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
