desinfectives and antispetics Flashcards
Disinfection
thermal or chemical destruction of pathogenic and other types of microorganisms
less lethal than sterilization because it destroys most recognized pathogenic microorganisms but not necessarily all microbial forms (e.g., bacterial spores)
Disinfectant
usually a chemical agent (but sometimes a physical agent) that destroys disease-causing pathogens or other harmful microorganisms but might not kill bacterial spores
Refers to substances applied to inanimate objects (surfaces)
Use on inanimate objects
Sterilants
kill both vegetative cells and spores
Disinfection can be accomplished by
chemical agents
physical agents
- as ionizing radiation
- dry or moist heat
- superheated steam (autoclave, 120°C)
combination
Antiseptic and asepsis
substance that prevents or arrests the growth or action of microorganisms by inhibiting their activity or by destroying them
the term is used especially for preparations applied topically to living tissue (skin, mucous membranes, or wounds)
Asepsis: prevention of contact with microorganisms
Use on skin
Bacteriostatic
capable of inhibiting the growth or reproduction of bacteria
Bactericide
agent that kills bacteria
Sterile or Sterility
state of being free from all living microorganisms
Prevention of infection also can be achieved by
Washing
-dilutes the potentially infectious organism
establishing a barrier
-gloves
Hand hygiene is the most important means of preventing transmission of infectious agents!!!!
Properties of an ideal disinfectant
Broad spectrum: wide antimicrobial spectrum
Fast acting: rapid kill
Not affected by environmental factors:
active in the presence of organic matter (e.g., blood, sputum, feces)
compatible with soaps, detergents, and other chemicals encountered in use
Nontoxic: should not be harmful to the user or patient
Surface compatibility:
should not corrode instruments and metallic surfaces
should not cause the deterioration of cloth, rubber, plastics, and other materials
Residual effect on treated surfaces: should leave an antimicrobial film on the treated surface
Odorless: pleasant odor or no odor
Economical: low cost
Solubility: should be soluble in water
Stability: should be stable in concentrate and use-dilution
Cleaner: should have good cleaning properties
Environmentally friendly: should not damage the environment on disposal
Antiseptic and disinfectant
alcohols chlorhexidine halogens: iodine, iodophors peroxygencompounds heavy metals
just disinfectant
halogens: chlorine
Phenolics
quaternary ammonium compouns
aldehydes
Alcohols
most frequently used for antisepsis and disinfection are ethanol and isopropyl alcohol (isopropanol)
Mechanism: they act by denaturation of proteins
optimum bactericidal concentration is 60–90% by volume in water
Use of alcohol-based hand rubs has been shown to reduce transmission of health care-associated bacterial pathogens
Pro:
No instrument impairment (no corrosive effects on metal instruments)
Con:
- flammable and explosive
- not sporicidal (not used as sterilants), no effect on parasites and spores
- skin-drying effect
Chlorhexidine
Mechanism:kills by disrupting the cell membrane
against vegetative bacteria and mycobacteria and has moderate activity against fungi and viruses
mouthwash
The combination of chlorhexidine gluconate in 70% alcohol is the preferred agent for skin antisepsis in many surgical and percutaneous procedures
The advantage of this combination over povidone-iodine
- more rapid action after application
- retained activity after exposure to body fluids
- persistent activity on the skin
Pro:
- very low skin-sensitizing or irritating capacity (component of creams, soaps, mouthwashs)
- resistant to inhibition by blood and organic materials
Con
- neural toxicity
- Elongated application may alter the oral flora
Iodine
bactericidal in 1 minute and kills spores in 15 minutes
Tincture of iodine (2% iodine and 2.4% sodium iodide in alcohol)
not commonly used
- serious hypersensitivity reactions
- staining of clothing and dressings
Iodophores
complexes of iodine with a surface-active agent such as polyvinyl pyrrolidone (PVP; povidone-iodine)
kill vegetative bacteria, mycobacteria, fungi, and lipid-containing viruses
may be sporicidal upon prolonged exposure
can be used as antiseptics or disinfectants
(Betadine)
surgical antiseptic
less irritating and less likely to produce skin hypersensitivity than tincture of iodine
Pro:
a somewhat broader spectrum of activity than chlorhexidine- including sporicidal action
Con
- lack its persistent activity on skin
- require time on skin before becoming active
Chlorine
strong oxidizing agent and universal disinfectant
most commonly provided as a 5.25% sodium hypochlorite solution (household bleach )
disinfection of blood spills
Alternative chlorine-releasing compounds include chlorine dioxide and chloramine T
-These agents retain chlorine longer and have a prolonged bactericidal action
Pro:
strong disinfectant effect
Con
- Frequent opening and closing of the container reduces the activity markedly
- inactivated by blood, serum, feces, and protein-containing materials - surfaces should be cleaned before use
- Corrosive to aluminum, silver, and stainless steel
autooxidized in contact with air
Phenolics
oldest surgical antiseptics
bactericidal (including mycobacteria), fungicidal viricidal, NOT sporicidal
no longer used
- corrosive effect on tissues
- toxicity when absorbed
- carcinogenic effect
These adverse actions are diminished by forming derivatives (o-phenylphenol, o-benzyl-p-chlorophenol, and p-tertiary amylphenol)
used for hard surface decontamination in hospitals and laboratories (floors, beds, and counter or bench top)
Con:
Skin absorption and skin irritation still occur with derivatives
Quaternary ammonium compounds (“quats”)
surface-active detergents
widely used as disinfectants
Mechanism: to inactivation of energy-producing enzymes, denaturation of proteins, and disruption of the cell membrane
used for sanitation of noncritical surfaces (floors, bench tops, furniture, and walls, equipment that contacts intact skin (blood pressure cuffs))
Spaulding classification
not important
The system classifies a medical device as critical, semicritical, or noncritical on the basis of:
- risk to patient safety from contamination on a device
- strategy for reprocessing contaminated medical devices
Critical Items
not important
confer a high risk for infection if they are contaminated with any microorganism
- objects that enter sterile tissue or the vascular system
- must be sterile
- surgical instruments, cardiac and urinary catheters, implants, and ultrasound probes used in sterile body cavities
Semicritical Items
not important
contact mucous membranes or nonintact skin
- respiratory therapy and anesthesia equipment, some endoscopes, laryngoscope blades, cystoscopes…
- small numbers of bacterial spores are permissible
- Glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde, and peracetic acid with hydrogen peroxide
Noncritical Items
not important
come in contact with intact skin but not mucous membranes
bedpans, blood pressure cuffs, crutches and computers
Aldehydes
Formaldehyde, glutaraldehyde, Ortho-phthalaldehyde
used for disinfection or sterilization of instruments such as fiberoptic endoscopes, respiratory therapy equipment, hemodialyzers, and dental handpieces that cannot withstand exposure to the high temperatures of steam sterilization
Pro:
- not corrosive for metal, plastic, or rubber
- broad spectrum of activity (bactericidal, sporicidal, fungicidal)
Con:
- Failure of disinfection due to presence of organic material
- formaldehyde is a potential carcinogen, highly irritating to respiratory mucous membranes and eyes
- Protection of health care workers is needed (Ortho-phthalaldehyde is safe)
disrupt proteins?
Peroxygen compounds
hydrogen peroxide and peracetic acid
high killing activity and a broad spectrum against bacteria, spores, viruses, and fungi
their decomposition products are not toxic and do not injure the environment
Peroxygen compounds - hydrogen peroxide
- disinfection of respirators, soft contact lenses…
- 10–25% hydrogen peroxide are sporicidal
- Automated equipment using vaporized hydrogen peroxide or hydrogen peroxide mixed with formic acid is available for sterilizing endoscopes
- 3% solution of hydrogen peroxide is commonly used as a wound antiseptic
Peroxygen compounds Peracetic acid (CH3COOOH)
- hydrogen peroxide + acetic acid + sulfuric acid as a catalyst
- more active than hydrogen peroxide as a bactericidal and sporicidal agent
- An automated machine - developed for sterilization of medical, surgical, and dental instruments.
- hemodialyzers
- potent tumor promoter
Heavy metals
principally mercury and silver
rarely used as disinfectants
Heavy metals - mercury
Pro:
thimerosal (organomercury compound) 0.001–0.004% is still used safely as a preservative of vaccines, antitoxins, and immune sera
Con:
- environmental hazard
- some pathogenic bacteria have developed plasmid-mediated resistance
- Hypersensitivity (in up to 40% of the population)
Heavy metals - silver
Inorganic silver salts are strongly bactericidal
Silver nitrate 1:1000, has been most commonly used - gonococcal ophthalmitis in newborns (Credé’sprophylaxis)
Silver sulfadiazine used to suppress bacterial growth in burn wounds
*Octenidine
cationic antiseptic
It is bactericidal against Gram-positive and Gram-negative bacteria as well as fungicide.
Octenidine may have a larger antibacterial activity spectrum than chlorhexidine, in particular towards Gram-negative bacteria.
A development of resistance to octenidine has not been reported.
No side effects of octenidine have been described.
Sterilisation
validated process used to render a product free of all forms of viable microorganisms.
Sterilants
Autoclaving for many year: pressurized steam at 120°C for 30 minutes
When autoclaving is not possible (lensed instruments, plastic and rubber) - ethylene oxide - 440–1200 mg/L at 45–60°C with 30–60% relative humidity
-Con: classified as a mutagen and carcinogen
Alternative sterilants now being used increasingly
- vapor phase hydrogen peroxide
- peracetic acid
- Ozone !
- gas plasma
- chlorine dioxide
- Formaldehyde
- propylene oxide
- UV-light
