ch 5

A suffix used to describe a killing action would be

-cidal

In a one D process, how many D values would it take to reduce a population of 10^10 cells to one survivor

10

Typical conditions used for sterilization are

121C at 15 psi for 15 min

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

6 minutes

Commercial canning processes

Are geared to destroy Clostridium botulinum spores, are especially needed on low acid foods AND are 12D (designed to kill 10^12 endospores) processed

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 which help wash surfaces AND are attracted to the negative charge on the microbial cell surface

Ultraviolet radiation at the bactericidal wavelength destroy bacteria by

Damaging nucleic acid

Phenolics

Denature proteins and destroy cytoplasmic membranes, remain effective in the presence of detergents or organic material, AND phenolics such as triclosan, have been used widely in various lotions and soaps

Upon treatment with heat or chemicals, bacteria will

Die at a constant proportion

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

Endospores of Bacillus and Clostridium. Pseudomonas. Naked viruses. Mycobacterium spp. All of the choices are correct

Generally, membrane filters are not used to remove

Enzymes

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 than wet heat

False

Heath treatment is an 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 and viroids are easily destroyed by common sterilization procedures

False

The endospores of Pseudomonas make that organism very difficult to kill

False

Boiling is not reliable for sterilization because

Heat resistant endospores are unaffected

The autoclave treatment may be monitored by

Heat sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus

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

Heat. Chemical additive. Radiation. Cold. All of the Above

Moist heat kills microorganisms by

Irreversibly coagulation of proteins

Chlorhexidine

Is a member of the biguanides AND is extensively used in antiseptics

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

Glutaraldehyde

Is, if given enough time, able to destroy all forms of microbial life AND is very good for use on heat-sensitive medical items

Which of the following is true of hydrogen peroxide?

It is a sterilant for inanimate objects and is quickly inactivated on living tissue; it is broken down by catalase into water and oxygen AND it is even more effective when used in combination with per acetic acid

Chemical germicides

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 temperature of use. All choices are true.

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

Membrane filtration

A steril item is free of

Microbes, endospores AND viruses

Alcohols are not reliably effective at destroying

Naked viruses AND endospores

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

Pasteur

Which of following is not a sterilization method?

Pasteurization

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

Prevent infection of surgical wounds

Gamma rays cause biological damage in living systems by

Producing reactive molecules such as superoxide and hydroxyl free radicals

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

Pseudomonas Aeruginosa

Which would be most effective against Pseudomonas?

Radiation

Hexachlorophene has been particularly effective against

Staphylococcus aureus

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

Sterilize the inoculation loop

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

Sterlization

Commands 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

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

Toxicity. Cost. Compatibility with the material being treated. Environmental impact. All of the above

Boiling is very effective at removing most common waterborne pathogens

True

Gernerally, 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 benzoic acid, are often added to foods to prevent microbial growth

True

Upon heat treatment, bacteria die at a constant proportion

True

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

True

Which of the following methods sterilize the materials?

Ultrahigh-temperature (UHT) method

Plain soap is very effective in controlling spread of microorganisms because it is

Very effective at the mechanical removal of microorganisms

In order to speed up the sterilization process, which of the following would be useful?

Washing/mechanical removal of bacteria/organic matter

Nosocomial infections

are acquired while in the hospital AND occur because of a susceptible population and presence of disease causing organisms

Which are essentially equivalent treatments?

dry 200C heat for 1.5 hours; wet 121C heat for 15 minutes

Oxidation of proteins is achieved most readily

in hot air over

The most important function of nitrites in processed foods is to

inhibit the germination of clostridium botulinum endospores

Which is true of iodine?

it does not readily kill endospores. It may be used as an antiseptic or as a disinfectant It is important to use it at the recommended dilution It is usually found as tinctures of iodophors All of the choices are correct.

Microbial death rates may be affected by

pH. Temperature. The presence of organics. All of the choices are correct.

Chlorine

readily reacts with organics to produce potentially carcinogenic trihalomethane AND is an effective, inexpensive, disinfectant able to destroy all types of microorganisms

Microwaves do not kill organisms directly bu kill by

the heat they generate in the product