Sterilization and Disinfectant Flashcards
Transmission of infectious agents among patients and staff in a clinical environment
Cross-infection
Management strategies for risk control
Cross-infection control:
All patients are treated as though they are a potential source of infectious pathogens.
Universal precautions
What are some routes of spread for cross-infection?
Airborne Routes
Contact Routes
Parenteral Spread of Cross-Infection
- 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
dust-bourne 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.
aerosol routes
steps in the prevention of _____ _____
- Elimination or limitation of organisms at source
- Interruption of transmission
aerosol transmission
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
person-to-person: contact route
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
Equipment
dental water supplies
prevention: flushing water supply lines, using sterile
water, and using biocide in water
fluids: contact routes
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
Parenteral Spread of Cross-infection
– destruction of all microbial forms (including bacterial spores)
sterilization
– destruction of most microbial forms
– disinfectants
• agents, usually chemical, used for disinfection • usually used on inanimate objects • high-level, intermediate-level, low-level
disinfection
– Inhibition or elimination of microbes on living tissue
– antiseptics
• chemical agents that kill or inhibit growth of microorganisms when
applied to tissue
antisepsis
– reduction of microbial population to levels deemed safe (based
on public health standards)
sanitization
• agents that kill microorganisms or inhibit
their growth
Anti microbial agents
• -cidal
agents kill
• -static
agents inhibit growth
• 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
T he Pattern of Microbial Death
• population size
• population composition
• concentration or intensity of an antimicrobial
agent
• duration of exposure
• temperature
• local environment (e.g. pH, viscosity, etc.)
Conditions Influencing the Effectiveness of Antimicrobial Agent Activity
• heat • low temperatures • filtration • radiation
Physical Methods used in Control
– effective against all types of microorganisms
– degrades nucleic acids, denatures proteins, and
disrupts membranes
moist heat
– less effective, requiring higher temperatures and
longer exposure times – oxidizes cell constituents and denatures proteins
dry heat sterilization
– shortest time needed to kill all microorganisms in a
suspension at a specific temperature and under defined conditions
thermal death time (TDT)
– time required to kill 90% of microorganisms or spores
in a sample at a specific temperature
decimal reduction time (D or D value)
– increase in temperature
required to reduce D to 10% of original value
z value
– used to kill endospores efficiently – use saturated steam under pressure to reach temperatures above boiling
autoclaves
– controlled heating at temperatures well below
boiling
– reduces total microbial population and thereby
increases shelf life of treated material
pasteurization
•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
Pasteurization of milk
– stops microbial reproduction due to lack of
liquid water
– some microorganisms killed by ice crystal
disruption of cell membranes
freezing
– slows microbial growth and reproduction
refrigeration
• reduces microbial population or sterilizes
solutions of heat-sensitive materials by
removing microorganisms • also used to reduce microbial populations
in air
filtration
– thick fibrous or granular filters that remove microorganisms by physical screening, entrapment, and/or adsorption
depth filters
– porous membranes with defined pore sizes that remove microorganisms primarily by physical
screening
membrane filters
• high-efficiency
particulate air (HEPA)
filters
• surgical masks
both function to
filter air
– limited to surface sterilization because UV radiation
does not penetrate glass, dirt films, water, and other substances
ultraviolet (UV) 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
ionizing radiation
• 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
Phenolics
- 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)
Alcohols
contain fluorine, chlorine, bromine, iodine
halogens
- 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)
iodine
- 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 carchinogenic compunds
chlorine
• e.g., ions of mercury, silver, arsenic, zinc,
and copper
• effective but usually toxic
• combine with and inactivate proteins; may also precipitate proteins
heavy metals
cetylpyridinium chloride
benzalkonium chloride
Qua ternary Ammonium Compounds
• 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
Qua ternary Ammonium Compounds
– kill most bacteria, but not Mycobacterium tuberculosis
or endospores
– safe and easy to use, but inactivated by hard water and soap
• cationic detergents are effective disinfectants
– organic molecules with hydrophilic and hydrophobic
ends
– act as wetting agents and emulsifiers
• detergents
• highly reactive molecules
• sporicidal and can be used as chemical sterilants
• combine with and inactivate nucleic acids and
proteins
ex. formaldehyde pr glutaraldehyde
aldehydes
- used to sterilize heat-sensitive materials
- microbicidal and sporicidal
- combine with and inactivate proteins
Sterilizing Gases
