Micro ch 5

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

10

Typical conditions used for sterilization are

121°C at 15 psi for 15 minutes.

Your brother goes on to explain the concept of decimal reduction (D-value) time to you. To illustrate his point, he tells you that if the D-value for Giardia was 3 minutes and the starting number of cells was 104, the time it would take to eliminate all of the Giardia cells would be

15 minutes

If a process kills 90% of the organisms per minute, how many minutes would it take to kill all organisms when starting with 100,000 organisms?

6 minutes

You tell Jasmine that it is important that she use a sterile instrument to pierce Paul's boil. Jasmine does not know what "sterile" means or why she needs to use something sterile for her "boil surgery," so you explain. Select the best answer.

A sterile instrument is free of all microbes, endospores, and viruses. Jasmine needs to use a sterile blade because it will come into contact with Paul's tissues, and is thus a critical instrument.

Which of the following is (are) considered when selecting a germicidal chemical?

All of the choices are correct Toxicity Cost Compatibility with the material being treated Environmental impact

Microbial death rates may be affected by

All of the choices are correct. (PH, temp, presence of organisms, growth of biofilm)

Chemical germicides

All of the choices are true. ( may react irreversibly with proteins/ enzymes, may react with cytoplasmic membranes or viral envelopes, may be disinfecting or even sterilizing, are sensitive to dilution factor, time of contact, and temp of use)

1) Lister developed his ideas on prevention of infection during medical procedures after studying the work of

B) Pasteur.

Please select the TRUE statement regarding preservation of perishable products.

Bacterial resistance to some of the chemicals included to perishable products has been reported.

Chlorine

Can be used effectively as an antiseptic

Please select the INCORRECTLY matched pair.

D-value - time to destroy 10% of microbes present.

Ultraviolet radiation at the bacterial wavelength destroys bacteria by

Damaging nuclei acid

Which are essentially

Dry 200ºC heat for 1.5 hours; wet 121ºC heat for 15 min

Which of the following are resistant to destruction by typical disinfection methods?

Endospores of Bacillus and Clostridium

100% ethanol is twice as effective as 60% ethanol at controlling bacteria

FALSE

Cold and freezing are very effective in killing bacteria

FALSE

Dry heat takes a much shorter time to sterilize material that wet heat.

FALSE

Heat treatment is effective method for sterilization or disinfection of all materials

FALSE

Hydrogen peroxide may be used as a sterilant on living tissue

FALSE

Pasteurization results in the sterilization of food products.

FALSE

Prions are easily destroyed by common sterilization procedures

FALSE

The endospores of Pseudomonas make that organism very difficult to kill

FALSE

To reduce or eliminate disease-/spoilage causing organisms, food is often subjected to

Heat, chemical additives, radiation, and cold

The autoclave treatment may not be monitored by

Heat-sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus

The most important function of nitrites in processed foods is to

Inhibit the germination of Clostridium botulinum endospores

You tell Jasmine that there are various ways that she can in fact sterilize the knife she plans to use. Which of the following is unlikely to be available to Jasmine for sterilizing her knife in her home?

Irradiating the knife with gamma rays.

Chlorhexidine

Is extensively used for antiseptics

Glutaraldehyde

Is very good for use on heat-sensitive medical items

Which of the following statements is FALSE regarding Giardia?

It has a peptidoglycan cell wall.

Select the FALSE statement regarding hydrogen peroxide

It immediately kills all bacteria when applied to a wound

Hand washing with plain soap is very effective in controlling spread of microorganisms because

It is very effective at the mechanical removal of microorganisms

Which is true of iodine?

It's usually found as tinctures or iodophors

Which of the following is/are not (a) sterilization method(s)?

Pasteurization

A common environmental organism that may even grow in certain chemical disinfectants is

Pseudomonas aeruginosa

Hexachlorophene has been particularly effective against

Staphylococcus aureus

At the end of your conversation with Jasmine, you tell her that the best course of action for her and Paul is to go to the clinic and have the boil treated there. A boil is a serious infection and the risks of trying to treat it at home are just too great.

TRUE

Boiling is very effective at removing most common waterborne pathogens

TRUE

Generally, heavy metals, except silver, have been proven to be too toxic for use on human tissue and are no longer used medically.

TRUE

Organic acids, such as benzocaine acid, are often added to foods to prevent microbial growth.

TRUE

The more bacteria one starts with, the longer it will take to kill them.

TRUE

Upon heat treatment, bacteria die at a constant proportion.

TRUE

Which is true of nosocomial infections?

They are acquired by susceptible people in the hospital.

Which of the following methods sterilize the materials?

Ultrahigh-temperature (UHT) method

Your brother tells you that most likely you ingested Giardia cysts that were in the stream water. He says you should have treated the water before you drank it. Which of the following would NOT have been a possible way for you to do this, as a hiker?

Using high pressure processing.

Gamma irradiation

can be used to either sterilize or pasteurize, depending on the dose of radiation

One of the first chemicals used by Lister to prevent surgical infections was

carbolic acid

Quaternary ammonium compounds are

cationic detergents that help wash surfaces.

A suffix used to describe a killing action would be

cidal

A common application of dry heat in the microbiology laboratory is to

d) sterilize the inoculating loop

Phenolics

denature proteins and destroy cytoplasmic membranes.

Commercial canning processes

destroy Clostridium botulinum spores, are especially needed on low acid foods AND are 12D processes (designed to kill 1012 endospores).

Upon treatment with heat or chemicals, bacteria will

die at a constant proportion.

Generally, membrane filters are not used to remove

enzymes from liquids.

Boiling is not reliable for sterilization because

heat resistant endospores are unaffected

Oxidation of proteins is achieved most readily

in a hot air oven

Moist heat kills microorganisms by

irreversible denaturation of proteins

Pasteurization

is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level.

Ethylene oxide is gas that

is very useful for sterilizing heat or moisture sensitive items AND is potentially carcinogenic.

Liquid media containing heat-sensitive components would best be sterilized by

membrane filtration

A sterile item is free of

microbes, endospores, and viruses

Alcohols are not reliably effective at destroying

non-enveloped viruses AND endospores

Silver sulfadiazine, a combination of silver and sulfa drug, is used to

prevent infection of second- and third-degree burns.

Gamma rays cause biological damage in living systems by

producing reactive molecules such as superoxide and hydroxyl free radicals

Which would be most effective against Pseudomonas?

radiation

The process of killing or removing all of the microorganisms in or on a material is called

sterilization

Jasmine tells you she plans to wash her hands with soap and water before working on Paul's boil, to get rid of all the bacteria on her skin and prevent the possibility of Paul getting an infection. You tell her

that washing and scrubbing with soap is generally sufficient to control microbes in routine situations but that soap itself does not destroy many organisms. Jasmine should try to get some sterile gloves.

Microwaves do not kill organisms directly but kill by

the heat they generate in a product

Compounds of tin, Mercury, arsenic, and copper are no longer used to prevent microbial growth in cooling water primarily because

their use contributes to serious pollution of natural waters

You ask your brother which method of eliminating microbes is the best in general. He tells you that there is no one perfect method and that various factors must be taken into account when considering any antimicrobial approach. These include all of the following EXCEPT

whether a potential infection can be easily treated.e