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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
Ultraviolet (UV) radiation
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
Ionizing radiation
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
Cobalt 60 gamma radiation with high-voltage electricity is used for cold sterilization of?
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
Chemical disinfectants
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
Chemical antiseptics
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
Overuse of chemical disinfectant and antiseptic can be hazardous
• There has been antimicrobial resistance seen in → triclosan • Found in mouthwash, deodorant, soaps, cutting boards, and baby toys
31
Phenolics
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
Alcohols
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
Iodine
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
Betadine used for _____
wound care
35
Chlorine
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
what heavy metals have been used as germicides?
Mercury, silver, arsenic, zinc and copper • Less toxic germicides are used today
37
Some hospitals use 1% silver nitrate on → newborn’s eyes
38
Quaternary ammonium compounds
are detergents that are used for decontamination and have broad spectrum antimicrobial activity
39
Detergents
– organic cleaning agents that are → amphipathic • Cationic detergents disrupt microbial membranes and denature proteins
40
EPA (Environmental Protection Agency) regulates →
disinfectants
41
FDA (Food and Drug Administration) regulates agents used on →
humans and animals • Both have established guidelines for agent → use and effectiveness • Six factors
42
Population size
larger populations of microbes require longer time to die than smaller ones
43
Population composition
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
Concentration or intensity of an antimicrobial agent
higher concentrations can sometimes destroy the organisms → quicker
45
Contact time
the longer the exposure the more microorganisms will be killed
46
Temperature
higher temperatures enhance chemical activity
47
Local environment
can offer protection or aid in destruction • Heat kills better and faster with an → acidic pH • Organism matter like biofilms can → protect
48
Emerging science involving the exploitation of natural control processes
Predation of microorganisms, viral-mediated lysis, and toxin-mediated killing
49
Bdellovibrio is a Gram-negative → predator
• Can destroy human intestinal pathogens like Salmonella, Shingella, and E. coli • Spraying poultry farms may reduce potential contamination
50
In the early 1900s is was discovered that isolating bacteriophages from patients with dysentery could be used to help → fight the disease
• 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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