Bio 150: microbiology: Chapter 11:
Glutaraldehyde
Sporicidal High level of activity Can irritate skin; toxic if absorbed Not inactivated by organic matter; unstable
Hydrogen peroxide, stabilized
Sporicidal High level of activity Toxic to eyes; toxic if ingested Improved stability; works well in organic matter
Ethylene oxide gas
Sporicidal High level of activity Very dangerous to eyes, lungs; carcinogenic Explosive in pure state; good penetration; materials must be aerated
Chlorine
Sporicidal (slowly) Intermediate level of activity Gas is highly toxic; solution irritates skin Inactivated by organics; unstable in sunlight Chemical
______ is the most common physical agent used to control microbes
heat
Osmotic Pressure
Adding large amounts of salt or sugar to foods creates a hypertonic environment •Causes plasmolysis in bacteria •Makes it impossible for microbes to multiply •"Cured" meats are treated with high salt concentrations so they can be kept for long periods without refrigeration •High sugar in jams and jellies has the same effect
Tinctures:
Antimicrobial chemicals dissolved in pure alcohol or water-alcohol mixtures
T/F: iodine compounds are commonly used for household cleaning
F
Chlorhexidine
Most bacteria, some viruses, fungi Low to intermediate level of activity Low toxicity Fast-acting, mild, has residual effects Chemical
Alcohols
Most bacteria, viruses, fungi Intermediate level of activity Toxic if ingested; a mild irritant; dries skin Flammable, fast-acting Chemical
Aqueous solution:
Solutions containing pure water as the solvent
Phenolics
Some bacteria, viruses, fungi Low to intermediate level of activity Can be absorbed by skin; can cause CNS damage Poor solubility; expensive Chemical
Complete the sentences to test your knowledge of factors affecting microbial death rate.
The effectiveness of a particular microbicidal agent is governed by several factors besides time. The number of microbes affects the action of an agent, as does the composition of the population. The temperature as well as the pH level of the environment will also influence the action of microbicidal agents. The concentration of the agent as well as its mode of actionagainst microbes also play a role in its ability inactivate microbes. Finally, the presence of organic matter, such as saliva and blood, also inhibits the action of many microbicidal agents.
boiling water
This exposes a material to a temperature of 100°C. Thirty minutes of exposure will disinfect but will not sterilize.
What represents a nonionizing form of radiation, often used for disinfection purposes? Cathode rays X rays Gamma rays UV radiation
UV radiation
Is ionizing radiation sterilization?
Yes
Select the advantages of phenolic compounds as antimicrobial agents. Check all that apply. Remain effective in the presence of organic matter Generally nontoxic Strongly microbicidal Effective against prions
a c
Select the physical methods of microbial control. Check all that apply. Steam autoclave Incineration Pasteurization Desiccation Boiling water
a c e
Describe the difference between bactericidal and bacteristatic agents.
bactericidal kills bacteria (except those in the endospore stage), bacteristatic only prevents bacteria from multiplying but not kill them
Sterilization is achieved by flash pasteurization. hot water. boiling water. steam autoclave. All of the choices are correct.
d
T/F: Surgeons preparing for an invasive surgical procedure will scrub their hands thoroughly, and then they use a strong alcohol-based hand sanitizer which renders their hands sterile.
false
If an agent disrupts the cell wall, the cell is likely to experience death by:
lysis
Ultraviolet radiation produces ________ dimers.
pyrimidine
thermal death time
shortest length of time required to kill all test microbes at a specified temperature
cold is ______
sterilizing
The lowest temperature required to kill all of the microbes in a sample in 10 minutes is the ______ _____ _____
thermal death point
Critical medical devices:
•Expected to come into contact with sterile tissues
Semicritical medical devices:
•Come into contact with mucosal membranes
Put the following in order from most resistant to least resistant: Protozoa, bacterial endospores, enveloped viruses, nonenveloped viruses, protozoan cysts
Bacterial endospores, protozoan cysts, protozoa, nonenveloped viruses, enveloped viruses
Silver nitrate
Bactericidal Low level of activity Toxic, irritating Discolors skin
Select the appropriate uses of hydrogen peroxide for antimicrobial purposes. Check all that apply. Contact lens disinfection Large-scale drinking water disinfection Sterilization of laboratory glassware Low-temperature sterilizing cabinets for colonoscopes Wound cleansing
a d e
Select the appropriate uses of hydrogen peroxide for antimicrobial purposes. Check all that apply. Contact lens disinfection Large-scale drinking water disinfection Sterilization of laboratory glassware Low-temperature sterilizing cabinets for colonoscopes Wound cleansing Disinfection of countertops and other environmental surfaces
a d e
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. alcohols
a 70% solution is best for denaturing microbial proteins
What is the best measurement to consider when dealing with heat-sensitive materials? Thermal death point Thermal death time
b
Select all of the statements that accurately reflect the process of filtration. Filtration can be effectively used to remove microbial contaminants from solid materials. Filters, charcoal, and diatomaceous earth can all be used to remove microbial contaminants in the process of filtration. Filters with pores of the smallest diameter are utilized to sterilize air and liquid samples. Filtration is beneficial in the preparation of products, such as serum, that cannot withstand high heat. Filtration can effectively remove even soluble toxins in a pharmaceutical grade drug preparation.
b c d
Select all of the statements that accurately reflect the use of alcohols in microbial control. Methyl alcohol is commonly used due to its potent antimicrobial effects. Higher concentrations of alchohol in antimicrobial solutions often do not make them more effective. Alcohol does not destroy bacterial endospores at room temperature. Alcohol is more effective against enveloped viruses versus nonenveloped viruses. Most hand sanitizers contain methyl alcohol.
b c d
Select the characteristics of a chemical control agent that make it a desirable agent. Check all that apply. Corrosive to metals and plastics Water or alcohol soluble and stable "-cidal" to a wide range of microbes, but nontoxic to humans and animal tissue Rapidly effective in low concentrations Ineffective in the presence of organic matter Inexpensive Short-lived, spontaneously inactivates with time
b c d f
Dry heat:
•Air with a low moisture content that has been heated by a flame or electric heating coil •Temperature ranges from 160°C to several thousand degrees Celsius •Lack of water increases stability of some protein configurations, necessitating higher temperatures •At high temperatures, dry heat oxidizes cells, burning them to ashes
antisepsis (degermation)
Destruction of most microbial life on living tissue Application of chemical agents (antiseptics) to exposed body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens •Reduction of the number of microbes on the skin •Involves scrubbing the skin or immersing it in chemicals, or both •Emulsifies oils on the outer cutaneous layer •Mechanically removes potential pathogens on the outer layers of the skin
hypochlorites
Disinfection in dairies, food processing plants, restaurants, hospitals, and homes
Move the types of physical control to their correct category.
Dry Heat: incineration hot-air oven Moist Heat: boiling water pasteurization non-pressurized steam steam under pressure Dessication: dehydration by exposure to normal room air Radiation: gamma and x-rays UV rays
pasteurization
Heat is applied to beverages to prevent spoilage and kill pathogens, but it does not sterilize. Protocols include holding liquids at 71.6°C for 15 sec. or at 63°C for 30 minutes.
pure silver ions
Incorporated into urinary catheters
chlorine gas
Large scale disinfection of drinking water
iodophors
Skin and tissue antisepsis
Dyes are important for:
Staining techniques, selective and differential media, chemotherapeutic drugs
T/F: A chemical labeled as bactericidal will kill bacteria whereas a chemical labeled as bacteriostatic will inhibit bacterialgrowth but will not kill them.
T
T/F: UV radiation is most lethal from 240 nm to 280 nm
T
T/F: an agent's effect on cells is known as its mode of action
T
T/F: silver and mercury are still used in germicidal preparation
T
Steam under pressure
This method requires the use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes.
Match the term to its description to test your understanding of the use of moist heat methods to control microbial growth.
This method requires the use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes.-steam under pressure Heat is applied to beverages to prevent spoilage and kill pathogens, but it does not sterilize. Protocols include holding liquids at 71.6°C for 15 sec. or at 63°C for 30 minutes.-pasteurization This exposes a material to a temperature of 100°C. Thirty minutes of exposure will disinfect but will not sterilize.-boiling water
silver nitrate
Topical germicide on mouth ulcers and root canals
silver sulfadiazine
Used in an ointment on 2nd and 3rd degree burns
Choose the method used to sterilize an inoculation loop used in lab for culturing bacteria. Incineration Radiation Pasteurization Hot air Autoclaving
a
Please select two methods that can be used for long-term preservation of microbial cultures. Irradiation Deep freezing (-70oC to -135oC) Filtration Pasteurization Lyophilization
b e
What chemical agents would be ineffective against this organism? Hydrogen peroxide Phenolic compound Glutaraldehyde Ethylene oxide gas Alcohols at room temperature
b e
Alcohol acts as a surfactant and a protein coagulant. Which of the following statements are true concerning its mechanism of action? 100% ethanol is a better microbicide than lower concentrations since the more concentrated it is, the more effective the activity. Ethanol is a better microbicide than isopropyl alcohol. 70% ethanol is a better microbicide than 100% alcohol since water molecules are necessary to coagulate proteins. Despite not killing endospores, ethanol is still considered a sterilizing agent.
c
Select the phrase that describes the antimicrobial activity of alcohols. Disrupt peptidoglycan structure Destruction of endospores Disrupt membrane lipids and denature proteins Interfere with nucleic acid replication and transcription
c
The cell can no longer regulate the passage of materials in and out of the cell. Which of the four main targets is affected in this scenario? Cellular synthesis Proteins Cell membrane Cell wall
cell membrane
the shortest length of time required to kill all tests microbes at a specified temperature is referred to as thermal _______ __________
death time
filtration has been used in which of the following:
decontamination of milk products water purification decontamination of air sterilization of medical products
Scrubbing or immersing the skin in chemicals to reduce the numbers of microbes on the skin is ______.
degermation
A(n) ______ agent would be used to destroy bacteria on a countertop whereas a(n) _______ agent would be used on skin prior to making an incision.
disinfectant; antiseptic
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. detergents
disrupt cell membranes, but only rated for low-level disinfection
Select the microorganism that is least resistant to chemical and physical control measures. Gram-negative bacteria Non-enveloped (naked) viruses Protozoan cysts Enveloped viruses Gram-positive bacteria
enveloped viruses
T/F: Mercury is a heavy metal that today is increasingly incorporated into plastic, steel, and textiles to create antimicrobial surfaces and clothing.
f
T/F: Desiccation is a form of physical control of microorganisms that can be used in moist or dry forms.
f
T/F: Nonionizing radiation exhibits good penetrating power and can be used for cold sterilization.
f
Because prions are so resistant to typical control methods, it is not important to consider them when attempting to sterilize a substance or environment. True False
false
T/F: Nonionizing radiation exhibits good penetrating power and can be used for cold sterilization.
false
The two microbial forms most resistant to chemical and physical control measures are _______ or proteinaceous infectious particles, and ______ produced by Bacillus and Clostridium species.
prions; endospores
The native state of certain enzymes are destroyed by heat, and the active sites are no longer able to bind with substrate. Which of the four main targets is affected in this scenario? Cell wall Proteins Cellular synthesis Cell membrane
proteins
boiling water can be an effective means of ______ in the clinic and home
sanitization disinfection
antimicrobial solutions with alcohol or water-alcohol mixtures as the solvent are called
tinctures
Select the most disadvantageous characteristic of phenolics. Difficult to use Limited in their antimicrobial spectrum Inactivated by organic matter Toxicity
toxicity
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. phenolics
triclosican is a member of this antimicrobial category
Clostridium difficile forms endospores. This characteristic makes this pathogen a concern for healthcare-associated infections. True False
true
T/F: Salting of meat prior to the development of refrigeration technology was an example of using osmotic pressure to control microbial spoilage of this food product.
true
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. chlorhexidine
used in hand scrubs, prepping skin for surgery
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. ethelyne oxide
used to disinfect delicate instruments and plastic materials
Review the characteristics of chemical agents of microbial control by completing each sentence.
Antimicrobial chemicals occur in liquid, gaseous, or even solid forms. They range from disinfectants and antiseptics to sterilants and preservatives, which are chemicals which can be used to inhibit the deterioration of food products. The use of chemical agents as germicides is very important in health-related fields today, due to their ability to have rapid action in low concentrations and their ability to remain functional when solubolized in water or alcohol. In addition, many of these agents have broad-spectrum microbicidal action without exhibiting toxicity as well as the ability to sustain a persistent action on inanimate surfaces. Other agents are resistant to the inactivating action of organic matter, while others exhibit noncorrosive, sanitizing, or deodorizing properties. Many are affordable and readily available to users.
The word thermal indicates the use of heat. In general, _____ temperatures require _____ exposure times. higher; shorter higher; longer
a
What represents a nonionizing form of radiation, often used for disinfection purposes? Cathode rays Gamma rays UV radiation X rays
c
disinfection
Destruction of most microbial life on inanimate surfaces The use of a physical process or a chemical agent (disinfectant) to destroy vegetative pathogens but not bacterial endospores •Disinfectants are normally only used on inanimate objects
Which of the following represents one of the four major targets of antimicrobial agents? Multiple Choice Lysosomes Flagella Cell wall Capsules
cell wall
Thymine dimers are formed in DNA, preventing replication. Which of the four main targets is affected in this scenario? Cellular synthesis Cell membrane Cell wall Proteins
cellular synthesis
Cellular targets of physical and chemical agents:
1. The cell wall Damage to the cell wall: •Blocking cell wall synthesis •Digesting the cell wall •Breaking down the surface of the cell wall A cell with a damaged cell wall is fragile and becomes lysed easily Detergents and alcohols disrupt the cell wall 2. The cell or cytoplasmic membrane Disruption of the cell membrane causes: •Loss of selective permeability •Loss of vital molecules •Allows the entry of damaging chemicals 3. Cellular synthetic processes (DNA, RNA) 4. Proteins Microbial cells depend on an orderly and continuous supply of proteins •Substances that inhibit ribosomes will also inhibit protein synthesis Nucleic acids are necessary for the continued functioning of microbes •Agent that impedes the transcription of DNA replication or DNA transcription or changes the genetic code is antimicrobial
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. Hydrogen Peroxide
3% solution is used as an antiseptic for skin and would cleansing
Review various thermal death measurements by completing each sentence.
Adequate sterilization requires that both temperature and length of exposure be properly controlled. In general, higher temperatures allow shorter exposure times, while lowertemperatures require longer exposure times. In terms of these strategies, the thermal death time is defined as the shortest length of time required to kill all test microbes at a specified temperature. An optional measurement used to compare the susceptibility of microbes to heat is the thermal death point, which is defined as the lowest temperature required to kill all microbes in a sample in 10 minutes.
Review the cellular targets of physical and chemical antimicrobial agents by completing each sentence.
An antimicrobial agent's adverse effect on cells is known as its mode of action. Such antimicrobials exhibit a range of cellular targets, the least selective being the most effective against the widest range of microbes and the most selective agents exhibiting specificity in terms of cellular targets and microbial types they are effective against. Potential cellular targets of various physical and chemical forms of antimicrobials include the cell wall, whose synthesis can be blocked by these agents or whose structure can be altered as well. Another potential target is the cell membrane, whose surface tension can be reduced by various microbicidal agents resulting in a loss of selective permeability in the cell. Physical and chemical agents can also interfere with protein synthesis through disruption of ribosome activity, protein function through the denaturation of a protein's native state, and finally disrupting the synthesis or structure of nucleic acids.
Soaps
Certain very sensitive species Very low level of activity Nontoxic; few if any toxic effects Used for removing soil, oils, debris, and reducing load
sterilization
Destruction of all microbial life A process that destroys or removes all viable microorganisms, including viruses •Any material that has been subjected to this process is said to be sterile Sterilized products are essential to human well- being: •Surgical instruments •Syringes •Commercially packaged foods
decontamination (sanitization)
Mechanical removal of most microbes from living or inanimate surfaces •Any cleansing technique that mechanically removes microbes and debris •Reduces contamination to safe levels •Sanitizer: a soap or detergent used to sanitize •Living and non-living objects are treated
Quaternary ammonium compounds (quats)
Some bactericidal, virucidal, fungicidal activity Low level of activity Irritating to mucous membranes; poisonous if taken internally Weak solutions can support microbial growth; easily inactivated
Because of its ability to decompose into oxygen and water, hydrogen peroxide is very useful against what group of organisms? Protozoans Anaerobic bacteria Fungi Viruses
b
Is non-ionizing radiation sterilization? How about disinfecting?
Yes for surfaces, No for depths Yes, it does not penetrate
A chemiclave is a piece of equipment that uses what antimicrobial agent for the purpose of sterilization? Ethylene oxide Hydrochloric acid Carbon dioxide Silver nitrate
a
Choose the aldehyde that is the most toxic, limiting its clinical usefulness. Formaldehyde/formalin Ortho-phthalaldehyde (OPA) Glutaraldehde Ethylene oxide Hydrogen peroxide
a
Order these types of microbes in terms of their resistance, from least resistance to most resistance. Enveloped viruses, naked viruses, vegetative bacteria, protozoans, endospores, prions Naked viruses, enveloped viruses, vegetative bacteria, protozoans, endospores, prions Enveloped viruses, naked viruses, protozoans, vegetative bacteria, endospores, prions Enveloped viruses, naked viruses, protozoans, prions, vegetative bacteria, endospores
a
The two microbial forms most resistant to chemical and physical control measures are _______ or proteinaceous infectious particles, and ______ produced by Bacillus and Clostridium species. prions; endospores porins; granzymes ribozymes; capsules micro RNAs; envelopes
a
Select the applications of ethylene oxide sterilization. Check all that apply. Dried food and spices Plastics Prepackaged medical devices Bacterial growth media Milk and dairy products
a b c
The factors that must be considered when attempting to use heat for sterilization include which two of the following? Time Concentration Population Temperature
a b d
Evaluate the statements below, and select those that correctly apply to the use of radiation as a microbial control mechanism. The use of radiation to control microbial growth comes in two forms; ionizing and nonionizing radiation. Of the two, ionizing radiation is the most destructive. Nonionizing radiation involves electrons being bombarded with enough energy to eject them from their atoms. Gamma rays are an example of this. Nonionizing radiation, e.g., UV light, causes electrons to make a quantum leap to an orbital with a higher energy state, which causes thymine dimers to form, but does not create ions. Ionizing radiation involves electrons being bombarded with enough energy to eject them from their atoms. X rays are an example of this. The use of radiation to control microbial growth comes in two forms; ionizing and nonionizing radiation. Of the two, nonionizing radiation is the most destructive.
a c d
Select the methods that illustrate the use of moist heat to control microbes. Check all that apply. Steam autoclave Incineration Pasteurization Desiccation Boiling water
a c e
Select all of the food items where microbial growth is controlled by means of osmotic pressure. Honey Apple cider Salt-cured meats Milk Yogurt Jellies
a c f
Choose the microbial control method that neither inhibits nor kills microbes, but instead physically removes them from liquids or air. Lyophilization Filtration Irradiation Desiccation Cold sterilization
b
a sterile object is free of:
all viable microorganisms and viruses
A chemiclave is a piece of equipment that uses what antimicrobial agent for the purpose of sterilization? Carbon dioxide Ethylene oxide Hydrochloric acid Silver nitrate
b
Choose the statement that identifies the major disadvantage of both cold and desiccation in terms of microbial control. These methods are technically difficult and labor-intensive. These methods may encourage growth of microbial populations. These methods are bacteriostatic rather than bactericidal. These methods produce harmful by-products and are costly.
c
Is it likely that the increase in antibiotic-resistant organisms is related to the increase in hand washing in healthcare facilities? Yes, because the microbiota embedded in the skin oils of the healthcare workers are being killed off and replaced by resistant organisms. Yes, because the organisms are developing resistance to the alcohol and therefore antibiotics also. No, because the increase in antibiotic-resistant organisms is a result of exposure to antibiotics, not alcohol. No, because the handwashing prevents organisms from becoming antibiotic-resistant.
c
Select the statement that best describes the antimicrobial activity of chlorhexidine. Chlorhexidine interferes with nucleic acid replication and transcription. Chlorhexidine disrupts peptidoglycan structure. Chlorhexidine targets cell membrane components and denatures proteins. Chlorhexidine causes the destruction of endospores.
c
Triclosan is a phenolic compound present in some hand sanitizers that targets a specific protein mediating fatty acid synthesis. Are microbes more or less likely to develop resistance to triclosan than to alcohol? Less likely, since the cell membrane structure can be altered genetically to resist the surfactant properties of alcohol, whereas triclosan kills the cell outright. Less likely, since we use more alcohol overall than triclosan. More likely, since triclosan has a specific target which can be altered genetically, whereas alcohol's surfactant properties cannot be avoided. More likely, since we use more triclosan overall than alcohol.T
c
A drug destroys the peptidoglycan molecules of a bacterial cell. Which of the four main targets is affected in this scenario? Cell wall Cell membrane Proteins Cellular synthesis
cell wall
what are the following effects of iodinizing foods
changes in texture of some foods killing of bacterial pathogens small decreases in thiamine
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. Halogens
chlorine bleach iodine
match each medical device with its classification critical semicritical noncritical endoscopy tube artificial knee crutches
critical: artificial knee semicritical: endoscopy tube noncritical: crutches
Which of these represents a chemical sterilant? Chlorhexidine Phenolics Alcohols Ethylene oxide
d
If we can kill all microbes in a substance in five minutes at 150 °C, that is the best temperature to use for sterilization. True False
false
T/F: Moist heat methods operate at higher temperatures and longer exposure times as compared to dry heat methods.
false
Choose the microbial control method that neither inhibits nor kills microbes, but instead physically removes them from liquids or air. Desiccation Cold sterilization Filtration Irradiation Lyophilization
filtration
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. heavy metals
mercury and silver are examples
Cationic detergents are surface active agents, also known as ______, which damage bacteria by binding bacterial surface proteins and disrupting ______.
surfactants; cell membranes
T/F: Salting of meat prior to the development of refrigeration technology was an example of using osmotic pressure to control microbial spoilage of this food product.
t
The easiest microbial forms to kill or inhibit are ______.
vegetative bacteria and fungi
Move the chemicals or descriptions to their correct category to review general characteristics of germicidal agents. aldehydes
very toxic, but used to disinfect surgical instruments
Lyophilization:
•A combination of freezing and drying •Common method of preserving microbes and other cells in a viable state •Pure cultures are frozen instantaneously and exposed to a vacuum that removes water
Filtration:
•An effective method to remove microbes from air and liquids •Fluid is strained through a filter with openings large enough for liquid to pass through, but too small for microbes to pass through •Coarse: 8 microns •Ultrafine: 0.02 micron •Used in liquids that cannot withstand heat •Alternative method for decontaminating milk and beer •Important step in water purification •Efficient means of removing airborne contaminants
Radiation:
•Energy emitted from atomic activities and dispersed at high velocity through matter or space Radiation suitable for microbial control: •Gamma rays •X rays •Ultraviolet radiation
Moist heat:
•Hot water, boiling water, steam •Temperature ranges from 60°C to 135°C •Operates at lower temperatures and shorter exposure times than dry heat •Most microbicidal effect is coagulation and denaturation of proteins to permanently halt microbial metabolism
Factors Affecting the Microbicidal Activity of Chemicals
•Nature of microorganisms being treated •Nature of material being treated •Degree of contamination •Time of exposure •Strength and chemical action of the germicide
Factors That Affect Death Rate
•Number of microorganisms •Nature of the microbes in the population •Type of microbial growth •Temperature and pH of the environment •Concentration of the agent •Mode of action of the agent •Presence of solvents, interfering organic matter, and inhibitors
Noncritical medical devices:
•Those that do not touch the patient or are only expected to touch intact skin
Desiccation:
•dehydration of vegetative cells directly exposed to normal room air •Some delicate pathogens can be killed by desiccation •Some pathogens can be preserved upon desiccation •Desiccation can preserve foods because it reduces the amount of water available to support microbial growth
