Chapter 13 Flashcards
(52 cards)
1
Q
clean is a relative term
A
- microbial load can be reduced by washing, vacuuming, and dishwashing but, is this clean enough
- depends on the intended use of an object/surface
2
Q
why clean and not sterilize everything
A
- sterilization often requires time, is labor intensive, and may degrade the quality of the item being treated, or even have toxic effects on users
3
Q
Biosafety levels
A
ranked by the severity of disease and ease of transmission
4
Q
BSL-1
A
- generally does not cause infection in healthy human adults
- noninfectious bacteria and viruses known to infect animals other than humans
- few precautions necessary
5
Q
BSL-2
A
- pose moderate risk to lab workers and the community
- typically “indigenous”= commonly found in that geographical area
- need restricted access, PPE, self-closing doors, eyewash, autoclave
6
Q
BSL-3
A
- can cause lethal infection by inhalation
- can be indeigenous or “exotic”
- restricted access
- medical surveillance, vaccination, respirator, biological safety cabinets at all times
- hands-free sink, eyewash, self-closing and locking doors
- directional air flow
7
Q
BSL-4
A
- most dangerous and often fatal
- exotic pathogens, easily transmitted by inhalation, cause infection with no treatment/vaccination
- must change clothes when enter lab, shower before leaving, decontaminate all material when exiting
- full body protective suit, designated air supply
- lab needs to be in seperate building ot have its own air supply and exhaust
8
Q
sterilization
A
- process by which all living cells, spores, and viruses are destroyed on an object
9
Q
disinfection
A
- the killing/removal of disease-producing organisms from inanimate surfaces
- does not necessarily result in sterilization
10
Q
antisepsis
A
- similar to disinfection but applies to removing pathogens from the surface of living tissues, such as skin
11
Q
sanitation
A
- consists of reducing the microbial population to safe levels and usually involves cleaning an object as well as disinfection
12
Q
sepsis
A
bacteria in blood
13
Q
degerming
A
killing microbes from limited area
14
Q
cidal agents
A
- kill microbes
- bactericidal, algicidal, fungicidal, virucidal depending on what type of microbe is killed
15
Q
static agents
A
- inhibit/control growth
- bacteriostatic, algistatic, fungistatic, virustatic, depending on what type of microbe is inhibited
16
Q
selection of a disinfectant
A
- must be fast acting in the presence of organic materials
- must bee effective against all microorganisms without destroying tissue or acting as a toxin if ingested
- easily penetrate the material to be disinfected without discoloration or damage
- easy to prepare and stable in the environment where it is to be used
- inexpensive and easy to use
- not have an unpleasant odor
no perfect disinfectant that meets all criteria
17
Q
microbial death curve
A
- the degree of microbial control can be evaluated using a microbial death curve to describe the progress and effectiveness of a particular protocol
- when exposed to a particular microbial control protocol, a fixed percentage of the microbes within the population will die. Because the rate of killing remains constant even when the population size varies, the percentage killed is more useful information than the absolute number of microbes killed
- death curves are often plotted as semilog plots just like microbial growth curves because the reduction in microorganisms is typically logarithmic
- the amount of time it takes for a specific protocol to produce a one order of magnitude decrease in the number of organisms or the death of 90% of the population is called the decimal reduction time (DRT/D-value)
18
Q
DRT
A
- D-value
- decimal reduction time
- the amount of time it takes for a specific protocol to produce a one order of magnitude decrease in the number of organisms, or the death of 90% of the population
19
Q
factors that influence the speed at which lethal damage accumulates
A
- the initial population size (larger population= longer to decrease)
- population composition (are spores involved?)
- agent concentration or dose for radiation
- duration of exposure
- presence of organic material (blood, feces) that can inhibit disinfectant action; organic load
20
Q
can microbes be controlled without chemicals
A
- physical agents are often used to kill microbes or control their growth
- commonly used physical control measures include: extreme temp, pressure, filtration, irradiation
21
Q
high temperature and pressure
A
- moist heat is very effective at killing microbes
- dry heat is less effective but sometimes requires
22
Q
moist heat
A
- more effective at killing microorganisms than dry heat because it denatures and coagulates proteins, which are essential for microbial function, while dry heat primarily oxidizes proteins, requiring higher temperatures and loger exposure times
23
Q
how to kill spores and thermophiles
A
- combination of heat nad pressure is usually requires
24
Q
autoclave condition
A
121 degrees C at 15 psi (pounds per square inch) for 20 minutes
25
12D methos
- amount of time requires to kill 10^12 spores or reduce the population by 12 logs
- finding 10^12 spores in food is highly unlikely, a 12D treatment will produce food that is safe.
- this measurement is extremely important to the canning inducstry in order to ensure that canned goods do not contain Clostridium botulinum spores
26
heat killing
- preferred sterilizing agent as it does not damage the materials
27
thermal death point
- lowest temperature that kills all the bacteria in a 24 hour old culture/10 minutes
28
thermal death time
- teim required to kill all the bacteria in a culture at a specified temperature
29
decimal reduction time
- length of time required to kill 90% of the organisms in a population at a specific temperature
30
pasteurization
- doesn't sterilize
- kills pathogens without affecting the texture, color, or taste of the product
- heating a particular food to a moderately high temp long enough to kill Coxiella burnetii, the causative agent of Q fever and most heat resistant spore-forming pathogen known
31
low temperature long time
- pasteurization
- involves bringing the temp to 63 degrees C for 30 minutes
32
high temperature short time
- pasteurization
- flash pasteurization
- brings temperature to 72 degrees C for only 15 seconds
33
ultra high temperature
- pasteurization
- brings temperature to 138 degrees C for 2 seconds
- can produce sterilizes products with unrefrigerated shelf lives up to 6 months
34
cold
- low temps have 2 basic purposes in microbiology: to temper growth and to preserve strains
- bacteria grow more slowly in cold temperatures, but they also die more slowly
35
refrigeration, freezing
- excellent to preserve food and other materials-- retards microbial growth
- does not effectively kill microorganisms
- microorganisms can be stores this way
- long term storage of bacteria usually requires placing solutions in glycerol at very low temp--> depp freezing suspends growth altogether and keeps cells from dying
36
freeze drying
- lyophilization
- cultures are quickly frozen at very low temperatures and placed under a vacuum, which causes the water to sublimate, removing all water from the cells
- many microorganisms are sensitive to drying-- but many are not
- freeze-drying is used for storing many microorganisms
37
filtration
- many drugs/chemicals are sensitive to heat or other chemical sterilization methods
- these solutions can be sterilized by passing them through sterile filters with tiny pores that effectively "sift" the microbes out of the fluid
- filtration through micropore filters of 0.2 micrometers can remove microbial cells, but not viruses
- to remove viruses, pore size of 20 nm are necessary
- air can be sterilized through filtration
38
laminar flow biological safety cabinets
- elaborate and effective ventilated workbenches in which air is forced through filters to remove microbes
- example of HEPA filter
39
HEPA
- removes microbes >0.3 micrometers
- small enough to capture bacterial cells, endospores, and many viruses
40
membrane filtrations
removes microbes >0.22 micrometers
- removes microbes from liquid samples
- useful for heat sensitive solutions, culture media
41
sonication
- high frequence ultrasound waves to disrupt cell structures
- leads to cavitation, the formation of bubbles inside the cell, which can disrupt cell structures and eventually cause the cell to lyse/collapse
- disruption is achieved due to the rapid changes in pressure within the intracellular liquid
- useful in laboratory for efficiently lysing cells to release their contents for further research
- used for cleaning surgical instruments, lenses, and a variety of other objects such as coins, tools, and musical instruments
42
irradiation
- method in which objects are bombarded with high-energy electromagnetic radiation
- foods do not become radioactive when irradiated, and any reactive molecules produced when high-energy particles are absorbed by food dissipate almost immediately
- UV light is useful only for surface sterilization due to its poor penetrating ability
- gamma rays, electron beams, X rays
43
efficacy of a given chemical agent depends on...
- presence of organic matter (chemicals will bind to organic material, lowering its effectiveness against microbes)
- the kinds of organism present(ideally should be effective against a broad range of pathogens
- corrosiveness(should not corrode the surface--living or nonliving)
- stability, odor, and surface tension(should be stable upon storage, neutral or pleasant odor, low surface tension
44
ethanol, iodine, chlorine
- highly reactive compounds that damage proteins, lipids, and DNA
45
surfactants
- such as detergents
- help in the mechanical removal of microbes from surfaces
46
aldehydes
- combine with and inactivate proteins and nucleic acids
47
phenolics
denature proteins and disrupt membranes
48
heavy metals
bind to proteins and inhibit enzymatic activity
49
peroxygen
- strong oxidizers
- produce free radicals that damage cellular macromolecules
50
gas sterilization
- disposable plastic ware such as petri dishes, syringes, sutures, and catheters are not amenable to heat sterilization or chemical disinfection
- these types of products are best sterilized by gamma irradiation or antimicrobial gases, such as ethylene oxide
51
key characteristics of gas sterilization
- destroys proteins by alkylation
- microbicidal/sporicidal
- rapidly penetrates packing materials, including plastic wraps
- highly explosive
52
bacterial resistance to disinfectants
- bacteria can develop resistance o chemical disinfectants used to prevent infections
- it is difficult for bacteria to develop resistance to chemical agents that have multiple targets and can easily diffuse into a cell (ex: iodine)
- disinfectants that have multiple targets at high concentrations may only have a single target at low concentrations-- a situation that can foster resistance (ex: triclosan)
