controlling microbes

what is sterilization

a process that destroys or removes all viable microorganisms (including viruses)

what are some agents that preform sterilization

* Heat (autoclaving)
* Sterilants (certain chemical agents)

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what is the disinfection

a physical process or a chemical agent to destroy vegetative pathogens but not bacterial endospores. It removes harmful products of microorganisms (toxins) from material

what are some agents of disinfection

* Bleach
* Iodine
* Heat (boiling)

what decontamination/sanitization

a cleansing technique that mechanically removes microorganisms as well as other debris to reduce contamination to safe levels

what are some agents of decontamination/sanitization

* Soaps
* Detergents
* Commercial dishwashers

what is antisepsis/degermation

a process that reduces the number of microbes on the human skin. A form of decontamination but on living tissues

what are some agents of antisepsis/degermation

* alcohol
* surgical hand scrubs

what are some common uses of sterilization

* Surgical instruments
* Syringes
* Commercially packaged foods

what are some common uses for disinfection

* Food utensils
* Applying 5% bleach solution to an examining table
* Immersing thermometers in an iodine solution between uses

what are some common uses for decontamination/sanitization

* Cooking utensils
* Dishes
* Bottles
* Cans

what does the root -cide mean

having the capacity to kill

what is the definition of sepsis

the growth of microorganisms in the blood and other tissues

what does the term asepsis refer to

any practice that prevents the entry of infectious agents into sterile tissues and therefore prevents infection

what is a antiseptic substance

a growth-inhibiting agent used on tissues to prevent infection

when is antiseptics agents used

to destroy or inhibit pathogens of exposed body surfaces (skin and mucous membranes), wounds, and surgical incisions

what does the words ‘stasis’ and ‘static’ mean

to stand still

what are critical medical devices

devices that are expected to come into contact with sterile tissues. These must be sterilized before use.

Ex: a syringe needle, or an artifical hip

what are semicritical devices

devices that come into contact with mucosal membranes. These must receive at least high-level disinfection and preferably should be sterilized

Ex: an endoscopy tube

what are noncritical items

devices that do not touch the patient or are only expected to touch intact skin. These require only low-level disinfection unless they become contaminated with blood or body fluids

Ex: blood pressure cuffs or crutches

what is the microbiological definition of death

the permanent loss of reproductive capability, even under optimum growth conditions

what influences the action of antimicrobial agents (definitely want to remember these)

* The number of microorganisms. A higher load of contaminants requires more time to destroy
* The nature of the microorganisms in the population. In most actual circumstances of disinfection and sterilization, the target population is not a single species of microbe but a mixture of bacteria, fungi, endospores, and viruses, presenting a broad spectrum of microbial resistance
* The temperature and pH of the environment
* The concentration (dosage, intensity) of the agent. For example, ultraviolet (UV) radiation is most effective at 260 nanometers (nm), and most disinfectants are more active at higher concentrations
* The mode of action of the agent. How does it kill or inhibit the microorganism
* The presence of solvents, interfering organic matter, and inhibitors. Saliva, blood, and feces can inhibit the actions of disinfectants and even of heat

what is an antimicrobial effect on cells called

its mode (or mechanism) of action

what are the 4 cellular targets physical and chemical agents effect

* the cell wall
* the cytoplasmic membrane
* cellular synthetic processes (DNA and RNA)
* Proteins

what is the cellular target of detergents

* cell wall
* cytoplasmic membrane

what is the cellular target of chemicals

the cell wall

what are the cellular targets of alcohol

* the cell wall
* cytoplasmic membrane
* proteins

what is the cellular target of formaldehyde and ethylene oxide

cellular synthesis

what are the cellular targets of moist heat and phenolics

proteins

what are the two broad categories of controlling microorganisms

physical and chemical

what property does elevated temperatures (exceeding the maximum growth temperature) possess

microbicidal properties

what property does lower temperatures (below the minimum growth temperature)

microbistatic

what does the temperature of moist heat usually range from

60°C to 135°C

what does the temperature of dry heat usually range from

160°C to several thousand degrees Celsius

what is the advantage of moist heat in relation to dry heat

it can achieve the same effectiveness but with lower temperatures and shorter exposure times

how does dry heat effect the cell

it removes the water necessary for metabolic reactions and denatures proteins

what happens at very high dry heats

the heat oxidizes the cells, burning them to ashes

what is required for the destruction of endospores

temperatures above boiling

what is thermal death time (TDT)

the shortest length of time required to kill at 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 are the 3 moist heat methods

* Boiling water
* Pasteurization
* Steam under pressure: autoclaving

what are the applications of boiling water

useful in the home for disinfection of water, materials for babies, food and utensils, bedding, and clothing from the sickroom

what are the applications for pasteurization

milk, wine, beet, other beverages

what are the applications for steam under pressure: autoclaving

heat-resistant materials such as glassware, cloth (surgical dressings), metallic instruments, liquids, paper, some media, and some heat-resistant plastic.

what is pasteurization

a technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquids flavor and nutritional value.

what are the 2 dry heat methods

incineration and hot-air oven

what are the applications of incineration

bunsen burners/small incinerators: laboratory instruments such as inoculating loops. Large incinerators: syringes, needles, culture materials, dressings, bandages, bedding, animal carcasses, and pathology samples

what are the applications of hot-air oven

glassware, metallic instruments, powders, and oils that steam does not penetrate well. Not suitable for plastics, cotton, and paper, which may burn at the high temperatures, or for liquids, which will evaporate

what is the principal of cold treatment

to slow down the growth of cultures and microbes in food during processing and storage

is the cold a microbicidal process

nope, it can only be counted as microbistatic

what does the term desiccated mean

to become dry throughly and gradually (the example given in the text was vegetative cells directly exposed to normal room air for a long period)

why is desiccation a valuable way to preserve foods

because it greatly reduces the amount of water available to support microbial growth

what happens in the process of lyophilization

pure cultures are frozen instantaneously and exposed to a vacuum that rapidly removes the water (its goes straight from the frozen state into the vapor state, skipping the liquid state altogether). This method avoids the formation of ice crystals that would damage the cell, thus allowing the preservation of microorganisms

what is radiation

energy emitted from atomic activities and dispersed at high velocity through matter of space

what are the two methods of radiation

* Ionizing radiation: gamma rays and X rays


* Non ionizing radiation: Ultraviolet rays (UV)

what are the applications of ionizing radiation

drugs, vaccines, medical instruments (especially plastics), syringes, surgical gloves, tissues such as bone and skin, and heart valves for grafting

what are the applications of UV rays

reducing postoperative infections, preventing transmission of infections by respiratory droplets, and curtailing the growth of microbes in food-processing plants and slaughterhouses

how does UV radiation damage cells

by causing the inappropriate formation of bonds between two adjacent bases on a DNA strand

what is filtration effective at

removing microbes from air and liquids

what are modern microbiological filters like

thin membranes of cellulose acetate, polycarbonate, and a variety of plastic materials (Teflon, nylon) whose pore size can be carefully controlled and standardized

why do very small pore filters permit true sterilization

because they can remove microbes and VIRUSES, some even remove larger proteins

how is a sterile liquid typically prepared

by suctioning the liquid through a sterile filter into a presterilized container

when is filtration used

to prepare liquids that cannot withstand heat, including serum and other blood products, vaccines, drugs, IV fluids, enzymes, and media

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