterilization of?

A

antibiotics, hormones, sutures, and plastic supplies like syringes

Currently being used to sterilize→ meat
and other foods

• Approved by the FDA (Food and Drug
Administration) and WHO (World
Health Organization)

28
Q

Chemical disinfectants

A

Chemical disinfectants need to be effective against
many infectious agents at low concentrations and when
exposed to → organic matter

• It must be toxic to infectious agents and nontoxic to
people or corrosive
• Low effectiveness

29
Q

Chemical antiseptics

A

Chemical antiseptics are less toxic than disinfectants and
are less effective at killing microbes
• Reduce the number of pathogens to → prevent
infection
• Ex. Hand sanitizers and dilute iodine

30
Q

Overuse of chemical disinfectant and antiseptic can be hazardous

A

• There has been antimicrobial resistance seen in →
triclosan
• Found in mouthwash, deodorant, soaps, cutting
boards, and baby toys

31
Q

Phenolics

A

were the first widely used antiseptic and
disinfectants

• Used by Joseph Lister (1867) to reduce infection risks →
during surgery
• Used today as disinfectants in laboratories and hospitals
• Lysol

Phenols act by denaturing proteins and disrupting cell
membranes of microbes

32
Q

Alcohols

A

are the most widely used disinfectants,
antiseptics, and sanitizers
• Can kill bacteria, fungi, and some enveloped viruses but
→ not endospores
• Ethanol and isopropanol are most commonly used at →
60-80%
• They dissolve membrane lipids

33
Q

Iodine

A

is used as skin antiseptic and oxidizes cell
components and iodinates cell proteins to kill
• Can kill → some endospores
• Drawbacks: Damages skin, leaves a stain, and causes →
allergies

34
Q

Betadine used for _____

A

wound care

35
Q

Chlorine

A

used to disinfect water supplies and → swimming
pools
• Chlorine, sodium hypochlorite (bleach)
• Oxidizes materials in the cell and destroys vegetative
bacterial and fungi
• Almost all microorganisms will be dead 30 minutes
after exposures

36
Q

what heavy metals have been used as germicides?

A

Mercury, silver, arsenic, zinc and copper

• Less toxic germicides are used today

37
Q

Some hospitals use 1% silver nitrate on → newborn’s eyes

A
38
Q

Quaternary ammonium compounds

A

are detergents that
are used for decontamination and have broad spectrum
antimicrobial activity

39
Q

Detergents

A

– organic cleaning agents that are →
amphipathic
• Cationic detergents disrupt microbial membranes
and denature proteins

40
Q

EPA (Environmental Protection Agency) regulates →

A

disinfectants

41
Q

FDA (Food and Drug Administration) regulates agents
used on →

A

humans and animals
• Both have established guidelines for agent → use and
effectiveness
• Six factors

42
Q

Population size

A

larger populations of microbes require
longer time to die than smaller ones

43
Q

Population composition

A

the nature of the organism
impacts the effectiveness of the agent
• Ex. Endospores more resistant than vegetative cells
• Younger cells are easier to destroy than mature ones

44
Q

Concentration or intensity of an antimicrobial agent

A

higher concentrations can sometimes destroy the
organisms → quicker

45
Q

Contact time

A

the longer the exposure the more
microorganisms will be killed

46
Q

Temperature

A

higher temperatures enhance chemical
activity

47
Q

Local environment

A

can offer protection or aid in
destruction
• Heat kills better and faster with an → acidic pH
• Organism matter like biofilms can → protect

48
Q

Emerging science involving the exploitation of natural
control processes

A

Predation of microorganisms, viral-mediated lysis, and
toxin-mediated killing

49
Q

Bdellovibrio is a Gram-negative → predator

A

• Can destroy human
intestinal pathogens like
Salmonella, Shingella, and
E. coli
• Spraying poultry farms
may reduce potential
contamination

50
Q

In the early 1900s is was discovered that isolating
bacteriophages from patients with dysentery could be
used to help → fight the disease

A

• FDA recently approved the use of bacteriophage spray
to eradicate Listeria, Salmonella, and E. coli in food

Micro : Unit 1 (8 decks)

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