Microbiology Ch. 9

Question 1

Discuss the historical roles played by Ignaz Semmelweis and Joseph Lister in preventing the spread of infection. (you will probably have to do a little Internet research to find out more information about these two men)

Answer 1

Ignaz Semmelweis:

Ignaz Semmelweis was the first doctor to discover the importance for medical professionals of hand washing. In the 19th century, it was common for women to die from an illness contracted during or after childbirth, known as childbed fever. While working at an obstetric department in Vienna, Austria, Semmelweis noticed that women delivered by physicians and medical students had a much higher mortality rate than women delivered by midwives. He concluded that the problem was that physicians were handling corpses during autopsies before attending to pregnant women, and determined that hand washing would prevent them from passing on illness.

Joseph Lister:

Antisepsis is the method of using chemicals, called antiseptics, to destroy the germs that cause infections. It was developed by the British surgeon Joseph Lister.

Photograph of Joseph Lister
Joseph Lister, 1827–1912.
Joseph Lister found a way to prevent infection in wounds during and after surgery.
He was the first to apply the science of Germ Theory to surgery.
Lister’s Antisepsis System is the basis of modern infection control.
His principles made surgery safe and continue to save countless lives.

Question 2

sterilization

Answer 2

removing all microbial life (including viruses)

Question 3

disinfection

Answer 3

Removing vegetative pathogens from inanimate surfaces. But not bacterial endospores. physical process or chemical agent

Question 4

antisepsis

Answer 4

a growth-inhibiting agent used on tissues to prevent infection. Removing pathogens from living tissue. Reduces the number of microbes on the human skin. A form of decontamination but on living tissues.

Question 5

Decontamination

Answer 5

sanitization

Question 6

Bactericide

Answer 6

Is a chemical that destroys bacteria except for those in the endospore state. It may or may not be effective on other microbial groups.

Question 7

germicide

Answer 7

An agent lethal to non-endospore-forming pathogens

Question 8

Bacteriostasis

Answer 8

Agents that prevent the growth bacteria on tissues or on objects in the environment

Question 9

sanitization

Answer 9

cleansing technique that mechanically removes microorganisms as well as other debris to reduce contamination to safe levels

Question 10

Asepsis

Answer 10

a condition free of viable pathogenic microorganisms. Any practice that prevents the entry of infectious agents into sterile tissues and thus prevents infection.
Aseptic techniques: practiced in health care; range from sterile methods to antisepsis and disinfection.

Question 11

Indicate the 4 main factors that determine how effective an antimicrobial control method is.

Answer 11

1. Number of microbes
2. Environment (organic matter, temperature, biofilms)
3. Time of exposure
4. Microbial characteristics
   A. Some microbes have certain structural features that enable them to survive certain treatments
   B. What is one feature you have learned about that enables a bacterial species to be heat tolerant.

Question 12

Illustrate the hierarchy of microorganisms from those easiest to destroy to those most difficult to destroy (see figures in PowerPoint)

Answer 12

Prions
Bacterial endospores
mycobacterium
Protozoan trophozoites
most gram-negative bacteria
Fungi and fungal spores
nonenveloped viruses
Most gram-positive bacteria
enveloped viruses
(More resistant to least resistant)

Question 13

Compare and contrast “cidal” and “static” microbial control processes

Answer 13

-cide (kill or destroy)
bactericides
Fungicides
virucides
sporicide
Microbicides (germicide)
cidal activity depends on use

-static (stop or stand still)
Bacteristatic
fungistatic
microbistatic

Question 14

Describe the effects of microbial control agents on cellular structures. (Table 9.3 in text)

Answer 14

Cell wall: chemical agents can damage the cell wall by
-blocking its synthesis or
-digesting it
Examples: chemicals, detergents, alcohol.

Cytoplasmic membrane: agents disrupt the lipid layer of the cytoplasmic membrane. This opens up the cytoplasmic membrane and allows damaging chemicals to enter the cell and important ions to exit the cell.
Examples: detergents, alcohol.

Cellular synthesis: agents can interrupt the synthesis of proteins via the ribosomes, inhibiting proteins needed for growth and metabolism and preventing multiplication.
Examples: formaldehyde, radiation, ethylene oxide

Proteins: some agents are capable of denaturing proteins (breaking of protein bonds, which results in breakdown of the protein structure)
Agents may attach to the active site of a protein, preventing it from interacting with its chemical substrate.
examples: moist heat, alcohol, phenolics.

Question 15

Compare the effectiveness of moist heat (boiling, autoclaving, pasteurization) and dry heat.

Answer 15

Moist heat can achieve the same effectiveness as dry heat but with lower temperatures and shorter exposure times. Although many cellular structures are damaged by moist heat, its most lethal effect is the coagulation and denaturation of proteins, which quickly and permanently halts cellular metabolism.

Dry heat dehydrates the cell, removing the water necessary for metabolic reactions, and it also denatures proteins. However, the lack of water actually increases the stability of some protein conformations, necessitating the use of higher temperatures when dry heat is employed as a method of microbial control. At very high temperatures, dry heat oxidizes cells, burning them to ashes. This method is the one used in the laboratory when a loop is flamed or in industry when medical waste is incinerated.

Question 16

List several items that might be sterilized in an autoclave.

Answer 16

Glassware, cloth (surgical dressings), metallic instruments, liquids, paper, some media, and some heat-resistant plastics.

Question 17

Indicate why the steam autoclave cannot be used to sterilize everything.

Answer 17

any material that has contacted volatile or corrosive chemicals, even normally compatible materials, should not be autoclaved. Radioactive materials and anything containing mutagens, teratogens, or carcinogens should never be loaded in an autoclave.

Question 18

Indicate how you can be assured that an autoclave is working properly.

Answer 18

1. Physical: pressure and temperature recording devices,
2. Chemical: indicators that change color after being exposed to specific temperatures such as temperature sensitive tape. The color change upon exposure to the given temperature and
3. Biological: Bacillus stearothermophilus spores are used, due to its resistance to heat, for the testing that measures the biological performance of the autoclave process.

Question 19

List the 2 goals of pasteurization.

Answer 19

1. Destroy/remove pathogenic microorganisms
2. Extend the shelf life by reducing spoilage organisms

Question 20

Compare pasteurization (classic and HTST) to UHT. What is accomplished by UHT that is not accomplished by either pasteurization method.

Answer 20

Classic pasteurization 71.6 degrees for 15 sec

Flash pasteurization: also known as high temperature short time (HTST) pasteurization. 63 degrees yo 66 degrees C for 30 min

Ultra-high temperature (UHT) pasteurization: Heat the milk to between 135°C to 140°C for 2 to 4 seconds. The treatment also destroys most of the microorganisms that cause spoilage and so prolongs the storage time of food. Ultra-high-temperature (UHT) pasteurization involves heating milk or cream to 138–150 °C (280–302 °F) for one or two seconds.

Question 21

Define (equivalent treatments) and provide 2 examples.

Answer 21

1. Classic pasteurization (batch)
   63 C for 30 min
2. High-temperature short time (flash)
   72 C for 15 sec.
   Thermoduric organisms survive pasteurization
   Pasteurization does not sterilize.

Ultra-high temperature (UHT) Treatment
140 C for < 1 sec
This technique actually sterilizes the product
dairy products treated with UHT can be stored in sealed containers at room temperature (this is NOT a type of pasteurization!!)

Question 21

Describe how filtration, low temperatures, desiccation, and osmotic pressure suppress microbial growth.

Answer 21

Desiccation:
- vegetative cells directly exposed to normal room temperature gradually become dehydrated
- some microbes are killed by desiccation; many others are not killed and some are preserved

Lyophilization:
-combination of freezing and drying
-method of preserving microorganisms in a viable state for many years
-pure cultures are frozen instantaneously and exposed to a vacuum that removes water, avoiding the formation of ice crystals

Filtration:
-used to prepare liquids that cannot withstand heat such as serum, blood products, vaccines, drugs, IV fluids, enzymes, and milk. Alternative method for decontaminating milk and beer. Important step in water purification
-unable to remove soluble molecules (toxins) that cause disease
-high efficiency particulate air (HEPA) filters are used in hospital rooms and sterile rooms

Osmotic pressure:
-adding large amounts of salt or sugar to foods creates a hypertonic environment for bacteria, causing plasmolysis.
-pickling, smoking, and drying foods have been used for centuries to preserve foods
-never a sterilizing technique.

Question 21

Know time/temp for steam autoclave, hot air sterilization, classic pasteurization, HTST pasteurization

Answer 21

Steam autoclave: 121 degrees C 15 psi 15 min
Hot air sterilization: 150 degrees C to 180 degrees C 2 to 4 hours
Classic pasteurization: 63 C for 30 min
High-temperature short-time: 72 C for 15 sec.

Question 21

Indicate what sort of materials might be filter sterilized

Answer 21

Filtration is used to prepare liquids that cannot withstand heat, including serum and other blood products, vaccines, drugs, iv fluids, enzymes, and media. Is an alternative method for decontaminating milk and beer without altering their flavor. It is an important step in water purification.

Question 21

Explain how radiation (ionizing radiation, as well as UV radiation) kills cells.

Answer 21

Ionizing radiation: -highly effective alternative for sterilizing materials that are sensitive to heat or chemicals. Devices that emit ionizing rays include gamma-ray machines containing radioactive cobalt, x-ray machines similar to those used in medical diagnosis, and cathode ray machines. The dosage of radiation is measure in Grays. Non ionizing radiation: Ultraviolet radiation ranges in wavelength from approximately 100 to 400 nm. It is most lethal from 240 to 280 nm (with a peak of 260 nm). Owing to its lower energy state, UV radiation is not as penetrating as ionizing radiation. Because uv radiation passes readily through air, slightly through liquids, and only poorly through solids, the object to be disinfected must be directly exposed to it for full effect. Ultraviolet ray are a powerful tool for destroying fungal cells and spores, bacterial vegetative cells, protozoa, and viruses. Bacterial spores are about 10 times more resistant to radiation than are vegetative cells, but they can be killed by increasing the time of exposure. Even though it is possible to sterilize with uv, it is so technically challenging that we don’t regularly call it a sterilizing technology.

Question 21

List appropriate applications of ionizing and UV radiation for sterilization.

Answer 21

Ionizing radiation: -drugs, vaccines, medical instruments (especially plastics), syringes, surgical gloves, tissues such as bone and skin, and heart valves. - causes formation of free radicals that damages DNA Nonionizing radiation (UV, 260 nm) -damages DNA by creating thymine dimers UV radiation: -hospital rooms, operating rooms, schools, food preparation areas, and dental offices -proved effective in reducing postoperative infections, preventing the transmission of infections by respiratory droplets, and curtailing the growth of microbes in food-processing plants and slaughterhouses.

Question 22

Identify a stretch of DNA that is susceptible to UV radiation damage.

Answer 22

UV radiation damages cells by causing the inappropriate formation of bonds between two adjacent bases on a DNA strand. It affects pyrimidines (Ts and Cs). If the new “dimers” are not repaired, they can prevent the segment of DNA from being correctly replicated or transcribed. Massive dimerization is lethal to cells.

Question 22

List the factors influence the effectiveness of chemicals used for microbial control

Answer 22

Germicides are evaluated in terms of their effectiveness in destroying microbes in medical and dental settings: -high level germicides kill endospores and can be used as sterilants -intermediate level germicides kill fungal, but not bacterial spores, resistant pathogens, and viruses. -low level germicides eliminate only vegetative bacteria, vegetative fungal cells, and some viruses Factors: -the nature of the material being treated -the degree of contamination -time of exposure -strength and chemical action of the germicide -microbial load -concentration of disinfectant -presence of organic matter (often interferes) cleaning must precede use of germicides -pH

Question 23

Describe the disk-diffusion method for testing the effectiveness of antiseptics and disinfectants.

Answer 23

The disk-diffusion method involves applying different chemicals to separate, sterile filter paper disks (Figure 13.4.1 ). The disks are then placed on an agar plate that has been inoculated with the targeted bacterium and the chemicals diffuse out of the disks into the agar where the bacteria have been inoculated. As the “lawn” of bacteria grows, zones of inhibition of microbial growth are observed as clear areas around the disks. Although there are other factors that contribute to the sizes of zones of inhibition (e.g., whether the agent is water soluble and able to diffuse in the agar), larger zones typically correlate to increased inhibition effectiveness of the chemical agent. The diameter across each zone is measured in millimeters.

Question 24

Identify preferred uses of the following chemicals: phenol, chlorhexidine, povidone iodine (Betadine), bleach and other chlorine compounds, alcohol, heavy metals (silver)

Answer 24

Phenol: -targets some bacteria, viruses, fungi -now only used in certain limited cases, such as drains, cesspools, and animal quarters -banned in 2017 including triclosan and triclocarbon Chlorhexidine: - targets most bacteria, viruses, fungi -mildness, low toxicity, and rapid action make chlorhexidine a popular choice of agents -used in hand scrubs, prepping skin for surgery, as an obstetric antiseptic, as a mucous membrane irrigant, etc. -effects on viruses and fungi are variable Alcohol: -most bacteria, viruses, fungi -germicidal, nonirritating, and inexpensive -routinely used as skin determine agents (70% to 95% solutions) -rate of evaporation decreases effectiveness -inhalation of vapors can affect the nervous system Heavy metals (silver): -some bacteria, viruses, fungi -silver nitrate solutions are used for topical germicides and ointments -may cause allergic reactions in susceptible individuals Chlorine: -can kill endospores (slowly) all other microbes Less effective if exposed to light, alkaline pH, and excess organic matter Povidone-Iodine: -antiseptic used for skin disinfection before and after surgery -minor wounds -liquid or powder

Question 25

Identify the appropriate uses for quaternary ammonium compounds and provide several examples

Answer 25

Their cationic nature makes them ideal as powerful cleaners. This makes them destroy most bacteria, some viruses, and fungi. They are stable and nontoxic. examples: Benzalkonium chloride, alkyl dimethyl benzyl ammonium chloride. Found in hand soaps, toilet cleaners and disinfectant sprays, mouthwash

Question 26

Describe appropriate uses of glutaraldehyde (cold sterilization)

Answer 26

-Can irreversibly disrupt the activity of enzymes and other proteins within the cell -kills rapidly and is broad-spectrum; used to sterilize respiratory equipment, scopes, kidney dialysis machines, dental instruments -somewhat unstable, especially with increased pH and temperature. -virucidal in 10 min -sporicidal in 3-10 hours -formaldehyde -ortho-phthaldehyde Glutaraldehyde is used as a cold sterilant to disinfect and clean heat-sensitive equipment.

Question 27

Identify chemical sterilizers

Answer 27

Alcohol, chlorine, formaldehyde, glutaraldehyde, ethylene oxide, plasma gas, iodine, phenolics, chlorhexidine, bisphenol, quats, silver.

Question 28

Describe appropriate applications of ethylene oxide sterilization.

Answer 28

uses: heat sensitive material Special gas sterilizing chamber toxic to humans - precautions Long exposure time is required (4-18 hours) very penetrating Widely used for medical supplies/equipment, disposable plastic ware, textiles, sutures, lensed instruments, implanted prosthetics, large pieces of equipment, furniture (never food items) chemical sterilant

Question 29

Describe appropriate applications of plasma gas, supercritical fluids, hydrogen peroxide

Answer 29

Plasma gas: -hydrogen peroxide is activated by a vacuum and an electromagnetic field to form plasma gas -free radicals destroy microbes -current use: tubular instruments (endoscopy equipment) -good for items that are temperature or moisture sensitive -inexpensive, relatively safe Supercritical fluids: -CO2 is compressed into a “supercritical state” with gaseous and liquid properties -use: tissue medical implants (bone, tendons, ligaments) taken from cadaver donors. H2O2-Hydrogen Peroxide: -not a good antiseptic for wounds -used to disinfect inanimate objects -used to disinfect contact lenses -hot gaseous H2O2 - used for sterilization of atmosphere and surfaces including hospital rooms (Bioquell)

Question 30

Given an item requiring disinfection of sterilization, select the most effective method/process to accomplish this.

Answer 30

steam is the preferred method for sterilizing medical and surgical

Question 31

Illustrate the hierarchy of microorganisms from those easiest to destroy to those most difficult to destroy (see figure in powerpoint)

Answer 31

Most resistant to least resistant: prions Endospores of bacteria mycobacteria Cysts of protozoa vegetative protozoa Gram-negative bacteria fungi, including most fungal spores Viruses without envelopes gram-positive bacteria Viruses with lipid envelopes

Question 32

Recognize that several bacterial species (MRSA, VRE) are very difficult to treat when a patient is infected because they are resistant to multiple antibiotics, but are READILY killed by disinfecting chemicals and treatments in the environment.

Question 33

Select the applications of ethylene oxide sterilization

Answer 33

plastics Prepackaged medical devices

Question 34

The most efficient sterilizing conditions in a steam autoclave are

Answer 34

121 C at 15 psi for 15 minutes

Question 35

From the list below, choose the two most resistant microbial forms

Answer 35

prions endospores

Question 36

Which of the following are correctly matched? Check all that apply

Answer 36

bactericidal-kills bacteria Bacteriostatic-inhibits the growth of bacteria

Question 37

ionizing and non ionizing radiation can be used in microbial control. Which of the following statements are true regarding the use of radiation

Answer 37

1. Ionizing radiation has good penetrating power 2. Ionizing radiation can be used to sterilize heat-sensitive materials 3. UV light is an example of non ionizing radiation

Question 38

Match the term with its description to test your understanding of microbial control terminology

Answer 38

Destruction of all microbial life including bacterial endospores - sterilization Reduction of most microbial life on inanimate surfaces - disinfection Reduction of most microbial life on living tissue- antisepsis Mechanical removal of most microbes from living or inanimate surfaces- decontamination

Question 39

Disinfection of beverages such as apple juice, milk, wine is optimally achieved by

Answer 39

pasteurization

Question 40

The most versatile method for sterilizing heat-sensitive liquids is

Answer 40

filtration

Question 41

Evaluate the following statements, and select those that apply to SARS-CoV-2, the enveloped virus responsible for COVID-19

Answer 41

1. It is easier to control SARS-CoV-2 than rotavirus, naked virus 2. SARS-CoV-2 represents of the least resistant microbial forms. 3. Detergents and alcohols can be effectively used against this virus

Question 42

What is the most appropriate method of sterilization for metallic surgical instruments

Answer 42

Pressurized steam

Question 43

During a surgical procedure, the RN observes a surgeon wearing sterile gloves brush his posterior hand surface on a tray. The tray had been cleaned with liquid chemical agent. What is the most appropriate action by the RN?

Answer 43

Assertion to the surgeon that change of gloves is necessary before continuing the procedure.

Question 44

which of the following microbes may still be present on sterile surgical instruments

Answer 44

prions

Question 45

What is the RN’s most appropriate action with used needles following the completion of the procedure

Answer 45

discarding

Question 46

Cytoplasmic enzymes are most likely to be disrupted by

Answer 46

high temperatures

Question 47

The advantage of using ethylene oxide as a sterilant over moist heat sterilization in an autoclave is that

Answer 47

It can be used to sterilize plastics that would melt in an autoclave

Question 48

Which of the following is not used as an antiseptic

Answer 48

Glutaraldehyde

Question 49

Microbial control methods that kill (blank) are able to sterilize

Answer 49

endospores

Question 50

The patient has a central venous line for administration of IV fluids and medications. Which of the following interventions demonstrates aseptic technique by the RN when manipulating the line

Answer 50

Cleansing line cap with alcohol swab changing dressing with sterile procedure Wearing gloves

Question 51

Which of the following agents is/are most appropriate for use for skin antisepsis when performing a routine dressing change of the central venous line

Answer 51

Alcohol and chlorhexidine

Question 52

which of the following is the most import point of teaching for visitors to prevent the patient from being exposed to other infectious agents

Answer 52

Hand hygiene by washing or antiseptic hand sanitizer application when entering and leaving room

Question 53

What is the goal of the use of a high-efficiency particulate air (HEPA) filter in the patient’s room

Answer 53

Air decontamination

Question 54

choose the method used to sterilize a loop before and after inoculating a culture in the laboratory

Answer 54

incineration

Question 55

Which of the following are physical control methods? Check all that apply

Answer 55

cold Dry and moist heat radiation dessication

Question 56

Match the chemical agent with its corresponding common application (Halogens)

Answer 56

Large-scale disinfection of drinking water - chlorine gas Disinfection in dairies, food processing plants, restaurants, hospitals, homes - hypochlorites Skin and tissue antisepsis - Iodophors

Question 57

choose the statement that identifies the major disadvantage of both cold and desiccation in terms of microbial control

Answer 57

These methods are bacteriostatic rather than bactericidal

Question 58

A(n) (blank) would be used to destroy bacteria on a countertop whereas a(n) (blank) would be used on skin prior to making an incision

Answer 58

Disinfectant; antiseptic

Question 59

the compound that is an excellent antiseptic, and is used increasingly for mucous membrane irrigation, oral rinses to control gingivitis or after invasive dental procedures (root canal, dental implant), obstetrical washes, hand scrubbing, and prepping surgical skin sites is

Answer 59

Chlorhexidine

Question 60

(Blank) is a halogen used in gaseous and liquid form for large-scale disinfection of drinking water and sewage.

Answer 60

chlorine

Question 61

Steam under pressure

Answer 61

Requires use of an autoclave. To sterilize, temperature must reach 121 C for a minimum of 15 minutes

Question 62

Boiling water

Answer 62

100 C, 30 minutes will disinfect but will not sterilize

Question 63

Pasteurization

Answer 63

Heat applied to beverages to prevent spoilage and kill pathogens. Protocols include holding liquids at 71.6 C for 15 sec or at 63 C for 30 min. Does not sterilize.

Question 64

Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperatures

Answer 64

False

Question 65

choose the microbial control method that neither inhibits nor kills microbes, but instead physically removes them from liquids or air

Answer 65

choose the microbial control method that neither inhibits nor kills microbes, but instead physically removes them from liquids or air

Question 66

Select those characteristics of a chemical control agent that make it a desirable agent

Answer 66

1. Water or alcohol soluble and stable 2. Microbicidal to a wide range of microbes, but nontoxic to humans and animal tissue 3. Rapidly effective in low concentrations 4. Inexpensive

Question 67

Disinfection procedures must take into account

Answer 67

1. The mixture of microbes being targeted 2. Whether the microbes in biofilms are dispersed 3. The amount of organic matter associated with the microbes

Question 69

Select the methods below that illustrate the use of noise heat to control microbes

Answer 69

Steam autoclave pasteurization Boiling water

Question 70

Select the advantages of phenolic compounds as antimicrobial agents

Answer 70

Remain effective in the presence of organic matter Strongly microbicidal

Question 71

Which of the following represent the cellular targets for physical and chemical control agents

Answer 71

Cell membrane cellular synthesis of DNA and RNA Proteins cell wall

Question 72

Ethylene oxide is a sterilizing gas

Answer 72

true

Question 73

Dry Heat

Answer 73

Incineration hot-air oven

Question 74

Moist Heat

Answer 74

Boiling water steam under pressure

Question 75

Radiation

Answer 75

Gamma and x-rays UV rays

Question 76

Dessication

Answer 76

Pasteurization Dehydration by exposure to normal room air

Question 77

Select the microorganism that is least resistant to chemical and physical control measures

Answer 77

Enveloped viruses