EXAM 2- Chapter 7- part 4 Flashcards
What is sterilization?
Destruction or removal of all viable organisms
It is the most comprehensive level of microbial control.
What are disinfectants?
Substances that kill, inhibit, or remove disease-causing organisms
used on inanimate objects
Used primarily on inanimate objects.
What is sanitization?
Reduction of microbial population to meet some standard
Aimed at lowering the microbial load.
What is antisepsis?
Destruction or inhibition of microorganisms on living tissue
Antiseptics are used for this purpose.
What are antiseptics?
Substances used on living tissue to prevent sepsis
Typically used at lower concentrations than disinfectants.
What is chemotherapy in the context of microbiology?
Use of chemicals to kill or inhibit growth of microorganisms within host tissue
Aimed at treating infections.
Define antimicrobial agents.
Agents that kill microorganisms or inhibit their growth
Includes both cidal and static agents.
What are cidal agents?
Agents that kill microorganisms directly
Named after the specific organism they target.
What are static agents?
Agents that inhibit the growth of microorganisms
Allowing the immune system time to respond.
What influences the efficacy of antimicrobial agents?
population size and composition
concentration/intesity of agent
contact time
temperature
local environment
Each factor affects how effective an agent will be.
How does population size affect efficacy of antimicrobial agents?
Larger populations take longer to kill than smaller populations
Death occurs exponentially.
How does population composition affect efficacy of antimicrobial agents?
Microorganisms differ in their sensitivity to antimicrobial agents
Factors include age of cells and presence of spores.
Fill in the blank: Higher concentrations or intensities of microbial agents usually kill more rapidly, but _______ is an exception.
ethanol
70% ethanol is most effective due to dehydration of cells.
What is contact time?
Duration of exposure to an antimicrobial agent
Longer exposure typically results in more organisms killed.
How does temperature affect efficacy of antimicrobial agents?
Higher temperatures usually increase the rate of killing
Heat increases molecular motion.
What is decimal reduction time (D-value)?
Time to kill 90% of microorganisms and spores in a sample under specific conditions
A lower D-value indicates a more effective agent.
Normal filtration
will remove all bacteria
to remove viruses requires ultrafiltration methods
Normal filtration removes bacteria; ultrafiltration is needed for viruses.
What is the role of N-95 masks?
Removes 95% of particles that are 0.3 micrometers or larger
Effective for protecting against aerosolized pathogens.
What is steam sterilization?
Effective against all types of microorganisms including spores
must be carried out above 100C which requires saturated steam under pressure
Requires saturated steam under pressure, typically done in an autoclave.
What is the purpose of indicator tape in autoclaving?
To verify that the correct temperature and pressure have been achieved
Changes color when conditions are met.
What cannot be sterilized in an autoclave?
Plastics, some metals, anything that repels water, and items that need to maintain structural integrity
Examples include oil/wax and certain papers.
What is pasteurization?
Disinfectant
Controlled heating at temperatures well below boiling to kill pathogens
Used for beverages like milk and beer.
How is dry heat sterilization different from moist heat sterilization?
less effective- Requires higher temperatures and longer exposure times
Effective for items that cannot be exposed to moisture.
What is UV radiation?
Disinfection
using electromagnetic radiation to control microbes
UV radiation does not kill spores.
What wavelengths of UV radiation can damage DNA?
260-280 nm
alpha and beta rays
These wavelengths form thymine dimers.
What is one example of using UV radiation for disinfection?
Disinfecting air in lab hoods
using direct sunlight to disinfect water
Direct sunlight can also disinfect water.
What type of radiation is referred to as ‘cold sterilization’?
Ionizing radiation
Gamma radiation penetrates deep into objects.
What does ionizing radiation destroy?
Bacterial endospores
Not always effective against viruses.
When to use ionizing radiation
- Sterilization of antibiotics
- Sterilization of hormones
- Sterilization of sutures
- Sterilization of plastic disposable supplies
- Sterilization of food
What is the disk-diffusion method used for?
Evaluating a disinfectant
if zone of inhibition is present it is effective
A zone of inhibition indicates effectiveness.
How do phenolics work?
Antiseptic and disinfectant
denature proteins and disrupt cell membranes- aromatic rings can wiggle between membranes
They denature proteins and disrupt cell membranes.
Where are phenolics commonly used?
With organic matter- active in presence of organic matter
Hospital and laboratory disinfectants
Example: tuberculocidal.
What are limitations of phenolics
Disagreeable odor
can cause skin irritation
Can cause skin irritation.
How do aldehydes work
Sporicidal and chemical sterilant
highly reactive- react with DNA and proteins- randomly adds alpha groups
They react with DNA and proteins.
Name two commonly used aldehyde agents.
- Formaldehyde
- Glutaraldehyde
What do alcohols do?
Disinfectant and antiseptics; not sporocidal
denature proteins and possibly disolve membrane lipids
inactivate envelope viruses
They denature proteins and dissolve membrane lipids.
What are the two most common alcohol agents?
- Ethanol
- Isopropanol
What is the concentration range for effective alcohol use?
60-80%
How does iodine work?
Skin antiseptic; can also be used as sterilant
oxidizes cell constituents and iodinates proteins
at high conc. it can kill spores
Iodophore oxidizes cell constituents.
What is a limitation of iodine as a disinfectant?
Can cause skin damage
stains
allergies can be a problem
Stains and allergies may also be a problem.
What is chlorine used for?
Disinfectant as liquid, sterilant as gas
oxidizes cell constituents and destroys vegetative bacteria/fungi
Chlorine gas kills spores
Destroys vegetative bacteria and fungi.
What is a limitation of chlorine?
Can react with organic matter to form carcinogenic compounds.
What do heavy metals do?
Combine with and inactivate proteins
may also precipitate proteins- pull out of solution
They may also precipitate proteins.
Name some examples of heavy metal ions.
- Mercury
- Silver
- Arsenic
- Zinc
- Copper
How do quaternary ammonium compounds work?
Disinfectant/antiseptic
amphipathic organic cleasing agents that act as wetting agents and emulsifiers
disrupt membranes and denatures proteins
They are amphipathic organic cleansing agents.
What is a limitation of quaternary ammonium compounds?
Not effective against Mycobacterium tuberculosis or endospores
can be inactivated by hard water and soap
What is ethylene oxide used for?
Sterilization of heat-sensitive materials
It is microbiocidal and sporocidal.
What type of equipment is used for ethylene oxide sterilization?
Equipment resembling an autoclave.
What is a characteristic of ethylene oxide?
Very strong alkylating agent.
Name two other sterilizing gases.
- Beta propiolactone
- Vaporized hydrogen peroxide
T/F Some agents can be used as both disinfetants and antiseptics
TRUE
but are used at different concentrations
Antiseptics are lower conc.
Why do you want to inhibit growth with static agents?
so immune system has time to amount a response
keeps pathogens from getting out of hand
Four types of composition to consider for antimicrobial agent
- old VS young cell- older are harder to kill-deploy defenses
- mix of microorganism- spores harder to kill
- mycolic acid content- high mycolic acid mircroorgs. harder to kill
- Gram- gram-negative are harder to kill
How does concentration of agent affect efficacy of antimicrobial agents?
usually higher concentrations kill more rapidly
EXCEPTION- EtOH
How does Contact time affect efficacy of antimicrobial agents?
longer exposure= more organisms killed
gives agent more time to make its way into the population then into cells
What are environmental factors that impact effectiveness?
pH
Viscosity- takes agents longer to move through environment
Conc. of Organic Matter- some agents interact with organic mater before going to cells
Pattern of microbial death
microorganisms are not killed instantly
population death usually occurs exponentially
T/F want a lower D-value
TRUE
kills faster and is more effective
What are the three physical control methods?
filtration
heat
radiation
Limitations of normal filtration
large particles clog filters
ultrafiltration requires high pressure
viscous liquids dont filter well
Membrane filter sterilization
Removes microorganisms from heat sensitive liquids
When to use membrane filter sterilization?
when we cannot use heat to sterilize
EX. antibiotics
High Efficiency particulate air (HEPA) filters
Disinfecting
used in laminar flow biological safety cabinets
removes 99.97& of particles 0.3 um or larger
How does HEPA filters work
physical and electrostatic interactions
When to use HEPA filters
with pathogens that can be aerosolized
Heat
proteins and nucleic acids are disrupted
Heat Example
boiling- disinfectant
does not kill spores
Freezing
can stop biochemical reactions in microbes in the presence of a buffer
What happens when a buffer is not used for freezing?
ice crystals form and can damage cells
Autoclave- quality control
- indicator tape
- Ampules of geobacillus stearothermophilis
Autoclave- ampules
do this if using spore forming bacteria
Put ampules on plate and if nothing grows autoclave is working
Why do we not want to overload autoclave
The steam cannot move over everything to sanitize if its over crowded
Tyndallization
intermittent sterilization- 30-60 min of steam repeated 3 times with 24 hr incubation between
How does tyndallization kill spores
Does not kill them in spore form
forces spores to germinate into metabolic form
then second blast either kills or further germinates
Problems with tyndallization
cant ever be sure all the spores have germinated and been killed
How pasteurization works
does not sterilize but kills pathogens present and slows spoilage time by reducing microbial load
What is pasteruization used for?
beverages
milk
beer
How does dry heat sterilization work?
oxidizes cell constituents and denatures proteins
When to use dry heat sterilization?
metals that rust
things that repel water- oil/wax
Dry heat incinerator
bench top incinerators used to sterilize inoculating loops
How does UV radiation disinfect?
damages DNA and forms thymine dimers
ionizing radiation
sterilizing radiation/gamma radiation penetrates deep into objects
3types of chemical control methods
disinfection
antisepsis
sterilization
Examples of Phenolics
tuberculocidal- effective in presence of organic material and long lating
triclosan (hand sanitizer)- bacteria can become resistant
Limitations of heavy metals
Effective but TOXIC
Why would we want to use Quaternary ammonia compounds?
safe and easy to use
rarely causes irritation
What is refered to as cold sterilization
sterilizing gas
Ethylene oxide
