Microbiology-CH 11

6 methods of the physical control of microbes were discussed... · Heat

Dry Heat- Air with a low moisture content heated by a flame or electric coil. Lack of water increases stability of some protein configurations, necessitating higher temperatures; at high temperatures, dry heat oxidizes cells, burning them to ashes. Moist Heat- Hot water, boiling water, steam, autoclave; operates at lower temps and shorter times and denaturing proteins.

If provided an example such as "I have a liquid that becomes inedible when heated, but I want to control the growth of microbes in to make it more shelf stable. What method could I use to achieve this goal?", you should be able to narrow your list of choices down to an effective method.

Filtration

6 methods of the physical control of microbes were discussed... Filtration

Filtration: Fluid is strained through a filter with openings large enough for liquid to pass through, but too small for microbes to pass through. Allows selection of the minimum particle size to be trapped. Even smaller pore diameters permit true sterilization by removing viruses and even large proteins.

Provide 2 examples to how these elements are used to control microbial growth?

Gold and Silver. Silver Nitrate- topical germicide Silver ion- incorporated into hard surfaces and textiles, like toilet seats.

How do halogens act as disinfectants?

Halogens are strong oxidizers which means they steal electrons from reducing processes.

Why is determining microbial death a harder metric to determine than the death of other organisms, like animals?

Harder to detect that macroscopic organisms, no conspicuous vital signs, and loss of movement cannot be used to indicate death.

How do heavy metals kill microbes?

Heavy metals effectively bind and inactivate proteins.

Which level of germicide would be recommended for prepping tools for surgery? For disinfecting electrodes?

High-level germicides are recommended for surgical tools and low-level germicides are recommended for disinfection electrodes.

What type of chlorine compound is found in household bleach?

Household bleach is a weak solution of sodium hypochlorite.

How could you improve the germicidal properties of soap?

If soap is combined with chlorhexidine or iodine, making it more germicidal.

What type of iodine compound is used today as a skin antiseptic?

Iodophors are the iodine compound commonly used in skin antiseptic techniques.

What are some practical concerns of microbial control that should be considered before choosing what method to use?

Is the control method suitable for a given application? Will the agent penetrate to the necessary extent? Is the method cost and labor-efficient, and is it safe?

6 methods of the physical control of microbes were discussed... Osmotic Pressure

Osmotic Pressure: Addition of large amounts of salt or sugar to foods to create hypertonic environments. Causes plasmolysis in bacteria, and impossible for microbes to multiply.

For each of the following phenolic compounds, provide an example of a product that is used that contains the compound. Phenol

Phenol- is the first major antimicrobial chemical used, has toxic and irritating side effects.

For each of the following phenolic compounds, provide an example of a product that is used that contains the compound. Phenolics

Phenolics- act as cellular poisons, by disrupting cell walls and membranes and precipitating proteins (they are hydrophobic)

Explain how time, starting microbial population, type of microbe, & type of agent can all drastically change how effective microbial control will be?

Presence of solvents, interfering organic matter, and inhibitors, ph, concentration of agent... all these factors take a part in the effectiveness of microbial control. Microbes grow rapidly so time in essential as well as concentration of the agent you are preforming with if its strong enough to disinfect or sterilize, etc.

Order from most resistant to least: prions, gram(+) bacteria, gram(-) bacteria, enveloped viruses, naked viruses, and endospores.

Prions, endospores, gram(-), non-enveloped, gram(+), and enveloped.

6 methods of the physical control of microbes were discussed... Radiation

Radiation: Gamma rays, x-rays, and UV rays, etc. are emitted from atomic activities and dispersed at high velocity through matter or space. Irradiation- bombardment of microbes with radiation Ionizing Radiation- radiation that ejects orbital electrons from an atom, causing ions to form; causes damage to most proteins. Nonionizing Radiation- Excitement of atoms, raising them to a higher energy state; leading to the formation of abnormal bonds within molecules such as DNA. UV Radiation- Not as penetrating as ionization; passes through air, slightly through liquids, and poorly through solids. The object to be disinfected must be directly exposed to it for full effect. Forms pyrimidine dimers.

Provide three examples of historical control of microbes.

Salting, pickling, and smoking.

Ethyl alcohol is a cheap & effective method for control microbial growth on skin. However, it has a limitation in that it can evaporate quickly. How long should hand sanitizer remain "wet" on hands for adequate antisepsis to have occurred?

Sanitizer should at minimum 30 seconds.

Research the class of compounds used in Listerine that give them their antibacterial properties.

Some active ingredients are cetylpyridinium chloride, chlorhexidine, essential oils, fluoride, and peroxide.

What are the potential drawbacks to the use of heavy metals for controlling microbial growth?

Some drawbacks of heavy metals are toxicity to humans if ingested, allergic reactions, neutralization by biological wastes, and microbes can develop resistance.

Describe a negative consequence for the use of antimicrobial chemicals in household products.

Some negatives are that they are very toxic, not all destroy endospores, and explosive.

Four outcomes of microbial control outside of the body.

Sterilization, decontamination: sanitization, antisepsis, and disinfection.

Understand the differences between sterilization, disinfection, & antisepsis & be able to identify examples that belong to each group.

Sterilization- the process that destroys or removes all viable microorganisms, including viruses. Sterilization of surgical instruments, commercially packaged foods. Disinfection- the use of physical process or a chemical agent to destroy vegetative pathogens but not bacterial endospores. Using bleach, boiling food, immersing thermometers in iodine. Antisepsis- the practice of preventing the entry of infectious agents into sterile tissues and prevents infection. Swabbing open root canals with hydrogen peroxide, hand-washing, and iodine swabs before incisions.

What four types of halogens are used as disinfectants?

The four types of halogens are chlorine, fluorine, iodine, and bromine.

At what concentration are alcohols most effective?

The greatest efficacy is 70-95%.

What are some medical concerns of microbial control that should be considered before choosing what method to use?

The type of contacts each sterilized medical device is contacting and or permanently attached to. Will affect certain membranes?

What is a potentially harmful effect of repeated inhalation/exposure to isopropyl alcohol?

The vapors affect the nervous system metabolizing to acetone becoming lethal in small amounts.

Explain thermal death point & thermal death time.

Thermal Death Point- is the lowest temperature required to kill all microbes in samples in 10 minutes. Thermal Death Time- is the shortest length of time required to kill all test microbes at a specified temperature.

For the aldehydes & gaseous sterilants discussed, can you explain how these chemicals kill microbes?

These can disinfect inanimate objects by being an organic substance with -CHO group making them strong reducers.

Why are soaps considered low-level/weak germicides? How do they perform their action?

They are mainly only used for mechanical removal of microbes, and pseudomonas grows abundantly in soap dishes.

List 3 desirable qualities of a germicide.

Three desirable qualities of germicides are rapid action in low concentrations, penetration of inanimate surfaces to sustain a cumulative or persistent action, and noncorrosive or non-staining properties.

What traits about the chemical structure of alcohols make them good at disrupting cell membranes?

Alcohol breaks the bonds in between hydrophobic and hydrophilic molecules and destroying vegetative forms of microbes, but not endospores.

For each of the following phenolic compounds, provide an example of a product that is used that contains the compound. Bisphenols

Bisphenols- bisphenol A (BPA) is added to some plastics as an antimicrobial measure.

Compare & contrast decontamination & sterilization.

Both are techniques of mechanically removing microbes and debris. Decontamination reduces contamination to safe levels, and sterilization destroys and removes all viable microorganisms, including viruses.

What is the difference between a tincture & an aqueous disinfectant?

Both tinctures and aqueous solutions are antimicrobial chemicals. Tincture- is antimicrobial chemicals dissolved in pure alcohol or water-alcohol mixtures. Aqueous Disinfectants- are solutions containing pure water as the solvent.

What are the four cellular targets of physical/chemical methods for microbial growth?

Cell wall- breakdown, digestion, making cell fragile to lysis. Cell or Cytoplasmic membrane- disruption of selection permeability. Cellular synthetic processes- substances that inhibit DNA or RNA polymerization or interfere with their structure. Proteins- disruptions of proteins by denaturing/changing shape or blocking protein synthesis.

Understand their definitions.

Cidal means kill, and static means prevention of growth.

6 methods of the physical control of microbes were discussed... Cold

Cold: Treatment that slows the metabolic activities of most microbes; some microbes can be killed; most are not affected by cold treatments.

Hydrogen peroxide can be used as a disinfectant, antiseptic, & sterilant. How does this chemical kill cells?

Concentrated enough it still can harm tissue by overwhelming our catalase for healing wounds. It is active oxygen and it takes electrons.

For each of the following phenolic compounds, provide an example of a product that is used that contains the compound. Cresols

Cresols- Lysol is a low-level disinfectant

Research how long bleach should sit on a surface to assure proper disinfection. The answer will be either 1 minute, 5 minutes, 10 minutes, or 20 minutes.

Depending on the microbe, bacteria, etc. but typically at least 15 minutes or more.

6 methods of the physical control of microbes were discussed... Desiccation

Desiccation: Dehydration of vegetative cells directly exposed to normal room air. This treatment preserves foods because it reduces the amount of water available to support microbial growth.

For each of the following phenolic compounds, provide an example of a product that is used that contains the compound. Diphenols

Diphenols- Triclosan, is an example of one added to many products.