methods of microbial control Flashcards
process that destroys less than 100% of microbes on non-living surfaces. Unable to kill endospores which are the most difficult type of microbe to treat. Examples include applying 5% bleach soln to an operating table and boiling eating utensils after use by sick patients
Disinfection
Process that destroys 100% of microbes (even endospores) on non-living surfaces.
Sterilization
process that destroys less than 100 % of microbes on living surfaces. Examples include swabbing skin with iodide prior to surgery and washing your hands with soap.
Antisepsis
any process that removes microbes and other debris or contaminants to “safe levels.” Examples include washing plates and cups.
Decontamination
Microbicidal/microbistatic:
agents that kill microbes
Microbicidal
Microbicidal/microbistatic:
agents that temporarily inhibit the reproduction of microbes, but do not kill them.
Microbistatic
Factors that affect the rate at which microbes are killed include:
ENARA
1) exposure time to agent (the longer the material is exposed to agent, the more microbes will be killed)
2) number of microbes present on surface (the more microbial contamination, the longer it will take to disinfect it)
3) amt of organic debris or contaminants
4) resistance level of microbes (endospores vs non-endospores);
5) activity level of the agent (cidal versus static).
Category of microbial control methods:
Include heat, filtration, UV radiation and US vibration
Physical control method
Category of microbial control methods:
Include the use of sterilants, disinfectants, antiseptics and sanitizers
Chemical control method
Category of microbial control methods:
Include filtration and US vibration
Mechanical control method
Antimicrobial agents damage microbes by disrupting the:
1) cell wall;
2) cell membrane;
3) proteins;
4) NA (DNA or RNA).
T or F:Mechanical agents (filtration) physically remove microbes but do not kill them.
True
Non-ionizing/ionizing radiation:
causes breakage in microbial DNA.
Ionizing radiation
Non-ionizing/ionizing radiation:
uses ultraviolet light to form dimers between neighboring thymines in the DNA.
Non-ionizing radiation
effective physical control agent that can be delivered in both moist (steam sterilization, pasteurization) and dry (bacti-cinerators and ovens) forms.
Heat
Heat helps control microbial growth by…
Destroying or denaturing structural and regulatory proteins.
Chemical antimicrobials range from low-level disinfectants, to intermediate-level disinfectants, to high-level sterilants. Antimicrobial chemicals include:
SCHHAAPPP
1) halogens;
2) phenolics;
3) chlorhexidine;
4) alcohols;
5) peroxides;
6) soaps and detergents;
7) heavy metals;
8) aldehydes; and
9) preservatives.
Microbial control (reduction and elimination) methods can be classified based upon their level of effectiveness against different types of microbes: Treatment include bacterial endospores, which form a 3-layer coat of protection, and acid-fast Mycobacteria which have a waxy cell wall.
Highest level of resistance
Microbial control (reduction and elimination) methods can be classified based upon their level of effectiveness against different types of microbes: Treatment include protozoans in both cyst and vegetative form, Gram-negative bacteria, which have an outer membrane, porins and drugs pumps, as well as fungi, which have a cell wall made of chitin.
Intermediate level resistance
Microbial control (reduction and elimination) methods can be classified based upon their level of effectiveness against different types of microbes: Treatment include naked viruses, Gram-positive bacteria, and enveloped viruses.
Low level resistance
Microbes that grow best at cooler temperatures ranging from -5°C to 20°Celsius.
Psychrophiles and psychrotrophs
Microbes that include most disease-causing forms of bacteria, grow best at temperatures ranging from 20°C to 40°C.
Mesophiles
Microbes that include bacteria growing in hot springs and deserts, prefer warmer temperatures ranging from 40°C to 80°C.
Thermophiles
Microbes that can be found in geysers and volcanoes, grow best at temperatures above 80°C.
Hyperthermophiles
Moist heat methods
Steam sterilization (Autoclaving, boiling, pasteurization)
Utilizes steam to penetrate cells, is faster and more effective than dry heat.
Moist heat
A high pressure chamber that utilizes temperatures of121°C for 15 minutes under 15 psi (pressure) to sterilize nonliving surfaces (kills endospores). Used to sterilize heat-resistant materials, such as glassware, surgical dressings, rubber gloves, metallic instruments, liquids, and some heat-resistant papers and plastics.
Autoclave
Autoclave temperature
121C for 15 min under 15psi
A low-pressure steam method that requires temperatures of 100°C for a minimum of 10 minutes in order to disinfect, but NOT STERILIZE, objects. Exposing materials to this for 30 minutes will kill most non-spore-forming pathogens, but NOT ENDOSPORES. Used to disinfect drinking water, eating utensils, food, hospital bedding and baby bottles.
Boiling
Used to disinfect drinking water, eating utensils, food, hospital bedding and baby bottles.
Boiling
Used to sterilize heat-resistant materials, such as glassware, surgical dressings, rubber gloves, metallic instruments, liquids, and some heat-resistant papers and plastics.
Autoclave
Boiling temp and time
100C for 10min
A low-pressure, moist heat method used to reduce the number of microbes in MILK and JUICE in order to slow the rate of food spoilage. Milk is not sterile after this, as this techniques kills most microbes that cause human disease and food spoilage, but not all.
Pasteurization
Batch (historical) pasteurization temp and time
63C for 30min
Flash pasteurization temp and time
72C for 15sec
Ultrahigh-temperature pasteurization temp and time
134C for 1sec
Ultrahigh-temperature sterilization temp and time
140C for 1-3sec
Dry heat methods
Incineration (bacti-cinerator)
Sterilization ovens
An effective sterilizing agent because it can denature structural and regulatory proteins needed for metabolism. Used for water-sensitive materials such as metals, oils, and powders.
Dry heat
Because dry heat penetrates more slowly than moist heat (steam), dry heat ovens require higher temperatures and longer exposure times in order to effectively sterilize objects.
Dry heat temp and time?
1 hour at 171°C or
2 hours at 160°C
another effective dry heat method, which uses temperatures of 800°C to 6500°C to burn microbial material.
Incineration
Preferred method for disposing of animal carcasses contaminated with infectious agents.
Incineration
Example of microbes that can survive several months in refrigerator.
Psychrophiles
Staph aureus
Clostridium
T or F: refrigeration and freezing do NOT kill microbes.
True, they merely hold the number of microbes steady (static). Although refrigeration and freezing can slow or halt the growth of most mesophiles, it may allow the slow growth of spoilage bacteria, such as psychrophiles that can grow and metabolize even at freezing temperatures!
Danger zone that allows microbes to rapidly grow and metabolize.
Temperatures between 20-50C
Ionizing radiation
Gamma rays
X-rays
A powerful, penetrating form of radiation that causes breakages in microbial DNA.
Ionizing radiation
Radiation that is Used to regulate the growth of microbes in food, drugs, vaccines, medical plastics, surgical gloves, bone and skin tissue grafts
Ionizing radiation
Main advantage of ionizing radiation
Ability to penetrate and sterilize material thru outer packages ad wrappings
Main disadvantage of ionizing radiation
Risk of exposure for those who work with this type of radiation.
Non-ionizing radiation example
Uv radiation
A form of non-ionizing energy with a short wavelength (4-400nm). It kills microbes by damaging their DNA.
UV radiation
UV damaged DNA forms ____ that block DNA replication and transcription.
pyrimidine (thymine) dimers
UV damaged DNa can be repaired by a process called ____.
Photoreactivation
Photoreactivation uses visible light (_____nm) to activate repair enzymes (pyrimidine or thymine dimerase or DNA photolyase) that repair the UV damaged DNA.
400-750nm
radiation that can be used to regulate the growth of microbes on non-living substances, such as: food, water, on walls and floors, even the air in dental offices and hospital operating rooms.
Non-ionizing radiation (UV radiation)
Disadvantage of UV radiation
Unable to penetrate thru substances such as glass, metal and plastic.
Exposure of human tissue to UV light can result in …
UVA (wrinkles)
UVB (sunburn)
UVC (cancer)
process used to disinfect or sterilize gases and heat-sensitive liquids by physically removing microbes. It mechanically traps and removes microbes, but does not kill them and cannot remove some of the toxins they produce. Used to sterilize water, air, blood products, vaccines, drugs, IV fluids, enzymes and media. Surgical masks and respirators filter the air that healthcare workers inhale and exhale.
Filtration
Filters pores size used to remove bacterial cells
0.22-0.45 um
Filters pores size used to remove viruses
0.01-0.22 um
Filters pores size used to remove smallest
0.01 um
Filters pores size used to remove larger viruses and pliable bacteria (mycoplasma, rickettsia, chlamydia, some Spirochetes)
0.025 um
Filters pores size used to remove largest viruses and most bacteria
0.22 um
Filters pores size used to remove largest bacteria
0.45 um
Filters pores size used to remove Protozoa and small unicellular algae
1.2 um
Filters pores size used to remove yeasts and larger unicellular algae
3 um
Filters pores size used to remove multicellular algae, animals and fungi
5 um
A mechanical method of microbial control used to remove microbes from the surface of instruments and teeth. It utilizes high frequency sound waves to generate “shock waves” that are conducted through living structures or liquids. The force exerted by these shock waves leads to the rupture of microbial membranes and their removal from surfaces. Used to clean surgical instruments, dental instruments, teeth, pacemakers, hearing aids, test tubes and small electronics.
Ultrasonic vibration
Chemical control method that can only eliminate some types of bacteria, fungi and viruses. These agents are generally used to clean materials that contact outer, but not inner, skin surfaces.
Low-level disinfectants
Chemical control method that can kill fungal spores (sex cells) and acid-fast bacteria (TB), but cannot kill endospores. These agents are typically used to treat materials that come into contact with mucous membranes.
Intermediate-level disinfectant
Chemical control method that are able to kill endospore-forming bacteriaand can be used to completely eliminate all microbes on non-living surfaces. These powerful agents are used to sterilize materials such as catheters, implants, and surgical instruments.
High-level disinfectant
High level disinfectant kills endospores.
Some
Intermediate level disinfectant ___ in killing mycobacteria and non lipid viruses, but does NOT kill endospores
Varies
Chemical agents of control have 4 primary sites of action:
1) cell wall;
2) cell membrane;
3) proteins;
4) NA (DNA or RNA).
Depending on ______ used, chemicals from these groups (SCHHAAPPP) can be used as sterilants, disinfectants, and antiseptics.
Concentration and form (gas, liquid or solid)
Gas or vapor form of a chemical agent (aldehyde, halogen, H2O2)
Sterilants
Liquid form of chemical agent
Disinfectant
Much lower concentration than sterilants and disinfectants
Antiseptics
Iodide (skin antiseptic, betadine surgical scrub)
chlorine gas (sterilant); chlorine bleach (high level disinfectant)
bromine
fluorine (toothpaste and water disinfectant)
Halogens
chemicals that alter microbial proteins and at high concentrations and in gas form can be sporicidal
Halogens
Lysol, pine-sol, antibacterial soaps and products that contains triclosan
Phenol and phenol derivatives
aromatic compounds that are toxic to tissues in high concentrations. They are intermediate to low-level disinfectants and antiseptics that damage cellular membranes and alter protein structure. They are bactericidal, fungicidal and virucidal, but CANNOT kill ENDOSPORES.
Phenol and phenol derivatives
low-level disinfectants used in hospitals, dental offices, and veterinary clinics. They can also be used as skin degerming agents in preoperative scrubs or oral rinsed. It disrupts cellular membranes (surfactants) and denatures proteins, but cannot kill endospores.
Chlorhexidine
residual chemicals that remain active on surfaces for extended periods of time, providing longer-lasting antimicrobial effects.
Chlorhexidine
Hibiclens,hibitane, betasept, peridex
Chlorhexidine
intermediate-level disinfectants or antiseptics that dissolve lipid membranes (surfactants) and denature proteins. They are effective against most fungi and bacterial cells, but CANNOT kill endospore- formers.
Alcohols
Alcohols are most effective in concentrations ranging from _____.
50-90%
70% ethanol (disinfectants)
50% isopropanol (antiseptics)
Water-free Hand sanitizer such as purell
Alcohols
It produces highly reactive free radicals that damage proteins and DNA. It is most toxic to anaerobes, which lack the enzyme catalase needed for its breakdown. It is one of the 3 chemical groups that can be used to kill endospores.
Hydrogen peroxide s
Peroxides can be used as sterilants (\_\_\_ peroxide vapor), high-level disinfectants (\_\_\_ solutions) or as antiseptics (\_\_\_ solutions).
sterilants (30% peroxide vapor)
high-level disinfectants (25% solutions)
antiseptics (3% solutions).
It is cationic quaternary ammonium compounds called “quats.”
Soap and detergent
weak disinfectants or antiseptics that act as surfactants to disrupt the cellular membranes of some bacteria and fungi. It is unable to kill endospore-forming bacteria.
Soap and detergents (quats)
Laundry detergent (benzalkonium chloride)
Dish soap
Household cleaners (409)
Mouthwash. (Cetylpyridinium chloride)
Soap and detergents
Copper,zinc, mercury and silver Gold and silver lining of the teeth Thimerosal (vaccine preservative) Silver nitrate eye drops Zicam Mercury chlorides
Heavy metals
can be used as low-level disinfectants or antiseptics. They are NOT sporicidal. They oxidize and inactivate proteins and can be toxic to humans
Heavy metals
highly toxic agents which can be used as sterilants, high-level disinfectants, or tissue preservatives depending upon concentration and form (gas, liquid or solid). It inhibits microbial growth by damaging proteins and nucleic acids (DNA and RNA). It can be used to kill endospores and inactivate viruses during vaccine preparation.
Aldehydes
2% glutaraldehyde solution (cidex)
37% formaldehyde
Aldehydes
static agents used to prevent food spoilage.
Preservatives
organic acids, sulfur compounds,nitrites, and sugars and salts.
Preservatives
added to baked goods, cheeses, pickles, sodas, jams, jellies and dried fruits to reduce the growth of mold and bacteria.
Organic acids
Sorbic, benzoic, propionic, lactic, acetic (vinegar), ascorbic
Organic acids
prevent the growth of molds in dried fruits, juices, syrups and wines and prevent discoloration of food products.
Sulfur compounds (sulfites)
used in cured meats (ham, bacon, hot dogs, bologna, salami) to maintain a bright red color. These substances break down during frying and freezing, causing the meat to lose its “pink” appearance. There has been a link between nitrosamines produced from the cooking of processed meat and cancer in humans.
Nitrites and nitrates
Sugar and salts
Natural preservatives
can be used to create hypertonic environments, which cause microbial cells to shrink and undergo plasmolysis due to the loss of water. These preservatives are static agents, because they do not kill microbes, they only slow or inhibit their metabolism.
Natural preservatives
