Chapter 9

Practical Matters in Microbial Control (cont'd) •Substances that require sterilization: 2 •Considerations for sterilization: 3

-Durable solids to sensitive liquids -Situations requiring sterilization confront persons involved in health care -Cost -Effectiveness -Method of disposal

Radiation •Energy emitted from atomic activities and dispersed at high velocity through matter or space: 3

-Gamma rays -X rays -Ultraviolet radiation

Agents vs. Processes (cont'd) •_____: chemical agents applied directly to exposed body surfaces (skin and mucous membranes), wounds, and surgical incisions to prevent vegetative pathogens: -Preparing the skin before surgical incisions with iodine compounds -Swabbing an open root canal with hydrogen peroxide -Ordinary hand washing with a germicidal soap

Antiseptics

Chemical Agents inMicrobial Control •Occur in the liquid, gaseous, or solid state •Range from disinfectants and antiseptics to sterilants and preservatives •____ _____: chemicals dissolved in pure water as the solvent •_______:chemicals dissolved in pure alcohol or water-alcohol mixtures

Aqueous solutions Tinctures

Heat Resistance and Thermal Death: Endospores and Vegetative Cells •______ _____ -Exhibit greatest resistance -Destruction of spores usually requires temperatures above boiling -Resistance varies •______ ____: -Vary in sensitivity to heat-Death times vary from 50°C for 3 minutes to 60°C for 60 minutes

Bacterial endospore Vegetative cells

Agents vs. Processes •Sterilization and disinfection: processes •_____: chemical that destroys bacteria except for those at the endospore stage •_____: chemical that can kill fungal spores •_____: chemical known to inactivate viruses, especially on living tissue •_____: an agent capable of destroying bacterial endospores •_______:chemical agents that kill microorganisms

Bactericide Fungicide Virucide Sporicide Germicide/microbicide

Practical Matters in Microbial Control •______ ___ ____: -Expected to come into contact with sterile tissues -Must be sterilized before use •_______ _____: -Come into contact with mucosal membranes -Must receive high-level disinfection •_____ ____ -Do not touch the patient or only touch intact skin -Require only low-level disinfection

Critical medical devices Semicritical devices Noncritical devices

Microbial _____ •______:permanent termination of an organism's vital processes: -Microbes have no conspicuous vital processes, therefore death is difficult to determine -Permanent loss of____ _____, even under optimum growth conditions has become the accepted microbiological definition of death.

Death reproductive capability

The Effects of Cold and Desiccation (cont'd) •____: -Vegetative cells directly exposed to normal room temperature gradually become dehydrated. -Some microbes are killed by desiccation; on others desiccation has no effect •______: -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.

Desiccation Lyophilization

Factors Affecting the Germicidal Activity of Chemicals (cont'd) •Chemical Strength or Concentration -______:a small volume of the liquid chemical is diluted in a larger volume of solvent to achieve a certain ratio -_____ ___ _____: used for solutions such as chlorine that are effective in very diluted concentrations -______ ______: solute is added to water by weight or volume

Dilutions Parts per million Percentage solutions

Mode of Action and Relative Effectiveness of Heat (cont'd) •____ ___ -Dehydrates the cell, removing water necessary for metabolic reactions -Denatures proteins-Increases the stability of some protein conformations, requiring higher temperatures -At very high temperatures, oxidizes cells, burning them to ashes

Dry heat

Other Antimicrobial Agents:Dyes, Acids, and Alkalis •_____: -Active against gram-positive bacteria and fungi -Limited application because they stain and have a narrow spectrum of activity •____ ___ _____: -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

Dyes Acids and Alkalis

________ •Effective method to remove microbes from air and liquids: -Fluid is strained through a filter with openings large enough for the fluid to pass, but too small for microbes. -Also used are thin membranes of cellulose acetate, polycarbonate, and plastics whose pore size is carefully controlled. -Charcoal, diatomaceous earth, or unglazed porcelain are also used. -Pore sizes can be controlled to permit true sterilization by trapping viruses or large proteins.

Filtration

Modes of Action ofAntimicrobial Agents •Antimicrobials have a range of cellular targets: -___selective agents tend to be effective against the_____ range of microbes (heat and radiation). -Selective agents target only a___ cellular component (drugs). •Cellular targets of physical and chemical agents: 4

Least widest single -Cell wall -Cell membrane -Cellular synthetic processes -Proteins

Factors Affecting the Germicidal Activity of Chemicals (cont'd) •_____ ____ ____ -Most compounds require adequate contact time to allow the chemical to penetrate and act on microbes present. •_____ ___ ___ ___ ____ -Smooth, solid objects are more reliably disinfected than those with pores or pockets. -Large amounts of organic material can hinder penetration. -Adequate cleaning of instruments and other reusable materials must precede the use of a germicide or sterilant.

Length of Exposure Composition of Material Being Treated

Mode of Action and Relative Effectiveness of Heat •_______ ____ -Operates at lower temperatures and shorter exposure times to achieve the same effectiveness as dry heat -Microbicidal effect is the coagulation and denaturation of proteins

Moist heat

Selecting a Microbicidal Chemical (cont'd) •Noncorrosive or nonstaining properties •Sanitizing and deodorizing properties •Affordability and ready availability •___ ____ can completely fulfill all of these requirements: -Glutaraldehyde and _____ ____ approach this ideal.

No chemical hydrogen peroxide

________ _____ •Adding large amounts of salt or sugar to foods creates a hypertonic environment for bacteria, causing plasmolysis. •Pickling, smoking, and drying foods have been used for centuries to preserve foods. •Osmotic pressure is never a_____ technique.

Osmotic Pressure sterilizing

Selecting a Microbicidal Chemical •_____action, even in low concentrations •Solubility in water or alcohol and ____ ___stability •Broad-spectrum action without being toxic to human and animal tissues •Penetration of inanimate surfaces to sustain a cumulative or persistent action •______ to becoming inactivated by organic matter

Rapid long-term Resistance

Agents vs. Processes (cont'd) •____: the growth of microorganisms in the blood and other tissues •____: -Any practice that prevents the entry of infectious agents into sterile tissues and thus prevents infection -_____ ____: practiced in healthcare; range from sterile methods to antisepsis

Sepsis Asepsis Aseptic techniques

Agents vs. Processes (cont'd) •___ & ___mean "to stand still." •______:chemical agents that prevent the growth of bacteria on tissues or on objects in the environment •_______:chemicals that inhibit fungal growth •Antiseptics and drugs often have______ effects because microbicidal compounds can be toxic to human cells. •Even______ agent doesn't necessarily result in sterilization, depending on how it is used. Practical

Stasis and static Bacteristatic Fungistatic microbistatic a -cidal

Thermal Death Measurements •_____ ____ ___: shortest length of time required to kill all test microbes at a specified temperature •_____ _____ _____ the lowest temperature required to kill all microbes in a sample in 10 minutes •Heat treatment of perishable substances must render the product free of agents of spoilage or disease without affecting the speed and cost of processing

Thermal death time (TDT) Thermal death point (TDP):

Factors Affecting Death Rate (cont'd) •The______ (dose, intensity) of the agent: -UV radiation is most effective at 260 nm -Most disinfectants are more active at higher concentrations. •The mode of____ of the agent: -How does it kill or inhibit the microorganism? •The presence of____, interfering organic matter, and inhibitors: -Saliva, blood, and feces can inhibit the action of disinfectants and even the action of heat

concentration action solvents

Selecting a Microbicidal Chemical (cont'd) •Germicides are evaluated in terms of their effectiveness in_____ microbes in medical and dental settings: -High-level germicides kill_____ and can be used as______. -Intermediate-level germicides kill_____, but not bacterial _____, resistant____, and____. -Low-level germicides eliminate only _____ bacteria, vegetative_____ cells, and some_____.

destroying endospores sterilants fungal spores pathogens viruses vegetative fungal viruses

Filtration (cont'd) •Used to prepare liquids that cannot withstand____ such as serum, blood products, vaccines, drugs, IV fluids, enzymes, and media •Alternative method for decontaminating milk and beer without altering its flavor •Important step in water purification •Unable to remove soluble molecules (toxins) that can cause disease •____ ____ ___ ___ filters are used in hospital rooms and sterile rooms.

heat High efficiency particulate air (HEPA)

Factors Affecting Death Rate •Death of the whole population is not_______: -Begins when a certain_____ of microbicidal agent is met. -Death continues in a______ manner as the time or concentration is increased. -______cells tend to die more quickly than_____ metabolically active cells. -Eventually, a point is reached at which survival of any cells is highly unlikely; this point is equivalent to______.

instantaneous threshold logarithmic Active less sterilization

Methods of Physical Control: Heat •Elevated temperatures are____. •Lower temperatures are_____. •___ ___: hot water, boiling water, or steam between 60°C and 135°C •______ ____: hot air or an open flame, which ranges from 160°C to thousands of degrees Celsius

microbicidal microbistatic Moist heat Dry heat

Factors Affecting the Germicidal Activity of Chemicals •Nature of the_____ being treated •Nature of the____ being treated •Degree of_____ •Time of_____- •______and______ action of the germicide

microorganisms material contamination exposure Strength chemical

Factors Affecting Death Rate (cont'd) •The_____ of microbes -Higher load of contaminants takes longer to destroy •The_____ of the microorganisms in the population -Target population is usually a mixture of bacteria, fungi, spores, and viruses •_____ and____ of the environment

number nature Temperature pH

The Effects of Cold and Desiccation •Principal benefit of cold treatment is to ___ ___ of cultures and microbes in food during processing and storage: -Cold merely____ the activities of most microbes. •Most microbes are not adversely affected by gradual cooling, long-term refrigeration, or deep-freezing. •Temperatures from -70°C to -135°C can____ cultures of bacteria, viruses, and fungi for long periods.

slow growth retards preserve

Endospores and Vegetative Cells (cont'd) •Vegetative cells of______ have the same susceptibility to heat as vegetative cells of _________ •Pathogens have the same susceptibility to heat as______. •____,_____, & ____are similar in their sensitivity to heat. •_____are resistant to heat; tolerance extends from 55°C for 2 - 5 minutes to 60°C for 600 minutes.

sporeformers, non-sporeformers. nonpathogens Fungi, protozoa, and worms Viruses

Relative Resistance of Microbial Forms •Primary targets of microbial control are microorganisms capable of causing infection or spoilage in the environment or on the human body: -The targeted population often contains mixtures of microbes with extreme differences in resistance and harmfulness. -Bacterial endospores have traditionally been considered the most resistant microbial entities. •The goal of any______ process is the destruction of bacterial endospores: -Any process that kills endospores will invariably kill all less resistant microbial forms.

sterilization