Sterilization and Disinfection

autoclave

(15 lb/sq inch pressure for 15-20 min at 121 degrees) - sterilizes with moisture, microorganism are destroyed at lower temp than in dry heat - method of choice when product can withstand such treatment since its fast, least toxic, cheap, can be performed on large spectrum of instruments - sterilizing indicators= kilit ampule- spores of bacillus stearothermophilus + fermentable sugar with pH indicator

alcohol

* 60-90% - mode of action- disruption of cellular membrane, solubilization of lipids, and denaturation of proteins by acting directly on S-H functional groups - they evaporate rapidly, which makes extended contact times difficult to achieve unless the items are immersed - used to clean instruments and wipe down areas but are ineffective against spore-forming bacteria - alcohols are generally regarded as being non-corrosive EX. ethyl and isopropyl alcohol

Ethylene oxide

* C2H4O - sterilizes via its action as a powerful alkylating agent -low temp. sterilization = use for heat-labile materials and delicate instruments - requires hermetic oven for admission of gas + 20-50% humidity at 30-60 degrees - C2H4O converts to CO2

Glutaraldehyde

*2% - sterilizing agent against bacteria, spores and viruses - often requires MANy hours of exposure - 10x more effective than formaldehyde and less toxic - toxic and causes skin sensitization - EX. cidex- a commercially prepared glutaraldegyde disinfectant is used routinely for cold surface sterilization of clinical instruments

Formaldehyde

*5% - broad-spectrum biocidal sterilizing activity - surface and space decontamination - mode of action= alkylation of carboxyl, hydroxyl and sulfhydryl groups on proteins and the ring nitrogen atoms of purine bases - drawbacks- reduction in efficacy at refrigeration temperature, pungent, irritating odor, considered to be a carcinogen -EX. sterac

Surface active agents

*ionic detergents - odorless, colorless, nonirritating, and deodorizing that have detergent action Mode of action: through inactivation of energy producing enzymes, denaturation of essential cell proteins, and disruption of cell membrane - used in water baths, incubators, and other applications where halide or phenolic residues are not desired - not suitable for terminal disinfection since ineffective against viruses, spores and mycobacterium -EX. zephirin, CDQ, A-33, End-Bac, Hi-Tor, Mikro-Quat 1. cationic agents (quaternary ammonium compounds) - zephiran 2. anionic agents- soaps

Filtration

- <0.22 micrometer pore -removes microorganisms from liquids that would be destroyed by heat (enzymes, vaccines, antibiotics) -berkfield, seitz, millipore & sintered glass

Hot air (dry heat) sterilization

-160 degrees for 1-4 hours - used on materials that would be damaged by moist heat (gauzes, dressings, powders)

Halogens

-principle ones used in disinfection or sterilization are iodine and chlorine - uses chlorine = good as disinfectant if bleach is diluted to 1:10. must be made fresh daily iodine= good as disinfectant and antiseptic method of action- oxidizes microbial proteins examples- chlorine (household bleach = 5.25%, Na-hypochlorite, Chloramine T, Purex) & iodine (wescodyne, betadyne, povidone-iodine)

Radiation

-used on materials that would be destroyed by heat (petri dishes, gloves, syringes) *Ultraviolet- thymine dimers- poor penetration (photolyase involves repair. lack of this enzyme causes xeroderma pigmentosum) - efficiency proportional to the absorption by nuclear protein *Ionizing (beta rays, gamme rays, x-rays) - breaks in DNA backbone

Chemical sterilization/disinfection methods

1. Ethylene oxide 2. Aldehydes - glutaraldehyde - formaldehyde 3. alcohol 4. halogens 5. heavy metals -mercury -silver 6. phenolic 7. surface active agents

What is the rule of thumb

1. autoclave if possible 2. gas if material is liquid/moisture sensitive and heat sensitive (electronic equipment or paper)

mode of action of alcohol

1. disrupt cell membrane 2. solubilization of lipids 3. denaturation of proteins by acting directly on S-H functional groups

What type of sterilization used for: 1. guazes 2. petri dish 3. powders 4. syringe 5. vaccines 6. gloves 7. enzymes 8. dressings 9. antibiotics

1. hot air (dry heat) 2. radiation 3. hot air (dry heat) 4. radiation 5. filtration 6. radiation 7. filtration 8. hot air (dry heat) 9. filtration

Physical methods of sterilization

1. incineration 2. ultrasonification 3. filtration 4. radiation 5. hot air (dry heat) sterilization 6. steam and hot water 7. autoclave

Steam and hot water (3 types)

1. instrument sterilizer 2. harvey vapor sterilizer/chemiclave 3. arnold sterilizer

Methods of sterility monitoring

1. mechanical - monitor conditions (cycle length, pressure, temp) - does NOT prove sterilization 2. chemical - utilize external and internal chemical indicators (ex. autoclave indicator tape or colorimetric ampules) to assess physical conditions (ex. temperature NOT time) - does NOT prove sterilization 3. Biological -most accepted method for monitoring sterilization process - directly assess killing of known highly resistant microorganisms ONCE per week MINIMUM

What can disinfection be accomplished by?

1. paraformaledgyde, aldehyde, and hydrogen peroxide with per acetic acid sterilants with short contact times 2. all others mentioned: halogens (chlorine and iodophors), phenolics, quaternary ammonium compounds

Why bother with sound principles and methods of infection control

1. protection from infectious hazards 2. impacts on business operations of clinical practice

What can sterilization be accomplished by?

1. steam sterilization (autoclave 120 for 20 min) 2. dry-heat sterilization (160 for 1-2 hours) 3. ethylene oxide 4. ionizing radiation 5. paraformaldhyde, aldehyde, and hydrogen peroxide with per acetic acid sterilants with appropriately long contact times

Biological sterilization monitering sterilization method and marker organism for each

1. steam sterilization - B. stearothermophyilus 2. Dry-heat sterilization and ethylene oxide- B. subtitles 3. ionizing radiation sterilization - B. Pumilus

Disadvantages of ethylene oxide

1. toxicity - eye and skin irritations - nausea, vomit, respiratory tract disorder - depression - intermittent high exposures = neurological and reproductive cancers 2. explosive 3. no liquid sterilization 4. ex. carboxide, cryoxide, steroxide 5. beta-propiolactone is similar

The effectiveness of autoclaving is best determined by: A) Culturing bacterial spores B) Culturing the water reservoir C) Thermocouples (temperature measuring device) D) Indicators that change color at elevated temperature

A

The spores of Bacillus anthracis are destroyed by: A) Refridgerating (-7oC for 48 hours) B) Autoclaving (121oC for 20 minutes) C) Pasteurizing (61.7oC for 30 minutes) D) Immersing in boiling water (100oC for 10 minutes) E) Placing in a hot air oven (121oC for 20 minutes)

B

ultrasonification

Breaking intermolecular interactions - generally used to only clean materials, NOT use to sterilize, only cleans through cavitation

Which of the following is MOST resistant to sterilizing conditions A) Oral Yeast B) Hepatitis B virus C) Bacterial endospores D) Mycobacterium tuberculosis E) Human Immunodeficiency Virus

C

Examples of halogens

Chlorine - household bleach = 5.25% - Na-hypochloite -Chloramine T -Purex Iodine -wescodyne -betadyne -povidone-iodine

When to use halogens

Chlorine- disinfectant if bleach is diluted to 1:10 - must be made fresh daily Iodine- disinfectant and antiseptic

Dry heat sterilization of dental instruments requires A) 3 minutes at 270oF (132oC) B) 20 minutes at 250oF (121oC) C) 30 minutes at 320oF (160oC) D) 60 minutes at 340oF (171oC) E) 6 hours at 100oF (38oC)

D

In a dry heat oven, which of the following temperatures is sufficient for achieving sterilization in 1-2 hours A) 81oC B) 100oC C) 121oC D) 160oC

D

Sterilization of surgical instruments that are sensitive to heat can be accomplished by using: A) phenol B) an autoclave C) ethyl alcohol D) ethylene oxide

D

Antiseptics differ from disinfectants in that antiseptics: A) sterilize B) kill pathogens C) are bactericidal only D) are bacteriostatic only E) are applied to living tissue

E

Which of the following disinfectants is effective against herpes simplex viruses but not rhinoviruses A) Phenolics B) Iodophores C) Glutaraldehydes D) Sodium hypochlorite E) 70% isopropyl alcohol

E

Which of the following represents the BEST way to verify heat sterilization A) Using a chemical monitor B) Recording sterilizer pressure C) Recording duration of exposure D) Recording sterilizer pressure E) Testing with biological indicator

E

When is filtration used? when is radiation used?

Filtration- used on liquids that would be destroyed by heat (vaccines, antibiotics, enzymes) Radiation- used on materials that would be destroyed by heat (syringes, gloves, petri dishes)

Mercury

Inorganic mercury salts (ex. mercury chloride) - not used today Organic mercury compounds (metaphen, merthioalte, mercurochrome)

How can filtration be advantageous?

Pore size allows to allow viruses, but not bacteria to pass

Silver

Silver nitrate (1-2%) to prevent gonococcal infection in eyes of newborns - nanosilver

How does UV light and ionizing light destroy cells

UV- thymine dimers causes poor penetration ionizing (beta, gamme, xray)- breaks in DNA backbone

sanitization

a cleaning process which REDUCES pathogen levels to produce a healthy clean environment

Harvey Vapor sterilizer/chemiclave

alcohol plus formaldehyde under pressure

mode of action of formaldehyde

alkylation of carboxyl, sulhydryl and hydroxyl groups on proteins and the ring nitrogen on purine bases

Phenols

carbolic acid derivatives - disinfectant that acts through MEMBRANE damage - good against enveloped viruses, rickettsiae, fungi, and vegetative bacteria - retain more activity in the presence of organic material than any other disinfectant Cresols, hexachlorophene, alkyl-a and chloro derivatives and biphenyls are more active EX: lysol, pine-sol, amply, O-syl, tergisyl, vespene, L-Phase, expose, Hil-Phene, Matar, Mikro-Bac

example of ethylene oxide

carboxide, cryoxide, steroxide - beta-propiolactone is similar

Example of glutaraldhyde

cidex

How is glutaraldehyde used in dental setting

cidex- commercially prepared disinfectant used routinely for cold surface sterilization of clinical instruments

disadvantages of alcohol and advantages

dis - evaporate rapidly- extended contact times are difficult unless it is immersed - ineffective against spore-forming bacteria adv- non-corrosive

What do phenols work against

enveloped viruses, rickettsiae, fungi and vegetative bacteria

What is involved in UV light damage repair and what does this cause in humans that lack this enzyme

enzyme- photolyase involves repair in thymine dimers causes xeroderma pigmentosum if lacing photolyase

incineration

for disposable wastes (combustion of organic substances in waste products) - produces ash, gas heat

arnold sterilizer

fractional sterilizer (tyndallization)

When would you use ethylene oxide

heat labile material and delicate instruments

mode of action of surface active agents

inactivation of energy producing enzymes, denature essential cell proteins, and disruption of cell membrane

sterilization

inactivation or elimination of ALL viable organism and their spores

disadvantages of formaldehyde

lower efficacy at refrigeration temps, pungent, irritating odor, carcinogen

what type of microbes are more resistant to disinfection and which are less resistant *

more resistant- bacterial spores, mycobacteria, hydrophilic viruses, vegetative bacteria, lipophilic viruses (least resistant)

disadvantages of surface active agents

not suitable for terminal disinfection since they're ineffective against viruses, spores and mycobacteria

method of action of halogens

oxidize microbial proteins

disinfection

process of removing or killing MOST microorganisms on or in a material

Method of action of heavy metals

protein sulfhydrl groups and disruption of enzyme function

disadvantages of glutaraldehyde

requires many hours of exposure -toxic and causes skin sensitization (but less toxic than formaldehyde)

Instrument sterilizer

sodium carbonate and detergents

Example of formaldehyde

sterac

germicide

substance that kills vegetative bacteria and SOME spores

disinfectant

substance used on non-living objects to render them non-infectious; kills vegetative bacteria (endospores reactivate themselves in favorable conditions- bacillus and clostridium), fungi, viruses but NO spores

antiseptic

substance used to prevent multiplication of microorganism when applied to living systems. an antiseptic is BACTERIOSTATIC in action but necessarily bactericidal

Asepsis

the state of being free of microorganisms

Mode of action of phenols

through MEMBRANE damage

When to use surface active agents

water baths, incubators, other appliances where halide or phenolic residues are not desired