Chapter 5 Control of Microbial Growth

Select all the correct statements regarding autoclaving.

-Autoclaving is consistently effective in sterilizing most objects. -Adding pressure to the autoclave increases the temperature of the steam in it. -Biological indicators such as heat resistant endospores are used to ensure that an autoclave is working properly. -Autoclaving involves the use of both temperature and pressure.

Select the statements about ionizing radiation that are TRUE

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

Moist heat primarily destroys microbes by

denaturing their proteins

T/F Handwashing with regular soap removes all normal microbiota from the skin

False

Select the reasons sugar of salt can be used to food preservation. Check all that apply.

-They dehydrate the bacterial cells. -They may cause plasmolysis. -They create a hypertonic environment, unfavorable for growth.

Chlorine is safely used to disinfect waste liquids, some medical instruments, and various surfaces. It is readily available in liquid household bleach bleach must be diluted because high concentrations are toxic and corrosive. To obtain an effective concentration of chlorine when using household bleach, a 1 to 100 dilution is made. This means that _______ ML of bleach is added to ______ ML of water

1.0/99

How many D values would it take to reduce a population of 10^10 cells to one survivor

10

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

40 minutes

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

False

Choose which of the following best describes the difference between a disinfectant and an antiseptic.

Disinfectants are anti-microbial chemicals used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. Antiseptics are anti-microbial chemicals that can be used on skin or tissues to achieve the same result.

Review the chart*. Which bar(s) represent(s) the control in this experiment?

Green (No washing)

Match each type of radiation with its description.

Ionizing Radiation- High energy radiation that directly destroys DNA and damages cytoplasmic membranes. It can also cause indirect damage by producing reactive oxygen species (ROS) Ultraviolet- 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. Microwaves- Doesn't affect microorganisms directly but can generate heat in fluids which can indirectly kill microbes.

Which of the following about heat treatment is false?

It produces toxic byproducts

Match each of the following methods for preservation of perishable products with its description.

Low-temperature storage: - Slows or stops critical enzyme reactions in some (but not all) microorganisms. Reducing the available water: - Additions of sugar or salt, or subjecting the food to a high vacuum environment. Chemical preservatives: - Must be non-toxic. - Weak organic acids such as benzoic or sorbic acids often used. - Nitrate and nitrite can also be used to inhibit germination of endospores of C. botulinum.

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

MOIST heat -Pasteurization -Denatures proteins -More efficient -Used to prevent food spoilage -Used to sterilize microbial media -Used to treat drinking water -Autoclaving -Boiling -Used to sterilize surgical instruments DRY heat -Incineration -Burns cell components -Less efficient -Used to destroy medical wastes -Used to destroy animal carcasses -Dry heat ovens -Bunsen burner

Select the method that would be used to sterilize a liquid containing the heat sensitive compounds vitamin B 12 and human growth hormone.

Membrane filtration

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

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

Which of the following is not a sterilization method?

Pasteurization

Classify the given microbes and infectious agents into sensitive or resistant with regards to effect of anti microbial procedures

SENSITIVE -HIV (enveloped) -Bacillus vegetative cells -Escherichia species RESISTANT -Poliovirus (non-enveloped) -Giardia cysts -Pseudonomas species -Bacillus endospores -Prion -Mycobacteria species

Assuming strict adherence to recommended protocols, which of the following temperature treatments achieves sterilization?

Steam autoclaving

Match the term to its description to test your understanding of the use of moist heat to control microbial growth

Steam under pressure: 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 seconds. Does not sterilize. Commercial canning: Uses an autoclave called a retort to destroy the endospores of clostridium botulinum. It will not destroy the endospores of some thermophiles.

Please match the microbial control term with its description

Sterilization: destruction of all microbial life Preservation: Slows microbial growth but does not reduce the number of existing microbes Decontamination: mechanical removal of most microbes from living or inanimate surfaces Disinfection: Reduction of most microbial life on inanimate surfaces

T/F Sterilization is the destruction or removal of all microbes from a surface by physical or chemical means.

True

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

True

Which of the following is a method of choice for achieving a sufficient level of microbial control in routine day-to-day situation?

Washing and scrubbing with soaps and detergents

What conclusion can you make from the data presented?

Washing your hands with water removes some bacteria, but adding soap is more effective.

Which of the following kills food microbes, rather than just reducing their growth?

irradiation

Boiling is not a reliable method for sterilization because

it does not destroy heat-resistant endospores

When filtering a liquid, it is a bad idea to use a membrane with a pore size smaller than necessary because

the smaller the pore size, the slower the filtration process, so you would be wasting time.