Deck 11: Physical and Chemical Agents for Microbial Control

Question 1

Explain the purposes of microbial control and differentiate between physical, mechanical, and chemical methods.

Answer 1

Microbial control consists of decontamination procedures that effectively remove or kill the contaminants. These contaminants are known as microbes in microbiology. Microbes are contaminants that are undesirable in a given location or at a certain time. The methods of decontamination consist of physical, chemical and mechanical means of disinfection or sterilization.
Physical means of decontamination consist of heat and radiation that results in the sterilization of inanimate objects, such as what is accomplished through autoclaving materials. Sterilization is the complete removal of all viable microbes. Chemical means of microbial control include the use of gases and liquids to either sterilize or disinfect. Methods of mechanical removal consist of filtrating either the air or liquids in order to remove unwanted microbes.

Question 2

Summarize the major categories of microbial control and its purposes.

Answer 2

The methods used for controlling microbes are known as decontamination procedures that can destroy and remove contaminants. The contaminants are referred to be microorganisms that occur as undesirable or unwanted agents at given time and place. These agents must be removed to maintain the environment or substance to be safe.
The decontamination methods include using of physical, mechanical and chemical agents. The physical agents include heat or radiation. The heat is used in the form of dry or moist heat and radiation in the form of ionizing or non-ionizing. The microbial control methods are used to remove microorganisms causing infection or spoilage. These methods do not harm microorganisms present in environment or on the surface of human body. The targeted microbial population includes pathogens such as bacteria, fungi, Yeast and protozoans, worms, viruses and prions.
The microbial contaminants also include endospores of bacteria. Spores of fungi, cysts of protozoans and worms. All these microbial structures exhibit different degree of resistance and ability of contamination. For example; prions are proteinaceous infectious particles and bacterial endospores are formed by bacteria such as Bacillus and Clostridium exhibit high degree of resistance to various decontamination methods.
The chemical agents used include gases and liquids such as disinfectants and antiseptics. All these methods used to achieve sterilization or disinfection by removal or destruction of all viable microorganisms or pathogens and endospores from animate and inanimate objects and from surfaces.

Question 3

From chapter 2 , figure 2.20. Study this illustration of a cell membrane. In what ways could alcohol (Hint: a solvent) damage this membrane? How would that harm the cell?

Answer 3

No Answer

Question 4

Compare sterilization with disinfection and sanitization. Describe the relationship of the concepts of sepsis, asepsis, and antisepsis.

Question 5

Evaluate the relative resistance of different groups of infectious agents.

Question 6

Explain this graph that charts the reactions of a mesophilic bacterium to temperature. Blue shows the survival curve and brown the growth curve.

Question 7

Contrast various microbes and rate their variations in resistance to control agents.

Question 8

Define and differentiate among the major terms for microbial control, citing examples of each.

Question 9

Explain how the types and numbers of microorganisms can influence the effectiveness of control agents.

Question 10

Characterize the parameters of microbial death, and describe several factors that influence the rate of death.

Question 11

How is microbial death defined?

Question 12

Summarize what practices in microbial control influence the effectiveness of an antimicrobial agent.

Question 13

Why does a population of microbes not die instantaneously when exposed to an antimicrobial agent?

Question 14

Identify the targets of antimicrobial control agents, and explain what effects their modes of actions have.

Question 15

Distinguish between microbicidal and microbistatic effects on microbes, and tell why it is important to understand the difference.

Question 16

List the major types of physical agents used in controlling microbes.

Question 17

Why are antimicrobial processes inhibited in the presence of extraneous organic matter?

Question 18

Describe the basic effects of temperature on microbes.

Question 19

Describe four modes of action of antimicrobial agents, and provide examples of how they work.

Question 20

Define moist and dry heat, and explain their modes of action and relative effectiveness.

Question 21

What happens to microbes that encounter temperatures below their minimum and above their maximum growth temperatures?

Question 22

Differentiate between thermal death point and thermal death time, and provide examples of their uses.

Question 23

Summarize the nature, mode of action, and effectiveness of moist and dry heat on spores and vegetative cells.

Question 24

Describe several moist heat methods and their chief applications for sterilization and disinfection.

Question 25

Explain the concepts of TDT and TDP, using examples.

Question 26

Describe some methods using dry heat and its chief applications.

Question 27

What are the minimum TDTs for vegetative cells and endospores?

Question 28

Explain how cold temperatures and desiccation are used in microbial control.

Question 29

How can the temperature of steam be raised above 100°C? Which instrument is based on this technique and how is it used?

Question 30

Define radiation and assess the use of irradiation as a method of microbial control.

Question 31

What are the primary purposes of pasteurization, and what is ultrapasteurization?

Question 32

Differentiate between ionizing and nonionizing radiation in their modes of action.

Question 33

What are several microbial targets of pasteurization?

Question 34

Summarize the primary uses of ionizing and nonionizing radiation in sterilization and disinfection.

Question 35

Explain why desiccation and cold are not reliable methods of disinfection but how they can still be effective in microbial control.

Question 36

Describe the concept behind sterilization by filtration, including examples of applications.

Question 37

Define radiation and irradiation.

Question 38

Define the terms that are used to describe different methods of chemical control of microbes.

Question 39

Differentiate between the modes of action of ionizing radiation and ultraviolet radiation.

Question 40

Explain the desirable features of antimicrobial chemicals and what factors influence their effectiveness.

Question 41

What are some advantages and disadvantages of ionizing radiation as a method of control?

Question 42

Describe the types of halogens, their modes of action, and their clinical and commercial applications.

Question 43

Describe some applications of ionizing and ultraviolet radiation.

Question 44

Identify the characteristics of phenolic compounds and alcohols, explain how they act, and evaluate their primary uses.

Question 45

What are the advantages and disadvantages of using filtration as a method of control?

Question 46

Describe the characteristics of oxidizing agents and aldehydes, and summarize their main applications.

Question 47

Describe situations that require high-level disinfection and those for which medium- or low-level disinfection is adequate.

Question 48

Differentiate among the sterilizing gases and aerosols, and describe how they are used.

Question 49

What is the difference between a tincture and an aqueous solution?

Question 50

Explain how detergents, soaps, and heavy metals can be employed in clinical, commercial, and household microbial control.

Question 51

Name one chemical for which the general rule that a higher concentration is more effective is not true.

Question 52

Define sterilant , and name the principal sporicidal chemical agents.

Question 53

Summarize the chief forms and uses of chlorine compounds.

Question 54

What are the superior characteristics of iodophors over free iodine solutions?

Question 55

What are the modes of action of alcohols and phenolics?

Question 56

Why is hydrogen peroxide solution so effective against anaerobes?

Question 57

Give the uses and disadvantages of the heavy metal chemical agents, glutaraldehyde, and the sterilizing gases.

Question 58

What does it mean to say that a chemical has an oligodynamic action, and which compounds have this effect?

Question 59

An Introduction to Concept Mapping found at http:\\www.mhhe.com\talaro9 provides guidance for working with concept maps.
Construct your own concept map using the following words as the concepts. Supply the linking words between each pair of concepts.

Question 60

How would one best describe the state of being a carrier of HCV?
a. It is on the skin and transmitted through direct contact.
b. The person shows symptoms and is jaundiced.
c. The person has a chronic infection of the liver and harbours the virus.
d. The person has had contact with blood in a medical setting.

Question 61

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles, and in most cases, they do not have a single correct answer.
For each item on the following list, give a reasonable method of sterilization. You cannot use the same method more than three times for the whole list. The method must sterilize, not just disinfect; and the method must not destroy the item or render it useless unless there is no other choice. After considering a workable method, think of a method that would not work. Note: Where an object containing something is given, you must sterilize everything (for example, both the jar and the petroleum jelly [Vaseline] in it). Some examples of methods are autoclave, ethylene oxide gas, dry oven, and ionizing radiation.

Question 62

Select the correct answer from the answers provided. For questions with blanks, choose the combination of answers that most accurately completes the statement. A microbicidal agent has what effect?

A) sterilizes
B) inhibits microorganisms
C) is toxic to human cells
D) destroys microorganisms

Question 63

Compose a one- or two-paragraph answer that includes the factual information needed to completely address the question. Check Your Progress questions can also be used for writing-challenge exercises.
What is wrong with this statement: "Prior to vaccination, the patient's skin was sterilized with alcohol''? What would be the more correct wording?

Question 64

The main issue in the case of clinic-acquired HCV infections was:
a. use of unclean equipment
b. a high number of carriers
c. contamination of drugs
d. health workers who were IV drug abusers

Question 65

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles, and in most cases, they do not have a single correct answer.
Using pasteurization techniques as a model, compare the TDTs and explain the relationships between temperature and length of exposure.

Question 66

Select the correct answer from the answers provided. For questions with blanks, choose the combination of answers that most accurately completes the statement. Microbial control methods that kill ________ are able to sterilize.

A) viruses
B) the tubercle bacillus
C) endospores
D) cysts

Question 67

Compose a one- or two-paragraph answer that includes the factual information needed to completely address the question. Check Your Progress questions can also be used for writing-challenge exercises.
Would it be proper to say that a patient has been disinfected? Why or why not?

Question 68

Outline the chain of events involved in the transmission of HCV from an infected patient to several other patients through the actions of a medical worker.

Question 69

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles, and in most cases, they do not have a single correct answer.
It may seem contradictory that lyophilization can be used to preserve foods yet also be used to keep cultures of microbes viable. Explain how these applications can be reconciled.

Question 70

Select the correct answer from the answers provided. For questions with blanks, choose the combination of answers that most accurately completes the statement. Any process that destroys the non-spore-forming contaminants on inanimate objects is

A) antisepsis
B) disinfection
C) sterilization
D) degermation

Question 71

Compose a one- or two-paragraph answer that includes the factual information needed to completely address the question. Check Your Progress questions can also be used for writing-challenge exercises.
Think of three situations in which the same microbe would be considered a serious contaminant in one case and completely harmless in another.

Question 72

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles, and in most cases, they do not have a single correct answer.
A supermarket\drugstore assignment: Look at the labels of 10 different products used to control microbes, and make a list of their active ingredients, their suggested uses, and information on toxicity and precautions.

Question 73

Select the correct answer from the answers provided. For questions with blanks, choose the combination of answers that most accurately completes the statement. Sanitization is a process by which

A) the microbial load on objects is reduced
B) objects are made sterile with chemicals
C) utensils are scrubbed
D) skin is debrided

Question 74

Compose a one- or two-paragraph answer that includes the factual information needed to completely address the question. Check Your Progress questions can also be used for writing-challenge exercises.
Explain what features of endospores make them so resistant to microbial control, and how sterilizing techniques work to destroy them.

Question 75

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles, and in most cases, they do not have a single correct answer.
Devise an experiment that will differentiate between bactericidal and bacteriostatic effects.

Question 76

Select the correct answer from the answers provided. For questions with blanks, choose the combination of answers that most accurately completes the statement. An example of an agent that lowers the surface tension of cells is

A) phenol
B) chlorine
C) alcohol
D) formalin

Question 77

Compose a one- or two-paragraph answer that includes the factual information needed to completely address the question. Check Your Progress questions can also be used for writing-challenge exercises.
Explain some of the problems involved in sterilizing delicate and heat-sensitive instruments such as endoscopes, syringes, needles, catheters, and other instruments.

Question 78

Critical thinking is the ability to reason and solve problems using facts and concepts. These questions can be approached from a number of angles, and in most cases, they do not have a single correct answer.
There is quite a bit of concern that chlorine used as a water purification chemical presents serious dangers. What alternative methods covered by this chapter could be used to purify water supplies and keep them safe from contamination?

Question 79

Select the correct answer from the answers provided. For questions with blanks, choose the combination of answers that most accurately completes the statement. High temperatures ________ and low temperatures ________.

A) sterilize, disinfect
B) kill cells, inhibit cell growth
C) denature proteins, burst cells
D) speed up metabolism, slow down metabolism

Question 80

Compose a one- or two-paragraph answer that includes the factual information needed to completely address the question. Check Your Progress questions can also be used for writing-challenge exercises.
The shelf life and keeping qualities of fruit and other perishable foods are greatly enhanced through irradiation, saving industry and consumers billions of dollars. How would you personally feel about eating irradiated fruit? How about spices that had been sterilized with ETO?