Sterilization, Disinfection, and Antisepsis Flashcards
Cross-infection:
Transmission of infectious agents among
patients and staff in a clinical environment
Cross-infection control: l
Management strategies for risk control
Cross-infection risks in dentistry
Possible sources of infection in the dental care setting:
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
Universal precautions:
All patients are treated as though
they are a potential source of infectious pathogens.
Airborne Routes
dust vs aerosol borne?
examples?
when is aerosol increased?
Examples of dust-borne routes:
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
Examples of aerosol routes:
large droplets (classified as contact)
droplet nuclei
sources: speaking, sneezing, all intraoral procedures.
Massive increase when using ultrasonic scaling, air-rotor, air/water syringe.
Prevention of aerosol transmission
- Elimination or limitation of organisms at source
2. Interruption of transmission
Contact Routes, preventions
person-to-person:
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
equipment: dental instruments, chairs, impression materials prevention : sterilization of instruments use of disposals disinfection of dental materials environmental hygiene defining zones in the dental operatory disposal of infected waste
Fluids
dental water supplies
prevention: flushing water supply lines, using sterile water, and using biocide in water
Parenteral Spread of Cross-Infection
sources
innoculation
prevention
Sources: blood, saliva, and secretions
Inoculation: via eye, skin breach, mucous membrane, sharps injury
prevention: training in use and disposal of sharps, hepatitis B vaccination, wearing gloves, dressing wounds
sterilization
– destruction of all microbial forms (including bacterial spores)
disinfection
agents of this? mainly?
used on?
levels?
– destruction of most microbial forms
– disinfectants
• agents, usually chemical, used for disinfection
• usually used on inanimate objects
• high-level, intermediate-level, low-level
antisepsis
– Inhibition or elimination of microbes on living tissue
– antiseptics
• chemical agents that kill or inhibit growth of microorganisms when
applied to tissue
sanitization
– reduction of microbial population to levels deemed safe (based
on public health standards)
Antimicrobial agents
• agents that kill microorganisms or inhibit
their growth
• -cidal agents kill
• -static agents inhibit growth
The Pattern of Microbial Death
- 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
rate of microbial killing with time
Once the population has been greatly reduced the rate of killing may slow due to resistant individuals.
Conditions Influencing the Effectiveness of Antimicrobial Agent Activity
- population size
- population composition
- concentration or intensity of an antimicrobial agent
- duration of exposure
- temperature
- local environment (e.g. pH, viscosity, etc.)
The Use of Physical Methods in Control
- heat
- low temperatures
- filtration
- radiation
• moist heat
– effective against all types of microorganisms
– degrades nucleic acids, denatures proteins, and
disrupts membranes
• dry heat sterilization
– less effective, requiring higher temperatures and
longer exposure times
– oxidizes cell constituents and denatures proteins
Measuring heat-killing efficiency, values?
• thermal death time (TDT)
– shortest time needed to kill all microorganisms in a suspension at a specific temperature and under defined conditions
• decimal reduction time (D or D value)
– time required to kill 90% of microorganisms or spores in a sample at a specific temperature
Z value
– increase in temperature
required to reduce D to
10% of original value
Autoclaves
type of moist heat
– used to kill endospores efficiently
– use saturated steam under pressure to reach temperatures above boiling
Moist heat- pasteurization, milk?
– controlled heating at temperatures well below boiling
– reduces total microbial population and thereby increases shelf life of treated material
Pasteurization of milk
•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
Low Temperatures (freezing and refrigeration)
• freezing
– stops microbial reproduction due to lack of liquid water
– some microorganisms killed by ice crystal disruption of cell membranes
• refrigeration
– slows microbial growth and reproduction
Filtration
- reduces microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms
- also used to reduce microbial populations in air
Filtering liquids, types of filters?
• depth filters
– thick fibrous or granular filters that remove microorganisms by physical screening, entrapment, and/or adsorption
• membrane filters
– porous membranes with defined pore sizes that remove microorganisms primarily by physical screening
Filtering air tools
- surgical masks
* high-efficiency particulate air (HEPA) filters
Radiation types
UV and ionizing
ultraviolet (UV) radiation
– limited to surface sterilization because UV radiation
does not penetrate glass, dirt films, water, and other
substance
ionizing radiation
– 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
Phenolics
commonly used where?
mechanism?
problems?
phenol, hexochlorophene
• 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
Alcohols
work on?
mechanism?
concentration?
ethanol, isopropanol
• 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)
Halogens
contain fluorine, chlorine, bromine, iodine
Iodine primary use? mechanism? high concentrations? issues? iodophores?
- 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)
Chlorine mechanism? important where? can/cannot destroy? carcinogen?
- 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
Heavy Metals
- e.g., ions of mercury, silver, arsenic, zinc, and copper
- effective but usually toxic
- combine with and inactivate proteins; may also precipitate proteins
Quaternary Ammonium
Compounds
cetylpyridium chloride, benzalkonium chloride
• detergents
– organic molecules with hydrophilic and hydrophobic ends
– act as wetting agents and emulsifiers
• cationic detergents are effective disinfectants
– kill most bacteria, but not Mycobacterium tuberculosis or endospores
– safe and easy to use, but inactivated by hard water and soap
Aldehydes
reactivity?
spores?
mechanism?
- highly reactive molecules
- sporicidal and can be used as chemical sterilants
- combine with and inactivate nucleic acids and proteins
Sterilizing Gases
used for?
-cidal towards?
mechanism?
ethlyene oxide, betaproprionelactone
• used to sterilize heat-sensitive materials
• microbicidal and sporicidal
• combine with and inactivate proteins
Spaulding Inanimate Objects Classification
