Microbiology Chapter 5 HW
Which of the following about heat treatment is FALSE?
It produces toxic byproducts (correct: fast, reliable, cheap, safe)
Which of the following is/are not (a) sterilization method(s)?
Pasteurization
The process of killing or removing all of the microorganisms in or on a material is called
sterilization
A common application of dry heat in the microbiology laboratory is to
sterilize the inoculating loop
T/F: Aldehydes can be used to disinfect superficial wounds
False
Classify the given microbes and infectious agents into "sensitive" or "resistant" with regards to effect of antimicrobial procedures.
*picture
Place the labels into the correct columns for moist heat and dry heat:
*picture
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.
+
Match each of the following methods for preservation of perishable products with its description: -Reducing the available water -Chemical preservatives -Low-temperature storage
-Additions of sugar or salt, or subjecting the food to a high vacuum environment. -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. -Slows or stops critical enzyme reactions in some (but not all) microorganisms.
Select the correct statements about autoclaving
-Autoclaving involves the use of both temperature and pressure -adding pressure to the autoclave increases the temperature of the steam in it -autoclaving is consistently effective in sterilizing most objects -biological indicators such as heat resistant endospores are used to ensure that an autoclave is working properly
1. What organism was the cause of the outbreak at the Seneca Lake Sprayground? 2. What type of organism caused the outbreak at Seneca Lake Sprayground? 3. True or false: Chlorine treatment is effective in removing Cryptosporidium from water. 4. Cryptosporidium infection results in diarrhea that is self-limiting in healthy people, but in ______ patients, it can produce dehydration through severe diarrhea and can be life-threatening.
-Cryptosporidium -Protozoan -false -infants, elderly, or immunocompromised
Match each of the following items that may influence the selection of an antimicrobial procedure with its correct description/rationale: -Composition of the item -Type of microbe -Risk for infection -Environmental conditions -Number of microorganisms
-Different materials respond differently to control measures. Some may even be destroyed by certain methods, preventing their use. -Certain microbes are highly resistant to killing methods (e.g. endospores). -Items that may come into direct contact with body tissues are more likely to cause serious infections if contaminated. -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.
Which of the following chemicals is/are suspected carcinogens?
-Formaldehyde -Ethylene oxide
Select which of the following might impact the results of this experiment.
-Length of time washing hands -Type of soap -Section of lab floor sampled by each volunteer.
Which of the following would be an example of occupational exposure for a healthcare worker?
-Needle stick -Cut with sharp object such as scalpel. -Contact of mucous membranes with blood
Match each type of radiation with its description: -Ultraviolet radiation -Ionizing radiation -Microwaves
-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. -High energy radiation that directly destroys DNA and damages cytoplasmic membranes. It can also cause indirect damage by producing reactive oxygen species (ROS). -Doesn't affect microorganisms directly, but can generate heat in fluids which can indirectly kill microbes.
Match the term to its description to test your understanding of the use of moist heat to control microbial growth: -steam under pressure -pasteurization -commercial canning
-Requires use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes. -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. -Uses an autoclave called a retort to destroy the endospores of Clostridium botulinum. It will not destroy the endospores of some thermophiles
Identify what investigations would need to be done to eliminate the possibility that patient A contracted hepatitis C by occupational exposure at the facility where she worked.
-Reviewing records for all patients at the facility. -Onsite inspection of the facility for evidence of HCV -Observation of the safety practices used by staff at the facility
Please match the term with its description to test your understanding of microbial control terminology: Preservation Decontamination Sterilization Disinfection
-Slows microbial growth but does not reduce the number of existing microbes. -Mechanical removal of most microbes from living or inanimate surfaces -Destruction of all microbial life -Reduction of most microbial life on inanimate surfaces
Match the important points regarding selection of an appropriate germicide with the description/rationale that fits it best: -Compatibility with the material being treated -Activity in the presence of organic matter -Storage and stability -Cost and availability -Toxicity
-Some substances are negatively affected by treatment with some germicides (i.e. corrosives damaging metals/rubber). -Some germicides may become less efficient when used in/on areas with organic matter. -Some germicides may lose efficiency over time, or may be required in very large amounts that would make them impractical for frequent applications. -Some germicides are highly effective, but are rare and/or expensive. -All germicides are somewhat harmful to humans and the environment. This parameter identifies HOW harmful the chemical is.
Match the germicide with its use.: High-level disinfectant Intermediate-level disinfectants Low-level disinfectant Sterilant
-Used to treat semi-critical instruments such as gastrointestinal endoscopes. -Used to treat non-critical instruments such as stethoscopes. -Used to treat floors, furniture, walls and so on. -Used to treat heat-sensitive critical instruments such as scalpels.
1. What was the most likely mode of transmission of Cryptosporidium at the Seneca Lake State Park Sprayground? 2. True of false: Cryptosporidium was not susceptible to disinfection through filtration and chlorination of the spray park's water supply. 3. What type of radiation in sunlight causes damage to DNA? 4. UV irradiation inactivates Cryptosporidium because it 5. UV water treatment systems are effective in treating
-Water-borne -true -UV radiation -blocks the action of DNA polymerase -bacteria, viruses and protozoans
A suffix used to describe a killing action would be
-cidal
1. UV light causes ______ bonds to form between adjacent thymines on the same strand of DNA. 2. True or false: Cells can replicate and transcribe DNA that contains thymine dimers. 3. Photolyase is an enzyme that cells use to repair thymine dimers in a ______-dependent manner. 4. Excision repair, which is also used to correct thymine dimers, requires 5. What enzyme(s) is/ are involved in replacing the removed nucleotides following excision repair?
-covalent -false -light -none of these -DNA polymerase, followed by DNA ligase
Match the listed objects and compounds with the appropriate method used to destroy microbes and viruses on/in them: Moist heat Dry heat Radiation
-culture media and milk -medical waste, inoculating loop, medical carcasses -meat products and heat sensitive medications
Which of the following kills food microbes, rather than just reducing their growth?
-irradiation
Select the statements about ionizing radiation that are true.
-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
Categorize the given chemicals according to their uses. Wounds Medical instruments Soaps
-metals, halogens -aldehydes, ethylene oxide, peroxygens -biguanides, phenolics
Categorize the given medical instruments: critical semi critical non critical
-scalpel, needles, venous catheter -gastrointestinal endoscope, endotracheal tube, thermometer -stethoscope, blood pressure cuff
Germicides known as ____________ can destroy all microbes including both bacterial endospores and all types of viruses. ____________ disinfectants destroy all viruses and vegetative cells but will not kill endospores. ____________ 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. Germicides known as ____________ disinfectants kill vegetative cells except for mycobacteria and are unable to destroy nonenveloped viruses and endospores.
-sterilants -high level -intermediate level -low level
1. In the cases presented, what was the most probable route of transmission of the pathogen? 2. Although the epidemiological data collected from interviews implicated contaminated recreational water as the source of the outbreaks, negative results from the recreational water samples were obtained in most cases. Please explain this apparent contradiction. 3. Evaluate the effectiveness of the hyperchlorination of recreational waters at the facilities in these cases. 4. Discuss the role of public education in reducing the transmission of Cryptosporidium and other pathogenic microbes at recreational water venues. 5. Knowing that public water supplies to towns and cities are well purified by various means, do Cryptosporidium outbreaks still occur? Explain. 6. Conduct additional research and discuss other recreational water activities that pose a risk for microbial infection. What genera of organisms most commonly cause these types of infections?
-the pathogen remained in the water despite filtration and chlorine. So this recycled water included the protozoan and was exposed to all visitors who came in contact with the water -I assume that since the pathogen is so small and that since the park is 11,000-square-foot that the protozoan was so distributed that it was not enough to represent a positive result -Hyperchlorination will be ineffective for removing Cryptosporidium specifically because Cryptosporidium is resistant to Chlorine -Proper purification is obviously important to reduce the amount of pathogens in recycled water. However pathogens come in many different forms and are resistant to different things methods of purification. This is why it is important to consider and perform many different methods to remove these different types of pathogens -It is still possible for Cryptosporidium to occur if one were to come in contact with contaminated water that was not purified. Examples include drinking river water while camping or being exposed at a public pool because people are constantly entering and contaminating the water -Certain water sports can also be increase a risk for microbial infections. In addition, children are also more likely at risk considering they are more likely to both contaminate water by producing feces into the water and are more likely to accidently swallow more water. Bacteria, viruses, and protozoans can all contribute to water borne microbial infections but I think bacteria is most common.
Select the reasons sugar or salt can be used for food preservation. Check all that apply.
-they may cause plasmolysis -they dehydrate the bacterial cells -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 but bleach must be diluted because high concentrations are toxic and corrosive. To obtain an effective concentration of chlorine when using household bleach, a 1:100 dilution is made. This means that ______ mL of bleach is added to ______ mL of water
1.0; 99
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
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 min
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
How many agar plates do you have to analyze at the end of your experiment?
90
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.
How could this type of scenario be avoided in the future?
All equipment/ supply carts in healthcare facilities should be disinfected between procedures
Chemical germicides
All of the answer 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 temperature of use.
Review the chart*. How many total bacteria are on the hands of the people who wash their hands with water only, assuming that each colony arises from a single cell?
Approximately 450
Which of the following concerns would lead a user to wash an item after it had been treated with a germicide?
Corrosive residue left after treatment.
Please select the INCORRECTLY matched pair
D-value - time to destroy 10% of microbes present (correct: Critical instrument - scalpels and needles. Bacterial endospores - highly resistant. Sterilants - destroy all microbes including endospores and viruses. Incineration - burns cells to ashes)
Choose which of the following best describe the difference between a disinfectant and an antiseptic.
Disinfectants are antimicrobial chemicals used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. Antiseptics are antimicrobial chemicals that can be used on skin or tissues to achieve the same result
Which are essentially equivalent treatments?
Dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes
Which of the following are resistant to destruction by typical disinfection methods?
Endospores of Bacillus and Clostridium
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
Which of the following statements is FALSE regarding Giardia?
It has a peptidoglycan cell wall
Which is true of iodine?
It is usually found as tinctures or iodophors
Identify the difference between the use of depth filters and membrane filters in sterilizing fluids.
Membrane filters have smaller pores than depth filters, but depth filters have complex passages that retain microbes while letting the fluid through. Both methods are efficient.
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
Assuming strict adherence to recommended protocols, which of the following achieves sterilization?
Steam autoclaving
Rank the germicides from most to least potent
Sterilants High-level disinfectants Intermediate-level disinfectants Low-level disinfectants
Which is true of nosocomial infections?
They are acquired by susceptible people in the hospital
T/F: Boiling is very effective at removing most common waterborne pathogens.
True
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.
Which of the following destroys acellular infectious agents?
Virucides
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 is (are) considered when selecting a germicidal chemical?
all (Toxicity AND cost, Cost AND compatibility with the material being treated, Compatibility with the material being treated AND environmental impact, Environmental impact, toxicity AND cost)
A sterile item is free of
all viable microbes, endospores, AND viruses
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
To reduce or eliminate disease-/spoilage-causing organisms, food is often subjected to
cold, heat, radiation, chemical additives -all of the above
Phenolics
denature proteins and destroy cytoplasmic membranes
Moist heat primarily destroys microbes by
denaturing their proteins
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
Chlorine has traditionally been used to disinfect water, preventing the spread of waterborne illnesses. However, chlorine (and other disinfectants) can react with naturally occurring water chemicals, forming ______, which can have long-term health risks.
disinfection by-products (DBP's)
Generally, membrane filters are not used to remove
enzymes from liquids
T/F: 100% ethanol is twice as effective as 60% ethanol at controlling bacteria
false
T/F: Cold and freezing are very effective in killing bacteria
false
T/F: Dry heat takes a much shorter time to sterilize material than wet heat.
false
T/F: Handwashing with regular soap removes all normal microbiota from the skin.
false
T/F: Heat treatment is an effective method for sterilization or disinfection of all materials
false
T/F: Hydrogen peroxide may be used as a sterilant on living tissue
false
T/F: Measures to prevent prion contamination of healthcare settings have been in place for the past several decades and fully control the risk.
false
T/F: Microwaves kill microorganisms directly
false
T/F: Pasteurization results in the sterilization of food products
false
T/F: Prions are easily destroyed by common sterilization procedures
false
T/F: Sterilization is the destruction of all living microbes from a surface by physical or chemical means
false
T/F: The endospores of Pseudomonas make that organism very difficult to kill
false
Review the chart*. Which bar(s) represent(s) the control in this experiment?
green
Which of the following can be used to make drinking water safe? Check all that apply.
halogens ozone
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.
From reading this case, you know that
hepatitis C is caused by a virus
Oxidation of proteins is achieved most readily
in a hot air oven
The most important function of nitrites in processed foods is to
inhibit the germination of Clostridium botulinum endospores
Moist heat kills microorganisms by
irreversible denaturation of proteins
Chlorhexidine
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
Glutaraldehyde
is very good for use on heat-sensitive medical items
Ethylene oxide is gas that
is very useful for sterilizing heat- or moisture-sensitive items
Hand washing with plain soap is very effective in controlling spread of microorganisms because
it is very effective at the mechanical removal of microorganisms
Boiling is not a reliable method for sterilization because
its does not destroy heat resistant endospores
What part of the body is affected with hepatitis?
liver
Liquid media containing heat-sensitive components would best be sterilized by
membrane filtration
Select the method that would be used to sterilize a liquid containing vitamin B12 and human growth hormone
membrane filtration
Alcohols are not reliably effective at destroying
non-enveloped viruses AND endospores
__________is a brief heat treatment that reduces the number of spoilage organisms and destroys pathogens. It can be used on foods or inanimate objects.
pasteurization
Silver sulfadiazine, a combination of silver and a sulfa drug, is used to
prevent infection of second- and third-degree burns
Chlorine
readily reacts with organics to produce potentially carcinogenic trihalomethanes
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
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
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
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
T/F: Generally, heavy metals, except silver, have been proven to be too toxic for use on human tissue and are no longer used medically
true
T/F: Organic acids, such as benzoic acid, are often added to foods to prevent microbial growth.
true
T/F: The government agencies that regulate germicidal chemicals are the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA).
true
T/F: The more bacteria one starts with, the longer it will take to kill them all
true
T/F: The more bacteria present on or in something, the longer it takes to kill them all.
true
T/F: Upon heat treatment, bacteria die at a constant proportion
true
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.
