ch 11

Question 1

1. What are the 3 main methods of decontamination (broad)?
2. What are the 6 categories of microorganisms that we target?
3. what are the microbes with the highest resistance (2)?
4. what microbes are of moderate resistance (4)?
5. What microbes are of least resistance (4)?
6. What type of virus is the flu? Is it highly resistant?

Answer 1

1. physical, chemical, and mechanical
2. • veg. bacterial cells and endospores
     - fungal hyphae (spores/yeast)
     - protozoan (trophozoites & cysts)
     - worms
     - viruses
     - prions
3. prions and endospores
4. pseudomonas sp, m. tuberculosis, s. aureus, and protozoan cysts
5. vegetative cells, fungal (spores, hyphae, & yeast), enveloped viruses, and protozoan trophozoites
6. enveloped virus low resistance

Question 2

1. …………. is a process that destroys ALL viable microbes, including viruses and endospores. Can only be done on metal equipment.
2. ………….. is a process to destroy vegetative pathogens, not endospores; inanimate objects and surfaces ie patient’s bed
3. ………….. are disinfectants applied directly to exposed body surfaces. Betadine is an example
4. …………….. is any cleansing technique that mechanically removes microbes.

Answer 2

1. Sterilization
2. Disinfection
3. Antiseptic (for bodily surfaces)
4. Sanitization

Question 3

1.- 6. what are the 6 factors that affect microbial death rate?

Answer 3

1. Concentration or dosage of agent
2. Mode of action of the agent
3. Nature of microbes in the population
4. Number of microbes
5. Temperature and pH of environment
6. Presence of solvents, organic matter, or inhibitors

Question 4

1. what is the difference between microbiostatic and microbiocidal?
2. what circumstances would affect the chosen method of microbial control (6)?

Answer 4

1. microbiostatic means the number of cells is held at a stable level whereas microbiocidal means death of microbes
2. • Does the application require sterilization?
     - Is the item to be reused?
     - Can the item withstand heat, pressure, radiation, or chemicals?
     - Is the method suitable?
     - Will the agent penetrate to the necessary extent?
     - cost- and labor-efficient?

Question 5

1. what 4 structures of the cell do antimicrobial agents attack?
2. name the antimicrobial agents that attack the cell wall:
3. name the antimicrobial agents that attack the cell membrane:
4. Name the things that disrupts protein and nucleic acid synthesis:
5. Name the things that denature proteins:

Answer 5

1. the cell wall, cell membrane, synthesis of protein and nucleic acids, and proteins
2. antimicrobial drugs, detergents and alcohol
3. detergents and surfactants
4. chloramphenicol, ultraviolet radiation, formaldehyde
5. alcohols, phenols, acids, heat

Question 6

1. • 5. Name the 5 Methods of Physical control:
2. ………… heat utilizes lower temps and shorter exposure time than ………….
3. ……………. heat utilizes moderate to high temperatures;
4. …………. heat causes coagulation and denaturation of proteins, whereas ………… heat causes dehydration, alters protein structure; incineration
5. how much faster does it take moist heat to sterilize than dry heat (at 121C)?

Answer 6

1. Heat – moist and dry
2. Cold temperatures
3. Desiccation
4. Radiation
5. Filtration
6. moist, dry
7. dry
8. moist, dry
9. at 121C moist takes 15min. Dry takes 600min.

Question 7

1. What is thermal death time (TDT)?

2. What is thermal death point (TDP)?

Answer 7

1. – shortest length of time required to kill all test microbes at a specified temperature
   Variable: time
   Constant: temperature
2. – lowest temperature required to kill all microbes in a sample in 10 minutes
   Variable: temperature
   Constant: time = 10 minutes

Question 8

1. • 2. What are the moist heat methods of control and what are the modes of destruction?
2. What is pasteurization? Is it sterilization?
3. What differs from a batch method to a flash method?

Answer 8

1. Steam under pressure – sterilization. (autoclave) - sterilization 15psi/121C/10-40min.
   Denatures proteins and destroys DNA
2. boiling - 30 min 100 degrees = disinfection (doesn’t destroy spores)
3. heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value. Not sterilization!
4. batch 63-66 C for 30min.
5. 6 C for 15 sec

Question 9

1. what does cold do to microbes? Is this a method to preserve food, media, and cultures?
2. What is desiccation/dehydration, and what happens to the cells? Is it an effective form of microbial control, why or why not?
3. What is Lyophilization? 3. freeze drying; preservation

Answer 9

1. has a microbiostatic effect, yes.
2. Gradual removal of water from cells, leads to metabolic inhibition. Not effective microbial control – many cells retain ability to grow when water is reintroduced
3. 3. freeze drying; preservation

Question 10

1. What is ionizing radiation? Does this achieve sterilization? What types of cells are especially susceptible to this?
2. What types of rays are ionizing?
3. Can ionizing radiation penetrate barriers? What does it do to cells?

Answer 10

1. deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA. Yes, sterilization. Rapidly dividing cells such as microbial colonies
2. Gamma rays, X-rays, cathode rays
3. Yes, breaks DNA

Question 11

1. Describe nonionizing radiation:
2. How does nonionizing radiation work?
3. Where is nonionizing radiation used?

Answer 11

1. UV light that must have direct exposure because it has little penetrating power. Cannot penetrate barriers.
2. UV light creates pyrimidine dimers, which interfere with replication of DNA
3. In the sterilization of air or water surfaces like in a water treatment plant.

Question 12

1. How does filtration work?

2. What is it used for?

Answer 12

1. It is a physical removal of microbes by passing through a filter
2. Used to sterilize heat sensitive liquids and air in hospital isolation units and industrial clean rooms and vaccines.

Question 13

1. What are the chemical agents of microbial control?

2. Name what each level of germicide kills and for what each level necessary:

Answer 13

1. Germicides of high, intermediate, and low levels
2. High level: kills endospores, used on indwelling medical devices like implants. May be sterilants

Intermediate level: kill fungal spores (not endospores), tubercle bacteria, and viruses
Used to disinfect devices that will come in contact with mucous membranes but are not invasive

Low level: eliminate only vegetative bacteria, vegetative fungal cells, and some viruses
Clean surfaces that touch skin but not mucous membranes

Question 14

1. • 4. Name the 4 factors that affect how well germicidal agents work:

Answer 14

1. Nature of the material being treated
2. Degree of contamination
3. Time of exposure
4. Strength and chemical action of the germicide

Question 15

1. …………… act as surfactants. What part of the cell do they act upon? They are …………. level
2. ……….. is one of the oldest and most effective …………… (type of germicide). It acts upon the ………… ………….. of which type of microbes?
3. ………… is iodine combined with alcohol.
4. ……………… is iodine combined with an organic carrier molecule. These are still quite effective, but they are less toxic and do not stain as badly. Betadine is an example.
5. ……………. ………… produces highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to O2 gas. It is toxic to which type of organism? Is it considered antiseptic or sporicidal?

Answer 15

1. alcohols at 70%, cell membrane and coagulation of proteins. intermediate level
2. iodine, antiseptics, cell membrane, all bacteria, endospores, fungi, and viruses.
3. tincture
4. iodophor
5. hydrogen peroxide, anaerobes. Both Antiseptic and sporicidal at 3%, 30% respectively.

Question 16

1. What are quats, how do they work, and what are they classified as?
2. What level do they decontaminate to?
3. Are they positively or negatively charged?
4. Give an example:

Answer 16

1. Quaternary ammonia compounds. They act as surfactants that alter membrane permeability of some bacteria and fungi. Classified as disinfectants.
2. Low level decontamination
3. positively charged
4. clorox sanitizing wipes

Question 17

1. …………. mechanically remove soil and grease containing microbes.
2. How can we increase the antimicrobial capabilities of soap?

Answer 17

1. soaps

2. add germicide to it.

Question 18

1. compare the resistance of endospores to veg cells in the following categories:
   - moist heat
   - radiation
   - sterilizing gas
   - sporicidal liquid

Answer 18

• moist heat: spores = 120C veg cells = 80C (1.5x)
• radiation: spores= 4000 grays veg cells = 1000 (4x)
• sterilizing gas: spores= 1200mg/l veg cells
  = 700mg/l (1.7x)
• sporicidal liquid: spores = 3 hours veg cells = 10min (18x)