Micro Lecture Chemical and Physical Control

true or false: alcohol at the 100% concentration is more effective than a 70% solution of alcohol in killing microbes

False

lyophilization

a combination of freezing and drying that preserves microorganisms and other cells in a viable state for many years.

for what reasons would we want to use a microbicidal agent? a microbistatic?

a microbicidal agent is used when we are sterilizing an environment. This is used because it kills all viable microorganisms, allowing for a sterile environment and for sterile aseptic techniques. This is great in healthcare and hospital settings to prevent infection. A microbistatic agent would be used to temporarily inhibit reproduction of microorganisms. This would be used for sanitization and degermination because it cannot kill but may interrupt and stop/slow down the reproduction of the microorganism. Washing your hands, clothes, body, etc., helps interrupt microorganism reproduction.

autoclave

a pressure-temperature device that can subject pure steam to pressures greater than 1 atmosphere. It is used by health and commercial industries for sterilizing objects.

pasteurization

a technique of applying heat to consumable liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquid's flavor and food value.

a surgical mask is what type of microbial control? (be specific)

air filtration

name one chemical for which the general rule that a higher concentration is more effective is NOT true. why?

alcohol, because at a concentration of 95% or higher there is little to no water which is needed for protein coagulation to occur. So actually, at 70% alcohol (30% water), alcohol shows a greater microbicidal activity.

TDP

also called thermal death point, it is the lowest temperature required to kill all microbes in a sample in 10 minutes.

TDT

also called thermal death time, it is the shortest length of time required to kill all test microbes at a specified temperature.

can something be almost sterile? explain.

an object cannot be slightly sterile or almost sterile, it is either sterile or not sterile. Either it is free of all microorganisms, or it still has microorganisms. There is no in between

germicide

any chemical agent that kills pathogenic microorganisms and can be used on inanimate (nonliving) materials or on living tissue, but it cannot kill resistant microbial cells.

sanitization

any cleansing technique that removes debris, soil, microorganisms, and toxins, and in this way reduces the potential for infection and spoilage.

sterile

any material that has been sterilized (a process that destroys or removes all viable microorganisms, including viruses).

asepsis

any practice that blocks the entry of infectious agents into sterile tissues and thus prevents infection.

which will ensure sterile conditions?

autoclaving

list the three categories of microbial control.

bacteriostatic agents, fungistatic agents, and many antiseptics and drugs are used to control microorganisms in the body and have an microbistatic effect because microbicidal can be toxic.

how does bleach kill?

bleach works as a disinfectant by destroying vegetative pathogens on inanimate objects, but it is unable to kill bacterial endospores. Bleach is diluted because it is a salt (sodium/hypochlorite) with an ionic bond. So if you don't dilute the bleach, you can't separate the sodium from the hypochlorite. The hypochlorite is what actually kills, so without dilution (5% bleach works best), bacteria cannot be killed by bleach.

antiseptic

chemical agents that are applied directly to exposed body surfaces (skin and mucous membrane), wounds, and surgical incisions to destroy or inhibit vegetative pathogens.

chemical surfactants kill microbes by

coagulating proteins and dissolving membrane lipids

how does alcohol kill bacteria? does it work on viruses?

concentrations of 50% and higher dissolve membrane lipids, disrupts cell surface tension, and compromises membrane integrity. Alcohol that enters the protoplasm denatures proteins through coagulation, but only in alcohol-water concentrations of 50% to 95%. Absolute alcohol (100%) dissolves cell membranes and inhibits cell growth but is generally not a protein coagulant (no water is present). Alcohol can however destroy resistant vegetative forms, including tuberculosis bacteria and fungal spores, provided the time of exposure is adequate. Alcohol tens to inactivate enveloped viruses more readily than non-enveloped viruses because of the surfactant effect on the envelope.

what is the cellular targets of detergents?

detergents are molecules that act as surfactants. Most anionic detergents have limited microbicidal power. This includes most soaps. Much more effective are positively charged (cationic) detergents, particularly the quaternary ammonium compounds (quats). It disrupts the cell membranes of sensitive microbes. After a few minutes the cell will burst and die.

any process that destroys the non-endospore-forming contaminant on inanimate objects is:

disinfection

in medicine, how do we use filtration for microbial control? give at least 3 examples.

filtration removes microbes from air and liquids. A fluid is strained through a filter with openings large enough for the fluid to pass through but too small for microorganisms to pass though. Modern microbial filters are thin membranes of cellulose acetate, polycarbonate, and a variety of plastic materials (Teflon, nylon) whose pore size can be carefully controlled and standardized. Ordinary substances such as charcoal, diatomaceous earth, or unglazed porcelain are also used in some applications. Viewed microscopically most filters are perforated by very precise, uniform pores that can very in diameter (coarse at 8µm to ultrafine at 0.02µm). Those with an even smaller pore size permits true sterilization by removing viruses, and even some large proteins. This can be either disinfection or sterilization for liquids, and disinfection only for air because that is hard to filter all of it leading to microorganisms still slightly remaining.

explain how the following can affect germicidal action: -nature of the material being treated -the degree of contamination -the time of exposure -the strength and action

for the nature of material that is being treated we look at if it's porous or non-porous, can it stain, is it living or non-living, etc., which can either make it more or less susceptible to the agents. It the degree of contamination strong or weak determines how effective/quick the agent may work. The time of exposure may tell us how much growth has occurred so we will need to be able to match the correct agent and amount of the agent needed. The strength and action tells us how powerful the agent is and how well it may work. Example: ethanol is more effective at 70% than 95%.

list the three major modes of action for antimicrobial agents.

germicides, disinfectants, and antiseptics are all different modes of action for killing/removing microorganisms. Germicides work on inanimate objects and living tissue, disinfectants work on inanimate objects, and antiseptics work on living tissue. Examples: Lysol, betadine, alcohol. Lysol interferes with proteins and so does betadine, alcohol interrupts the cell envelope and dissolves lipids.

HEPA

high-efficiency particulate air filters that are widely used to provide a flow of sterile air to hospital rooms and sterile rooms.

tyndallization

intermittent sterilization that occurs to selected substances that cannot withstand the high temperatures of the autoclave.

why does a population of microbes not die instantaneously when exposed to an antimicrobial agent?

it all depends on a number of conditions, such as the size of the population, the type of antimicrobial agent, the type of area the population is living on, etc. Death can only begin when a certain threshold of the microbicidal agent (some combination of time and concentration) is met.

why would UV radiation also be dangerous for us?

it can cause sunburn, retinal damage, cancer and skin wrinkling if overexposure on human tissue occurs.

list the physical control methods.

it involves heat and radiation. The heat can either be dry heat or it can be moist heat. Dry heat leads to sterilization and moist heat you usually get disinfection, but can sometimes get sterilization.

explain which level os disinfection is required for the following applications: -items with endospores -electrodes -catheters -thermometers -implants -items with TB -items that may have viruses -respiratory tubes -otoscopes -furniture

items with endospores= sterilization electrodes= sterilization catheters= sterilization thermometers= disinfection implants= sterilization items with TB= sterilization items that may have viruses= disinfection respiratory tubes= sterilization otoscopes= disinfection furniture= disinfection

bactericidal means:

kills microbes by inflicting irreversible damage to the cell

rank the following organisms in order from least to most resistant to microbial control methods: vegetative cells, prions, cysts, endospores, fungal spores, hyphae, enveloped viruses, naked viruses, yeasts, trophozoites.

least resistant are bacterial vegetative cells, fungal hyphae, enveloped viruses, and protozoan trophozoites. Medium resistants are protozoan cysts, some fungal spores, and some viruses (naked). Highest/most resistant are prions, and bacterial endospores.

the primary mode of action of nonionizing radiation is to:

make pyrimidine dimers

-static

means to stand still and can be used in combination with various prefixes to denote a condition.

compare the relative effectiveness of moist vs. dry heat.

moist heat usually occurs at lower temperatures and shorter times. It coagulates and denatures proteins. Dry heat dehydrates the cells (no metabolism but could increase stability, example: endospores), and it alters proteins. It requires higher temperatures, which if they are very high it could oxidize (burn) cells.

does pasteurization sterilize milk? what does it do?

no, pasteurization does not kill all the microbes, it only reduces the microbial load and destroys pathogens. It does this because microbes have the potential to spoil foods and cause illness, so by reducing that number it keeps the food and us safer. The heat used in pasteurization also helps retain the liquid's flavor and food value

your bathroom in a public restroom may say "sanitized for your protection". is sanitization the same as sterilization?

no, sterilization is the destruction/removal of all visible microorganisms, including endospores, while sanitization is the reduction in microorganisms. Sanitization is not able to kill off microbes, it can only reduce the number of microbes.

the primary action of dry heat is to:

oxidize molecules

cooking utensils are often __________ between uses.

sanitized

what is the difference between a tincture and an aqueous solution? why is either used for a chemical germicidal agent? how is it possible for a tincture chemical to still have germicidal action even if the chemical itself has no antimicrobial properties?

solutions containing pure water as the solvent are termed aqueous while tinctures are where the solvent is either pure alcohol or is a water-alcohol mixture. This is because in most cases, solid or gaseous antimicrobial chemicals are dissolved in water, alcohol, or a mixture of the two to produce a liquid solution. Tincture chemicals still have germicidal action because the chemicals toxicity, and it is a mild irritant. The alcohol's mechanism of action depends on its level of concentration: some are able to interfere with the cell membrane, interfere with proteins causing denaturation, and even can even dissolve cell membranes and inhibit cell growth.

compare sterilization, disinfection, and sanitization.

sterilization is the destruction/removal of all viable microorganisms, including endospores. Is very strict terminology. These techniques/methods are often too harsh for the body, but some body parts are already sterile. Disinfection is the physical process or chemical agent that kills vegetative cells but not bacterial endospores. It can remove harmful bacterial products (toxins), and is usually not used on living tissue because it can be toxic to humans and animals too. Examples: 5% bleach, boiling water or utensils, immersing items in iodine between uses. Sanitization is the reduction of the microbial load. Examples: soaps and detergents. It is usually a preferred method to sterilization (cheaper, and cleans too).

why is cold not used to kill microbes?

the cold is used to slow the growth of cultures and microbes in food and other perishable materials during processing and storage. The cold merely slows the activities of microbes, it does not kill majority of them.

sepsis

the growth of microorganisms in the blood and other tissues.

explain how each of these factors affect the rate of microbial death: -number of microorganism -nature of population -temperature and pH -concentration -mode of action -organic matter

the number of microorganisms means the higher the biological load, the more time it will take. The composition of the population is usually a mixed culture, so it will take longer. The temperature and pH of the environment influences death because if it is on the borderline of the microorganisms temperature and pH requirements it might kick off death sooner. Also, if the temperature and pH are at optimum the microorganisms may be more resistant. The concentration/dosage/intensity of the agent could affect the rate. The presence of organic matter, interfering solvents, or inhibitors may affect growth and rate. The mode of action of the agent and how it works affects how quickly it works.

define microbial death.

the permanent loss of reproductive capabilities even under optimum conditions.

degermination

the reduction in microbial load through mechanical means (usually by scrubbing the skin or immersing it in chemicals).

-cidal

the root meaning to kill, and can be combined with other terms to define an antibacterial agent aimed at destroying a certain group of microorganisms.

what are the two types of radiation? why is one unpopular for food due to a consumer misconception?

the two types of radiation are ionizing and non-ionizing. Ionizing radiation causes atoms to release electrons forming ions which consists of z-rays, cathode rays, and gamma rays. This is good for food, seeds, and lab supplies. This causes sterilization. This is the unpopular radiation for food by consumers because they didn't understand that it reduces down to a safe electro-state quickly and thought it was unsafe to eat even though that's not true. Non-ioning radiation excites atoms to a higher state but does not cause them to release an electron. It is non-penetrating and is used on the surfaces of items or work areas, and on water, but is not super effective. This means it causes disinfection.

disinfection/disinfectant

the use of a physical process or a chemical agent to destroy vegetative pathogens but not bacterial endospores, and are normally used on inanimate objects because at concentrations required to be effective, they can be toxic to living tissue.

explain what may result when the following are used to on a microbial population with varied composition of microorganisms. name a use for each. -different types of steam -tyndalization -boiling water -pasteurization -incineration -desiccation -lyophilization

there are two types of steam, pressurized steam and non-pressurized steam. The pressurized steam (autoclave) can kill all microorganisms (sterilize), while the non-pressurized steam can eventually cause sterilization, it just takes a bit longer (intermittent sterilization/tyndallization). Tyndallization is when select substances cannot withstand the high temperatures of the autoclave and kills almost everything, just not spores. By repeating its process over and over, when the spores go back to vegetative cells they will eventually die. Boiling water and pasteurization allow for disinfection because the temperatures and environment/conditions are unable to kill resistant pathogens/cells. Incineration is a dry heat that causes the sterilization of all microorganisms. On the other hand desiccation (dehydration) and lyophilization (freezing and drying) many kill some microorganisms but preserves many other microorganisms by using cold temperatures.

what does TDP stand for?

thermal death point

what are the cellular targets of heavy metals?

they are metallic elements such as mercury, silver, gold, copper, arsenic, and zinc that are applied in microbial control over several centuries. Only preparations containing mercury and silver have any significance as germicides. Although some metals (zinc, iron) are needed in small concentrations as cofactors on enzymes, the higher molecular weight metals (mercury, gold, silver) can be very toxic, even in minute quantities, which is called an oligodynamic action. Mercury, silver, and most other metals exert microbicidal effects by binding onto functional groups of proteins and inactivating them, rapidly bringing metabolism to a standstill.

aside from health care, what other reasons would we have to control microbial number and growth?

to control infections, food and drink spoilages, contamination of research or pharmaceuticals, and detrimental bioremediation or biodegradation.

desiccation

when vegetative cells directly exposed to normal room air gradually becomes dehydrated.

why is it still a bad idea to share alcoholic drinks?

you are therefore sharing bacteria because alcohol concentrations must be 50% or higher to kill bacteria, and no alcoholic beverage is 50% or higher.

list the three major types of control.

1. mechanical- physically removes microbes, but does not kill or inhibit. 2. microbistatic- temporarily inhibits the reproduction of microbes. 3. microbicidal- kills microbes by inflicting irreversible damage to the cells.