Lecutre 9 Flashcards
What are the 4 results of methods of microbial control used outside of the body?
Sterilization
disinfection
decontamination (also called sanitization)
antisepsis
Who are the targets of microbial control?
Primary targets of microbial control are microorganisms capable of causing infection or spoilage in the environment or on the human body
What are considered the most resistant microbes?
bacterial endospores
What is the goal of sterilization?
The goal of any sterilization process is the destruction of bacterial endospores
any process that kills endospores will invariably kill all less resistant microbial forms
In microbial control what is the difference between an agent and process?
agent- something that aids in microbial control
process- is how microbes are controlled
Is sterilization and disinfection an agent or process?
processes
Is bactericide an agent or process?
agent, chemical that destroys bacteria except for those at the endospore stage
Is fungicide an agent or process?
agent, chemical that can kill fungal spores
Is virucide an agent or process?
agent, chemical known to inactivate viruses, especially on living tissue
Is sporicide an agent or process?
an agent capable of destroying bacterial endospores
Is germicide/microbicide an agent or process?
agent, chemical agents that kill microorganisms
What is sepsis?
the growth of microorganisms in the blood and other tissues
What is asepsis?
Process, any practice that prevents the entry of infectious agents into sterile tissues and thus prevents infection
What are antispetics?
process, chemical agents applied directly to exposed body surfaces (skin and mucous membranes), wounds, and surgical incisions to prevent vegetative pathogens
Is bacteristatic an agent or process?
agent, chemical agents that prevent the growth of bacteria on tissues or on objects in the environment
Is fungistatic an agent or process?
agent, chemicals that inhibit fungal growth
What is microbial death?
permanent termination of an organism’s vital processes
microbes have no conspicuous vital processes, therefore death is difficult to determine
permanent loss of reproductive capability, even under optimum growth conditions has become the accepted microbiological definition of death
What are the factors the affect the death rate?
begins when a certain threshold of microbicidal agent is met
death continues in a logarithmic manner as the time or concentration is increased
active cells tend to die more quickly than less metabolically active cells
Eventually, a point is reached at which survival of any cells is highly unlikely; this point is equivalent to sterilization
What are the cellular targets of heat and radiation?
they target the widest range of microbes because they are the least selective
Are drugs selective or not?
They are very selective and only target a single cellular component
What are the cellular targets of physical and chemical agents?
cell wall
cell membrane
cellular synthetic processes
proteins
Are elevated temperatures microbicidial or microbistatic?
microbicidial
Are lower temperatures microbicidial or microbistatic?
microbistatic
Is moist heat or dry heat hotter?
dry heat
What is Thermal death time (TDT)?
shortest length of time required to kill all test microbes at a specified temperature
What is Thermal death point (TDP)?
the lowest temperature required to kill all microbes in a sample in 10 minutes
What is autoclave? pressure? temp? time?
steam under pressure (15 psi)
Can reach 121ºC
Steam driven into materials, kills microbes
Can adjust time depending on what is being autoclaved
Only for heat-resistant materials
What is intermittent sterilization?
Aka tyndallization Reservoir of boiling water Expose to steam 30-60 min Incubate 23-24 hrs (spore germination) Repeat steam treatment Do this for 3 days in a row Doesn’t get rid of highly resistant spores that may not germinate in 3 days
Does pateruization sterilize milk?
No it affects viruses and vegetative cells
What does boiling do to microbes?
30 minutes will kill most non-sporeforming pathogens; easy to contaminate when removing
What does incineration do to microbes?
Flame, electric coil
Bunsen burner 1,870ºC
Furnace up to 6,500ºC
Fast and effective, but only on very heat stable material
What does baking do to microbes?
Hot air oven
150-180ºC, 2-4 hrs
Glassware, metals, powders, oils
No liquids - evaporation
What is the benefit of cold treatment for microbes?
Principal benefit of cold treatment is to slow growth of cultures and microbes in food during processing and storage
Cold merely retards the activities of most microbes
What do the temperatures of -70 to -135 celcius do for microbes?
can preserve cultures of bacteria, viruses, and fungi for long periods
What do psychophiles have to cold temperatures?
Psychrophiles grow slowly at freezing temperatures and can secrete toxic products
what are the pathogens that are able to survive several months in the fridge?
Staphylococcus aureus
Clostridium species
Streptococcus species
Salmonella
yeasts, molds, and viruses
What is desiccation?
vegetative cells directly exposed to normal room temperature gradually become dehydrated
What is lyophilization?
combination of freezing and drying
method of preserving microorganisms in a viable state for many years
pure cultures are frozen instantaneously and exposed to a vacuum that removes water, avoiding the formation of ice crystals
What is radiation?
Energy emitted from atomic activities and dispersed at high velocity through matter or space
gamma rays
X rays
ultraviolet radiation (thymidine dimers, next slide)
is osomotic a sterlizing technique?
NEVER
What are aqueous solutions?
chemicals dissolved in pure water as the solvent
What are tinctures?
chemicals dissolved in pure alcohol or water-alcohol mixtures
How are germicides evaluated?
in terms of their effectiveness in destroying microbes in medical and dental settings
high-level germicides kill endospores and can be used as sterilants
intermediate-level germicides kill fungal, but not bacterial spores, resistant pathogens, and viruses
low-level germicides eliminate only vegetative bacteria, vegetative fungal cells, and some viruses
What is the percentage of ethyl alcohol?
70
What is the percentage of hydrogen peroxide ?
3
How and why are dyes used as antimicrobial agents?
active against gram-positive bacteria and fungi
sometimes incorporated into solutions and ointments to treat skin infections
limited application because they stain and have a narrow spectrum of activity
How and why are acids and alkalis dyes used as antimicrobial agents?
very low or very high pH can destroy or inhibit microbial cells
limited in applications due to their corrosive, caustic, and hazardous nature
ammonium hydroxide used in detergents, cleaners, and deodorizers
organic acids used in food preservation
