Chapter 9: Sterilization, Disinfection, and Antisepsis

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1

The total destruction of all microbes by heat, gases, or chemicals.

sterilization

2

Autoclaving involves the exposure of suitable materials to moist heat under a pressure of 15 lb/in2 at what temperature and for how long?

  1. 121°C to 132°C for at least 15 minutes
  2. 160°C for 2 hours or 171°C for 1 hour
  3. 50°C to 60°C for 4 to 6 hours

a. 121 °C to 132°C for at least 15 minutes

3

The functionality of the autoclave should be checked routinely by including a ampule of Bacillus stearothermophilus spores and incubating it after autoclaving at 37°C in a supplied medium. What result would indicate an error in the sterilization process?

If there is an error in the sterilization process, the spores germinate and grow, producing a turbid suspension. If sterilization is successful, the incubation medium is clear.

4

Dry heat treatment for sterilization of heat-resistant instruments involves exposure to what temperature and for how long?

  1. 50°C to 60°C for 4 to 6 hours
  2. 121 °C to 132°C for at least 15 minutes
  3. 160°C for 2 hours or 171°C for 1 hour

c. 160°C for 2 hours or 171°C for 1 hour

5

Destruction of most microorganisms, but not necessarily bacterial spores or some resistant organisms.

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disinfection

6

Disinfection is the use of physical or chemical methods to destroy most microorganisms. What are the three different levels of disinfection?

  1. High-level disinfection can usually emulate the efficiency of sterilization.
  2. Intermediate-level disinfection usually does not kill bacterial spores.
  3. Low-level disinfection kills vegetative bacteria and lipid-enveloped viruses.
7

High-level disinfection can usually emulate the efficiency of sterilization. Which of the following are considered high-level disinfectants?

  1. glutaraldehyde
  2. alcohol
  3. phenolic compounds
  4. peracetic acid
  5. chlorine compounds
  6. iodophor compounds
  7. hydrogen peroxide

(a) glutaraldehyde, (d) peracetic acid, (e) chlorine, and (g) hydrogen peroxide

8

Intermediate-level disinfectants kill all microbial pathogens except bacterial spores. Which of the following are considered intermediate-level disinfectants?

  1. formaldehyde
  2. ammonium
  3. phenolic compounds
  4. alcohols
  5. hydrogen peroxide
  6. peracetic acid
  7. iodophor compounds

(c) phenolic compounds, (d) alcohols, and (g) iodophor compounds

9

The use of chemical agents on living tissue to inhibit or eliminate microbes.

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antisepsis

10

Which antiseptic agents are active against all groups of organisms except spores at concentrations of 70%−90%?

  1. iodophors
  2. alcohols
  3. phenols
  4. chlorhexidine

b. alcohols

Ethyl and isopropyl alcohol at concentrations in the range 70%-90% are active against all groups of organisms, but not spores.

11

Which antiseptic agents, at a concentration of 1−2 mg/L, have a range of activity similar to that of alcohols on the skin?

  1. triclosan
  2. phenols
  3. iodophors
  4. alcohols

c. iodophors

Iodophors at 1 to 2 mg free iodine/liter are effective antiseptic agents on the skin, having a range of activity similar to that of alcohols.

12

Which antiseptic agent has limited activity against gram-positive bacteria and is included in liquid soaps because it is nontoxic and persistent?

  1. triclosan
  2. alcohols
  3. parachlorometaxylenol
  4. chlorhexidine

c. parachlorometaxylenol

Parachlorometaxylenol has limited activity against Gram-positive bacteria and is included in liquid soaps because it is nontoxic and persistent.

13

Which antiseptic agent is active against bacteria and is used in deodorant soaps and some toothpastes?

  1. alcohols
  2. triclosan
  3. parachlorometaxylenol
  4. phenols

b. triclosan

Ultraviolet radiation can convert triclosan into polychlorinated dibenzodioxin, which has many toxic effects in humans.

14

Which is original antiseptic used by Joseph Lister to treat wound infections in the 19th century, which denatures proteins and disrupts lipidic membranes?

  1. alcohols
  2. chlorhexidine
  3. parachlorometaxylenol
  4. phenols

d. phenols

Phenols denature proteins and disrupt lipidic membranes. The phenol paracresol was the original Lysol disinfectant.

15

Which of the following is used as a hand and skin antiseptic and is often prescribed as an antiseptic in dentistry?

  1. triclosan
  2. chlorhexidine
  3. parachlorometaxylenol
  4. alcohols

b. chlorhexidine

Chlorhexidine may be used as an alternative to mechanical oral hygiene after an oral surgical procedure or as a preoperative rinse.

16

Chlorhexidine is often prescribed as an antiseptic in dentistry. Which of the following is NOT true about chlorhexidine?

  1. persistent antibacterial activity
  2. broad spectrum of action
  3. effective against S. mutans
  4. negatively charged
  5. all of the above are true

d. negatively charged

Chlorhexidine is POSITIVELY charged and neutralized by anionic detergents and soaps. Chlorhexidine inhibits a number of bacterial processes:

  1. sugar transport in streptococci
  2. amino acid uptake in S. sanguinis
  3. proteases in P. gingivalis
  4. membrane functions in streptococci
  5. binding of plaque-forming bacteria

S. mutans are especially susceptible to the activity of chlorhexidine.

17

Alkylating agents inactivate proteins by attaching short chains of carbons (alkyl groups). Which of the following are alkylating agents?

  1. formaldehyde
  2. isopropanol
  3. glutaraldehyde
  4. hydrogen peroxide
  5. ethylene oxide
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(a) formaldehyde, (c) glutaraldehyde, and (e) ethylene oxide

Formaldehyde and glutaraldehyde are used as sterilizing agents or high-level disinfectants. Glutaraldehyde is less toxic than formaldehyde.

18

Formaldehyde and glutaraldehyde are used as sterilizing agents or high-level disinfectants. What is the concentration of formaldehyde in formalin?

  1. 12%
  2. 25%
  3. 37%
  4. 43%
  5. 57%

c. 37%

Formaldehyde can be toxic to the skin or mucous membranes. The microbicidal activity of formaldehyde can be enhanced by combining it with alcohol.

19

Because glutaraldehyde is inactivated by organic material, items to be disinfected must be cleaned first.

  1. both the statement and the reason are correct
  2. the statement is correct, but the reason is not
  3. the reason is correct, but the statement is not
  4. neight the statement nor the reason are correct

a. both the statement and the reason are correct

Glutaraldehyde becomes polymerized in solution and interacts with amino acids in proteins or peptidoglycan, thereby inactivating them.

20

Which of the following is a a colorless, flammable, and potentially explosive gas used to sterilize heat-sensitive items?

  1. formaldehyde
  2. carbon dioxide
  3. glutaraldehyde
  4. ethylene oxide
  5. carbon monoxide

d. ethylene oxide

Ethylene oxide inactivates microorganisms by replacing hydrogen atoms in biomolecules, particularly adenine and guanine.

21

Sterilizers using ethylene oxide use 10% of the gas mixed with carbon dioxide, with an optimal relative humidity of about 30%, at:

  1. 50°C to 60°C for 4 to 6 hours
  2. 121 °C to 132°C for at least 15 minutes
  3. 160°C for 2 hours or 171°C for 1 hour

a. 50°C to 60°C for 4 to 6 hours

Since ethylene oxide is toxic, the chamber must be aerated for at least 16 hours to prevent tissue damage from absorbed gas on the material.

22

Oxidizing agents oxidize functional groups on proteins and thereby inactivate them. Which of the following are oxidizing agents?

  1. iodine
  2. chlorine
  3. benzalkonium chloride
  4. ethylene oxide
  5. hydrogen peroxide

(a) iodine, (b) chlorine, and (e) hydrogen peroxide

Ethylene oxide (d) is an alkylating agent used to sterilize heat-sensitive items. Benzalkonium chloride (c) is a quaternary ammonium salt.

23

Which of the following can be combined with a carrier compound such as polyvinylpyrrolidone to form a complex is termed an iodophor?

  1. iodine
  2. chlorine
  3. benzalkonium chloride
  4. ethylene oxide
  5. hydrogen peroxide

a. iodine

Iodine was originally used as a 2% solution in 50% alcohol, which sometimes caused hypersensitivity reactions.

24

Which of the following can can oxidize irreversibly sulfhydryl groups of proteins and has greater activity under acidic conditions?

  1. benzalkonium chloride
  2. cetylpyridinium chloride
  3. chlorine
  4. ethanol
  5. iodine

c. chlorine

Chlorine in water may be found as hypochlorous acid (HOCI), hypochlorite ion (ClOi, or elemental chlorine:

  1. chlorine can oxidize irreversibly sulfhydryl groups of proteins
  2. hypochlorite ions form toxic N-chloro compounds in the cytoplasm

Chlorine has greater activity under acidic conditions, indicating that hypochlorous acid is the more active substance compared with hypochlorite ion.

25

Hydrogen peroxide as a ___% solution in water acts as an antiseptic. In the range ___%, it can kill most bacteria, and in the range ___%, it can destroy spores.

  1. 1%; 2−3%; 6%
  2. 3%; 3−6%; 10−25%
  3. 3%: 6−10%; 10−25%
  4. 6%: 10−25%; 57%

b. 3%; 3−6%; 10−25%

The active form of hydrogen peroxide is the free hydroxyl radical (ΌΗ) formed by the decomposition of hydrogen peroxide.

26

Surfactants are amphipathic molecules that can alter bacterial cell membranes and cause leakage of intracellular ions and compounds. Which of the following act as surfactants?

  1. benzalkonium chloride
  2. cetylpyridinium chloride
  3. chlorine
  4. ethanol
  5. iodine

(a) benzalkonium chloride and (b) cetylpyridinium chloride

Benzalkonium chloride and cetylpyridinium chloride are examples of quaternary ammonium salts. They are safe to use on skin at concentrations of 0.1%.

27

Alcohols can disrupt the membrane lipids of microorganisms and denature proteins. Which of the following are alcohols?

  1. iodine
  2. chlorine
  3. isopropanol
  4. ethanol
  5. metoprolol

(d) ethanol and (e) isopropanol

Ethanol and isopropanol are the two most commonly used alcohols and have activity against vegetative bacteria, mycobacteria, fungi, and viruses.

28

70% alcohol is more active than 95% alcohol, because membrane lipids are disrupted more efficiently in the presence of water.

  1. both the statement and the reason are correct
  2. the statement is correct, but the reason is not
  3. the reason is correct, but the statement is not
  4. neither the statement nor the reason are correct

b. the statement is correct, but the reason is not

Alcohol activity is greater in the presence of water because PROTEINS are denatured more efficiently in the presence of water.