CH 11

3. Define -static and -cidal. Compare the action of microbicidal and microbistatic agents, providing an example of each.

-static: to stand still. a microorganism's reproduction and growth can be INHIBITED by depriving it of water, nutrients, or a suitable temperature -cidal: to kill microorganisms can be KILLED by disrupting their metabolism, structural integrity, or their means of reproduction

10. Describe three factors that affect the actions of a germicide

1. NATURE of MATERIAL being treated 2. DEGREE of CONTAMINATION 3. TIME of EXPOSURE 4. STRENGTH & CHEMICAL action of the germicide

4. Name four categories of cellular targets for physical and chemical agents.

1. The cell wall: Chemical agents can damage the cell wall by blocking its synthesis or digesting the cell wall. Example: Chemicals, detergents, and alcohol. 2. The cell membrane: Agents physically bind to lipid layer of the cell membrane, opening up the cell membrane and allowing injurious chemicals to enter the cell and important ions to exit the cell. Example: Detergents. 3. Cellular synthetic processes (DNA, RNA): Agents can interrupt the synthesis of proteins via the ribosomes, inhibiting proteins needed for growth and metabolism and preventing multiplicantion. Agents can change genetic codes (mutation). Examples: Formaldehyde, radiation, and Ethylene oxide. 4. Proteins: Some agents are capable of denaturing proteins (breaking of protein bonds, which results in breakdown of the protein structure). Agents may also attach to the active site of a protein, preventing it from interacting with its chemical substrate. Examples: Moist heat, alcohol and phenolics.

7. Differentiate between two types of radiation control methods, providing an application of each

1. ionizing radiation: if the radiation ejects orbital electrons from an atom, it causes ions to form (gamma rays, x rays, high-speed electrons). Radiation ejects orbital electrons from an atom, causing ions to form. Causes the most damage to proteins. COLD sterilization is used for materials sensitive to heat or chemicals. Breaks DNA. 2. Nonionizing radiation: exemliefied by ultraviolet, excites atoms by raising them to a higher energy state, but it does not ionize them. Leads to the formation of abnormal bonds within molecules such as DNA and is source of mutations. Excites atoms, raising them to higher energy state. Leads to the formation of abnormal bonds (pyrimidine dimers) within molecules such as DNA (T-T or C-C)

2. Identify the types of microorganisms that are most resistant and least resistant to control measures.

1. prions 2. protozoan cysts 3. fungal spores 4. gram pos. bacteria

6. Put the following in order from most resistant to least resistant: a. Fungal spores b. Protozoan cysts c. Gram positive bacteria d. Prions

1. prions 2. protozoan cysts 3. fungal spores 4. gram pos. bacteria

9. Describe four desirable qualities of a germicide.

1. rapid action in low concentrations 2. solubility in water or alcohol and long-term stability 3. broad-spectrum microbicidal action without toxicity to human and animal tissues 4. penetration of inanimate surfaces to sustain a cumulative or persistent action 5. resistance to becoming inactivated by organic matter 6. noncorrosive or nonstaining properties 7. sanitizing and deodorizing properties 8. affordability and ready availability

4. Explain four different methods of moist heat control

1. steam under pressure: autoclave. Pressure cooker. 121 degrees C and 15 psi. surgical equipment. 2. nonpressurized steam: tyndallization (cannot withstand high temps of autoclave)free flowing steam in chamber for 30-60 min for 3 days. 3. pasteurization: heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquids flavor and food value. Disinfection of beverage. Heat is applied to liquids to kill potential infectious agents. Do not kill endospores 4. Boiling water; 100 degrees C. only disinfecting something.

6. Identify advantages and disadvantages of cold treatment and desiccation

Advantage: slow growth of cultures and microbes in food during processing and storage. Some microbes are killed by cold temps but most are not adversely affected by gradual cooling long-term refrig or deep freezing. Desiccated: dehydrated. What happesn to vegetative cells in room air. Many die out in normal temps but some can withstand long periods of desiccation. Desiccation can be a valuable way to preserve foods bc it greatly reduces the amount of water available to support microbial growth.

1. Name the desirable characteristics of chemical control agents.

Affects cell walls, cytoplasmic membranes, proteins or DNA; often more effective against enveloped viruses and vegetative cells of bacteria, fungi and protozoa

9. What are the four cellular targets of physical and chemical agents

Cell wall, cell membrane, cellular synthetic processes (DNA, RNA), protein

5. Explain two methods of dry heat control

Incineration: in a flame or electric heating coil 1,87 degrees C, furnaces and incinerators 800- 6500 degrees C, used for needles, beeding, tissue samples, could kill endospores. Bunsen burner is an example used for loops/needles

2. Discuss several different halogen agents and their uses in microbial control.

Iodine inhibits protein function and is a strong oxidizing agent; chlorine forms the strong oxidizing agent hypochlorous acid, which alters cellular components; iodine and chlorine may act alone or as components of inorganic and organic compounds

2. Compare and contrast moist and dry heat methods of control, and identify multiple examples of each.

Moist heat: hot water, boiling water, or steam. 60 degrees C- 135 degrees C. operates at lower temperatures and shorter exposure times to achieve the same effectiveness as dry heat.

1. Distinguish among the terms sterilization, disinfection, antisepsis, and decontamination.

Sterilization-refers to any process that eliminates, removes, kills, or deactivates all forms of life and other biological agents Disinfection-killing, inhibition, or removal of pathogenic microorganisms antisepsis-Prevention of infection by inhibiting or arresting the growth and multiplication of germs Decontamination-the process of cleansing an object or substance to remove contaminants

6. Define the term surfactant, and explain this antimicrobial's mode of action

Surfactants which are molecules with hydrophilic and hydrophobic regions which lodge into membranes and break them down Mode of action: cell membrane

3. List advantages and disadvantages to the use of phenolic compounds as control agents

The advantages of phenolic compounds is that they remain one standard against which other (less toxic) phenolic disinfectants are rated. The disadvantage is that phenolic compounds are toxic, which makes them dangerous to use as antiseptics.

14. Ultraviolet radiation produces ________ dimers

pyridimine

14. List two acids used in food preservation

lactic acid & sorbic acid

8. Identify applications for ethylene oxide sterilization.

Ethylene oxide is used to disinfect plastic materials and delicate instruments. It can also be used to sterilize syringes, surgical supplies, and medical devices that are prepackaged.

10. True/False: Lower temperatures can be used with dry heat than moist heat.

False

8. Outline the process of filtration and describe its two advantages in microbial control. Explain how filtration functions as a control method.

Filtrations: effective method ot remove microbes form air and liquids. A fluid is strained through a filter with openings large enough for the fluid to pass through but too small for microorganims to pass through. Used to prepare liquids that cannot withstand heat, inlcuind gserum and other blood products, avvines, drugs, IV fluids, enzymes, and media. Alternative method for decontaminating milk and beer without altering flavor. Water purification. Removes airborne contaminates that are a common source of infection and spoilage.

7. Discuss the advantages and disadvantages of aldehyde agents in microbial control

Glutaraldehyde is somewhat unstable with increased pH and temperature, and formaldehyde is extremely toxic and irritating to skin and mucous membranes

1. Name six methods of physical control of microorganisms

Heat, radiation, filtration, ultrasonic waves, cold, abrupt changes in environment, drying, osmotic pressure, desiccation (dehydrate)

4. Explain the mode of action of alcohols and their limitations as effective antimicrobials

mode of action: cell wall or proteins. their limitations: intermediate level

9. Identify some common uses of osmotic pressure as a control method.

Osmotic pressure: preserving food. Adding large amounts of salt or sugar to foods creates a hypertonic environment for bacteria in the foods, causing plamoylsis and making it impossible for bacteria to multiple. Meats are cured. High surag concentration in foods like jelly.

11. The lowest temperature required to kill all of the microbes in a sample in 10 minutes is the _____ _____ _____.

Thermal death point

3. Define thermal death time and thermal death point, and describe their role in proper sterilization

Thermal death time (TDT) - the shortest time required to kill all test microbes at a specified temp Thermal death point (TDP)- the lowest temp required to kill all microbes a sample in 10 minutes

12. True/False: Cold merely retards the growth of most microbes

True

5. ________ is disinfection on a living surface

antispesis

7. Describe the difference between a bactericidal agent and a bacteristatic agent

bactericidal refers to killing bacteria; bacteriostatic inhibits the growth of bacterial cells

8. List and describe four factors that affect microbial death rate.

cidal-kills bacteria static- stops the movement of bacteria -number of microbes -presence of organic matter in human wastes -temperature -fats and proteins -pH -time of exposure to agent -specific characteristics of the microorganism

5. Pinpoint the most appropriate application of hydrogen peroxide agents.

contact lens disinfection low temperature sterilizing cabinets for colonoscopes wound cleansing

12. True/False: Phenol is still extensively used as a disinfectant.

false

13. True/False: Filtration is not a method of sterilization.

false -even smaller pore diameters permit true sterilization by removing viruses and even large proteins

13. True/False: A higher concentration of alcohol is more effective than a lower concentration

false; 70% is most effective

11. The most extensively used of all chlorine compounds is _________.

hypochlorites