Sterilization, Disinfection, and Antisepsis

Question 1

Cross-infection:

Answer 1

Transmission of infectious agents among

patients and staff in a clinical environment

Question 2

Cross-infection control:

Answer 2

Management strategies for risk control

Question 3

Cross-infection risks in dentistry
Possible sources of infection in the dental care setting:
(4)

Answer 3

Patients with infectious disease
Patients in the prodromal or
convalescent stage of infection
Healthy (or asymptomatic) carriers
of disease-causing organisms
Environmental sources: airborne
organisms or biofilms in waterlines
or on equipment or instruments

Question 4

Universal precautions:

Answer 4

All patients are treated as though

they are a potential source of infectious pathogens.

Question 5

Airborne Routes

Examples of dust-borne routes:

Answer 5

Staphylococcus aureus from skin scales
Clostridium tetani from environmental dust
these and other organisms released from solid surfaces
sources: skin scales, wound dressings, solid surfaces

Question 6

Airborne Routes

Examples of aerosol routes:

Answer 6

large droplets (classified as contact)
droplet nuclei
sources: speaking, sneezing, all intraoral procedures.
Massive increase when using ultrasonic scaling, air-rotor,
air/water syringe.

Question 7

Prevention of aerosol transmission (2)

Answer 7

1. Elimination or limitation of organisms at source

2. Interruption of transmission

Question 8

Contact Routes

person-to-person:

Answer 8

direct spread from person-to-person by hands and clothes or
fomites (towels, etc.); large droplets (classified as contact)
prevention: hand washing, gloves, and protective clothing

Question 9

Contact Routes
equipment:
(3)

Answer 9

dental instruments
chairs
impression materials

Question 10

skipped
Contact Routes
prevention :

Answer 10

sterilization of instruments
use of disposals
disinfection of dental materials
environmental hygiene
defining zones in the dental operatory
disposal of infected waste

Question 11

Contact Routes (continued)
Fluids

Answer 11

dental water supplies
prevention: flushing water supply lines, using sterile
water, and using biocide in water

Question 12

Parenteral Spread of Cross-Infection
Sources: (3)
Inoculation: via (4)

Answer 12

blood, saliva, and secretions

eye, skin breach, mucous membrane, sharps injury

Question 13

skipped
Parenteral Spread of Cross-Infection
prevention:

Answer 13

training in use and disposal of sharps, hepatitis B

vaccination, wearing gloves, dressing wounds

Question 14

• sterilization

Answer 14

– destruction of all microbial forms (including bacterial spores)

Question 15

• disinfection

2

Answer 15

– destruction of most microbial forms
– disinfectants
• agents, usually chemical, used for disinfection
• usually used on inanimate objects
• high-level, intermediate-level, low-level

Question 16

– disinfectants

3

Answer 16

• agents, usually chemical, used for disinfection
• usually used on inanimate objects
• high-level, intermediate-level, low-level

Question 17

• antisepsis

2

Answer 17

– Inhibition or elimination of microbes on living tissue

– antiseptics

Question 18

– antiseptics

Answer 18

• chemical agents that kill or inhibit growth of microorganisms when
applied to tissue

Question 19

• sanitization

Answer 19

– reduction of microbial population to levels deemed safe (based
on public health standards)

Question 20

Antimicrobial agents

3

Answer 20

• agents that kill microorganisms or inhibit
their growth
• -cidal agents kill
• -static agents inhibit growth

Question 21

The Pattern of Microbial Death

3

Answer 21

• microorganisms are not killed instantly
• population death usually occurs
exponentially
• microorganisms are considered to be dead
when they are unable to reproduce in
conditions that normally support their
reproduction

Question 22

Once the population has
been greatly reduced the
rate of killing may slow due
to

Answer 22

resistant individuals

Question 23

Conditions Influencing the Effectiveness of
Antimicrobial Agent Activity
(6)

Answer 23

• population size
• population composition
• concentration or intensity of an antimicrobial
agent
• duration of exposure
• temperature
• local environment (e.g. pH, viscosity, etc.)

Question 24

The Use of Physical Methods in
Control
(4)

Answer 24

• heat
• low temperatures
• filtration
• radiation

Question 25

Heat • moist heat (2)

Answer 25

– effective against all types of microorganisms – degrades nucleic acids, denatures proteins, and disrupts membranes

Question 26

Heat • dry heat sterilization (2)

Answer 26

– less effective, requiring higher temperatures and longer exposure times – oxidizes cell constituents and denatures proteins

Question 27

Measuring heat-killing efficiency | • thermal death time (TDT)

Answer 27

– shortest time needed to kill all microorganisms in a suspension at a specific temperature and under defined conditions

Question 28

Measuring heat-killing efficiency | • decimal reduction time (D or D value)

Answer 28

– time required to kill 90% of microorganisms or spores | in a sample at a specific temperature

Question 29

• Z value

Answer 29

– increase in temperature required to reduce D to 10% of original value

Question 30

Autoclaves | 2

Answer 30

– used to kill endospores efficiently – use saturated steam under pressure to reach temperatures above boiling

Question 31

Moist heat • pasteurization (2)

Answer 31

– controlled heating at temperatures well below boiling – reduces total microbial population and thereby increases shelf life of treated material

Question 32

Pasteurization of milk | 2

Answer 32

•flash pasteurization (high temperature short-term – HTST) –72oC for 15 seconds then rapid cooling •ultrahigh-temperature (UHT) sterilization –140 to 150oC for 1 to 3 seconds

Question 33

Low Temperatures • freezing (2)

Answer 33

– stops microbial reproduction due to lack of liquid water – some microorganisms killed by ice crystal disruption of cell membranes

Question 34

Low Temperatures | • refrigeration

Answer 34

– slows microbial growth and reproduction

Question 35

Filtration | 2

Answer 35

• reduces microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms • also used to reduce microbial populations in air

Question 36

Filtering liquids | • depth filters

Answer 36

– thick fibrous or granular filters that remove microorganisms by physical screening, entrapment, and/or adsorption

Question 37

Filtering liquids | • membrane filters

Answer 37

– porous membranes with defined pore sizes that remove microorganisms primarily by physical screening

Question 38

Filtering air (2)

Answer 38

• surgical masks • high-efficiency particulate air (HEPA) filters

Question 39

Radiation | • ultraviolet (UV) radiation

Answer 39

– limited to surface sterilization because UV radiation does not penetrate glass, dirt films, water, and other substances

Question 40

Radiation • ionizing radiation (3)

Answer 40

– penetrates deep into objects – destroys bacterial endospores; not always effective against viruses – used for sterilization and pasteurization of antibiotics, hormones, sutures, plastic disposable supplies, and food

Question 41

Phenolics | 4

Answer 41

• commonly used as laboratory and hospital disinfectants (Lysol is a mixture of phenolics) • act by denaturing proteins and disrupting cell membranes • tuberculocidal, effective in presence of organic material, and long lasting • disagreeable odor and can cause skin irritation

Question 42

Alcohols | 4

Answer 42

• bactericidal, fungicidal, but not sporicidal • inactivate some viruses • denature proteins and possibly dissolve membrane lipids • 60%-90% in water (cidal activity drops sharply when diluted below 50% concentration)

Question 43

Halogens | contain (4)

Answer 43

fluorine, chlorine, bromine, iodine

Question 44

Halogens • Iodine (5)

Answer 44

-skin antiseptic -oxidizes cell constituents and iodinates proteins -at high concentrations may kill spores -skin damage, staining, and allergies can be a problem -iodophore (iodine complexed with organic carrier)

Question 45

Halogens • Chlorine (4)

Answer 45

-oxidizes cell constituents -important in disinfection of water supplies and swimming pools, used in dairy and food industries, effective household disinfectant -destroys vegetative bacteria and fungi, but not spores -can react with organic matter to form carcinogenic compounds

Question 46

Heavy Metals | 3

Answer 46

• e.g., ions of mercury, silver, arsenic, zinc, and copper • effective but usually toxic • combine with and inactivate proteins; may also precipitate proteins

Question 47

Quaternary Ammonium Compounds • detergents (2)

Answer 47

– organic molecules with hydrophilic and hydrophobic ends – act as wetting agents and emulsifiers

Question 48

Quaternary Ammonium cationic detergents are effective disinfectants (2)

Answer 48

– kill most bacteria, but not Mycobacterium tuberculosis or endospores – safe and easy to use, but inactivated by hard water and soap

Question 49

Aldehydes (3)

Answer 49

highly reactive molecules • sporicidal and can be used as chemical sterilants • combine with and inactivate nucleic acids and proteins

Question 50

Sterilizing Gases (3)

Answer 50

* used to sterilize heat-sensitive materials * microbicidal and sporicidal * combine with and inactivate proteins

Question 51

Category: Critical Level: Risk: Objects:

Answer 51

``` Heat Sterilization Very high Touch bone or penetrate tissue; blood present (scalpels, forceps, scalers, probes, implants) ```

Question 52

Category: Semi-Critical Level: Risk: Objects:

Answer 52

Sterilization, High-level disinfection Moderate Touch mucous membrane but not penetrate; no blood, (mirrors, burnishers, amalgam carriers, etc.)

Question 53

Category: Non-Critical Level: Risk: Objects:

Answer 53

Intermediate level Low Unbroken skin contact; no blood; (masks, clothing. Blood pressure cuffs)

Question 54

Category: Environmental surfaces Level: Risk: Objects:

Answer 54

``` Low level disinfection; sanitation Minimal No direct patient contact, no blood; (door knobs, floors, walls, counters, mops and other housekeeping equipment) ```