Chapter 5 Homework Quiz

Which of the following is NOT a sterilization method?

Pasteurization

Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperature.

False

Match the term to its description to test your understanding of the use of moist heat to control microbial growth. Commercial canning Pasteurization Steam under pressure

-Commercial canning: Requires use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes. -Pasteurization: Heat applied to beverages to prevent spoilage and kill pathogens. High-temperature-short-time protocols include holding liquids at 72°C for 15 sec. Does not sterilize. -Steam under pressure: Uses an autoclave called a retort to destroy the endospores of Clostridium botulinum. It will not destroy the endospores of some thermophiles.

Use the terms provided to complete the sentences in order to test your understanding of the difference between: 1. sterilants 2. high-level disinfectants 3. intermediate-level disinfectants 4. low-level disinfectants

1. Germicides known as _____ can destroy all microbes including both bacterial endospores and all types of viruses. 2. _____ disinfectants destroy all viruses and vegetative cells but will not kill endospores. 3. _____ disinfectants destroy vegetative cells and some, but not all, viruses. They are unable to kill endospores even when used for a prolonged period of time. 4. Germicides known as _____ disinfectants kill vegetative cells except for mycobacteria and are unable to destroy non-enveloped viruses and endospores.

Match the descriptions and antimicrobial agents to the appropriate type of germicide to test your knowledge of: 1. Halogens 2. Quaternary ammonium compounds 3. Alcohols 4. Phenolic compounds

1. Halogens: -Common disinfectant which oxidizes proteins and other cell components. -Chlorine, chlorine dioxide, iodine 2. Quaternary ammonium compounds: -Cationic detergent which can be safely used on food preparation surfaces. -Compound reacts with membranes to destroy many vegetative bacteria and enveloped viruses. -These compounds are ineffective against mycobacteria, naked viruses and Pseudomonas species. 3. Alcohols: -Aqueous solutions which can kill vegetative bacteria and fungi but not bacterial endospores or naked viruses. -Solutions can be used as antiseptics or to disinfect instruments and surfaces without leaving a residue. -Ethanol or isopropanol 4. Phenolic compounds: -Germicidal agent which can leave an antimicrobial residue after use. -Carbolic acid

Match each type of radiation with its description. 1. Ionizing radiation 2. Ultraviolet radiation 3. Microwaves

1. Ionizing radiation: Doesn't affect microorganisms directly, but can generate heat in fluids which can indirectly kill microbes. 2. Ultraviolet radiation: Not very penetrating radiation. Easily stopped by interfering materials. Works by producing thymine dimers in DNA strands. Most effective at close range and with long duration of exposure. 3. Microwaves: High energy radiation that directly destroys DNA and damages cytoplasmic membranes. It can also cause indirect damage by producing reactive oxygen species (ROS).

Match the important points regarding selection of an appropriate germicide with the description/rationale that fits it best. 1. Cost and availability 2. Compatibility with the material being treated 3. Toxicity 4. Activity in the presence of organic matter 5. Storage and Stability

1. Some germicides are highly effective, but are rare and/or expensive. 2. Some substances are negatively affected by treatment with some germicides (i.e. corrosives damaging metals/rubber). 3. All germicides are somewhat harmful to humans and the environment. This parameter identifies HOW harmful the chemical is. 4. Some germicides may become less efficient when used in/on areas with organic matter. 5. Some germicides may lose efficiency over time, or may be required in very large amounts that would make them impractical for frequent applications.

In a one D process, how many D values would it take to reduce a population of 1010 cells to one survivor?

10

Match each of the following items that may influence the selection of an antimicrobial procedure with its correct description/rationale. 1. Environmental conditions 2. Type of microbe 3. Composition of the item 4. Risk for infection 5. Number of microorganisms -Different materials respond differently to control measures. Some may even be destroyed by certain methods, preventing their use. -Items that may come into direct contact with body tissues are more likely to cause serious infections if contaminated. -Certain microbes are highly resistant to killing methods (e.g. endospores). -Dirt, grease, and bodily fluids in/on an area can interfere with control methods, as can temperature, pH, and even humidity levels. -It takes longer to kill a large number of microbes than a small number.

2, 5, 1, 4, 3

Please match the term with its description to test your understanding of microbial control terminology. 1. Decontamination 2. Preservation 3. Disinfection 4. Sterilization -Destruction of all microbial life -Reduction of most microbial life on inanimate surfaces -Mechanical removal of most microbes from living or inanimate surfaces -Slows microbial growth but does not reduce the number of existing microbes.

4, 3, 1, 2

The decimal reduction time is the time it takes to kill 90% of a given bacterial population under certain conditions. If 90% of a population of 100,000 bacteria is killed in 10 minutes, how long would it take to reduce the population to 10 cells?

40 minutes

Sterilization is the destruction of all living microbes from a surface by physical or chemical means.

False

Categorize the given medical instruments. Critical Semi-critical Non-critical

Critical: -Scalpel -Needles -Venous catheter Semi-critical: -Gastrointestinal endoscope -Endotracheal tube -Oral Thermometer Non-critical: -Stethoscope -Blood pressure cuff

Select the statements about ionizing radiation that are true. (NOTE: Please change all question marks to checkmarks for correct answers or empty boxes for incorrect answers.)

It can be used to sterilize medications It can be used to sterilize medical equipment -It can be used to reduce spoilage organisms on food

Which of the following about heat treatment is FALSE?

It produces toxic byproducts

This figure is displaying the same information twice—a D value related to logarithmic killing of microbes. Place the tags on the correct areas to identify a) what the D value is and b) what it means. Not all labels are used.

Log decrease of 1 Log decrease of 1 "D"

Place the labels into the correct columns for moist heat and dry heat.

Moist heat: -Boiling -Pasteurization -Autoclaving -Denatures proteins -more efficient -Used to treat drinking water -Used to prevent food spoilage -Used to sterilize microbial media -Used to sterilize surgical instruments Dry heat: -less efficient -incineration -dry heat ovens -Used to destroy medical wastes -Used to destroy animal carcasses -burns cell components -bunsen burner

Match the listed objects and compounds with the appropriate method used to destroy microbes and viruses on/in them.

Moist heat: -Heat-sensitive medications -Milk products Dry heat: -Medical waste -Culture media -Inoculating loop -Animal carcasses Radiation: -Meat products

The more bacteria present on or in something, the longer it takes to kill them all.

True

Moist heat primarily destroys microbes by

denaturing their proteins