Sterilization and Disinfection

1. Sterilization and Disinfection S.K.Madhup DH,KUH

2. MOIST HEAT • More rapid and effective method • Heat in the presence of water • Moisture of steam reduce the longer exposure time • It can be employed in different ways • e.g. Temp. 100°C • Above100°C • Below100°C • Denaturation and coagulation of proteins.

3. MOIST HEAT • Temp below 100 c • Pasteurisation of milk Two methods The holder method -63 c for 30 min The flash process - 72 c for 15-20 sec followed by cooling quickly to 13 c By this processes all nonsporing pathogens such as Mycobacterium,Brucella and Salmonella are destroyed. Coxiella burnetii is relative heat resistant and may survive the holder method. Vaccine baths- vaccines of nonsporing bacteria are heat inactivated in special vaccine baths at 60 c fot 60 min. Serum and other body fluid containing coagulable proteins can be sterilized by heating for 60 min at 56 c in a water bath

4. Inspissator -30 min at 80-85 c for three successive day. Lowenstein-Jensen and Loeffler’s serum slope A temp of 80 c for 5-10 min destroys the vegetative forms of all bacteria , yeast and moulds. • Temp at 100 c Boiling-Vegetative bacteria are killed almost immediately at90-100 c , but sporing required prolonged periods of boiling . Sterilisation may be promoted by the addition of 2% sodium bicarbonated to the water

5. Steam at atmospheric pressure(100 c) Tyndallisation or intermittent sterilisation. • Steam under pressure.- Autoclave Principle- is that water boils when its vapour pressure equals that of the surrounding atmos. Hence when pressure inside a closed vessel increases , the temp at which water boils also increase. Saturated steam has penetrative power.when steam comes into contact with a cooler surface it condenses to water and give up its latent heat to that surface. The large reduction in volume sucks in more steam to the area and the process continues till the temp of that surface is raised to that of the steam . The condensed water ensures moist condition for killing the microbes present. time and temp- 121 c at 15lbs for 20 min • Type of steam sterilisers lab autoclave Hospital dressing sterilisers Bowel and instrument sterilisers Rapid cooling sterilisers

6. Types of steam sterilizers • Gravity displacement sterilizer • Two shells that form a jacket and chamber Steam fills the jacket. Steam enters the chamber after door closes Air goes to bottom and steam floats on top (air is heavier than steam ) Sterilizing period starts when thermometer reaches the desired temperature.

9. Types of steam sterilizers • PREVACUUM STERILIZER • Air is evacuated from chamber before sterilizing steam is admitted • Vaccum is achieved by pump • Instantaneously penetrates packages • Maximum capacity of sterilizer used • 132°C x 27 psi x 15min.

10. Types of steam sterilizers • FLASH STERILIZATON • May have either Gravity displacement or prevaccum cycle. • 27psi x 132°C x 3min. • Used in urgent emergency operation • Items which are implanted permanently are not implanted until biological monitoring.

11. Advantages of steam sterilization • Easiest • Safest • Surest • Fastest method • Less expensive • Automatic control • Steam leaves no harmful effect.

12. Disadvantages • Precautions in • Preparing, packaging, loading, operating. • Items need • to be clean ,free of grease, oil and not sensitive to heat. • must have direct contact with all areas. • Timing of cycle adjusted for size of load and type of material.

13. USES OF MOIST STERILIZATION • Metal instruments • Rubber gloves • Respirator parts • Surgical dressing • Parenteral products • Nonparenteral fluid • Ophthalmic solutions.

14. Precautions • Removal of air from load • Thus complete mixing of steam and elimination of cold spots in the autoclave. • Ideally 100% steam saturated steam is required. • The quality of steam is important • “Weight of dry steam in a mixture of dry saturated steam and water in a system.”

15. Methods & Principles (Cont.) Other autoclaves: • High security autoclaves • For pathogens of containment level 3 & 4 • Steam outlet filter fitted & very high • Double ended • Low temperature steam sterilizer (Only disinfection) • 730C for 10 minutes • Multi-pulsing vacuum air removal • Insertion of steam at 263 mm of Hg

16. Methods & Principles (Cont.) • Gas sterilization: • Exposure to low temperature steam and formaldehyde (LTSF) • Steam at 263 mm of Hg (730C) • + • Large volumes of formaldehyde gas

18. Filtration • Sintered glass filters : • low adsorbing capacity • brittle and expensive • Membrane filters : • cellulose esters/ nitrocellulose • 0.22 µm size most widely • Candle • Asbestos

19. High Efficiency Particulate Air (HEPA) Filters 3-Stage Filtration System • Carbon prefilter removes lint and odors before they enter true HEPA Filter. • True HEPA Filter is 99.97% efficient . • Filter helps remove volatile organic compounds such as formaldehyde and toluene.

20. System: • Carbon

21. Radiation: • Non ionizing • IR • M/A: heating effect • UV • M/A: nucleotide dimers • Ionizing • Gamma Rays, high energy electrons. • M/A- DNA breakdown by highly reactive molecules.

22. UV Radiation: • Bactericidal effect at 240-280 nm. • Less penetrating ability.

23. Radiation Sensitivities

24. Use of radiation sterilization

25. Application • Non ionizing • IR • syringe, catheters. • UV use in • entry ways, operation theatre. • Ionization • plastics, syringes, catheters, metal foils, oils. packaging devices.

26. Chemical agents: • Used only when heat, radiation can not employed • Less efficient than physical agents. • Toxicity

27. ALDEHYDES • Formaldehyde • used in liquid and vapour state • In aqueous solution containing 34-38% w/w of formaldehyde. • Bactericidal, sporicidal and lethal effect on viruses. • Preserve anatomical specimens. • Formaldehyde gas is used for sterilizing instruments and heat sensitive catheters and laboratories, fumigating wards.

28. Glutaraldehyde: • (Pentane -1,5 dialdehyde)C5H8O2. • It reacts with enzymes and proteins, but only slightly with nucleic acids. • In practice 2% glutaraldehyde required. • To treat corrugated rubber, anesthetic tubes and face masks • plastic endotracheal tubes • metal instruments and polythene tubing. • Sterilant at 10 hrs and high disinfectant at 25 to 30 min.

29. Peracetic acid • Acetic acid plus an extra oxygen atom that reacts with cellular components to cause cell death. • 0.2% peracetic acid solution • 20 to 30 min and heated 122 °C to131°C. • It passes through the self processing chamber.

30. Ethylene oxide: • Highly inflammable and con. > 3% highly explosive. • By mixing with inert gas CO2, Nitrogen to a con. of 10% its explosive tendency eliminated. • Its action due to its alkylating protein molecules. • It also reacts with DNA and RNA. • EO Chambers • automatically controlled gas concentration, temp, humidity, time.

31. Ethylene oxide: • Depends upon four factors • Concentration of EO gas • highly inflamable so diluted by CFC-12 / HCFC-124/ CO2 • Temperature • 29-63°c operate. • Humidity • 30-80%maintained. • Time-depends on concentration and temperature of gas.

32. Advantages of EO Gas • Plastics with low melting points. • Noncorrosive • Permeates all porous material. • It is not recommended for oils, liquid,powder, glass solutions with rubber stopper. • No film on item • Used for sterilizing Heart-lung machines, respirators sutures, dental equipments, books, clothing.

33. Disadvantages of EO • Complicated, long, slow process. • Expensive equipment. • Rubber, polyethylene,silicone require aeration period. • Toxic by-products can be formed in the presence of moisture during exposure of plastics. • Irritating to mucous membranes. • Long term exposure causing leukemia. • Unsuitable for fumigating rooms because of its explosive nature.

34. Hydrogen peroxide plasma sterilization • Plasma • fourth state of matter. • Hydrogen peroxide can be activated to create a reactive plasma. • Cloud of plasma consists of • ions, electrons, neutral atomic particles. • It interact with plasma membranes, enzymes, nucleic acids of microorganisms. • Sporicidal at a low concentration and temperature.

35. Advantages • Use for metal and nonmetal devices at low temperatures. • Process is dry, nontoxic. • By-products of oxygen and water vapor are safely evacuated. • Aeration is not necessary. • heat-sensitive items sterilized.

36. Disadvantages • Metal trays block radiofrequency waves. • Noncompatible with cellulose. • Nylon becomes brittles.

37. Methods Of Monitoring • Physical • Record time, temperature, pressure, gas concentration. • Chemical indicator • These indicator classes are • a. External indicator / process indicator. • b. Air removal indicator (Bowie-dick ) • c. Integrator-respond to two or more parameter. • d. Correlate with biological indicator • e. Steam penetration indicator

38. MONITORING(Contd.) • Biological indicator • Calibration of microorganisms in or on a carrier put up in a package that maintains the integrity of inoculated carrier. • Three type • Paper strips inoculated with bacterial spores. • Self contained-spores enclosed in carrier state. • Enzyme based-most rapid.

40. HOSPITAL PRACTICE 1.Infection control policy and program 2.Rationalization of patient admission 3.Disinfection and sterilization use 4.Disposal of Hospital waste 5.Training of Health care provider.

42. CENTRAL STERILE SUPPLY • Collecting and receiving patient unusable items, instruments. • Key element of CSS infection control, quality assurance, occupational safety and health. • Area of CSS- • Receiving, decontamination, cleaning, • Decontamination. • Personal support area • sterilization area • packaging area • sterile storage area • administrative area

43. Cleaning removal of all adherent visible soil from the surfaces, crevices, joints, lumina of instruments. done by manual ultrasonic, automated . Decontamination physical or chemical process that renders a potentially contaminated object inanimated and safe for further handling. done by washer sterilizer or washer decontaminator reduction of bioburden. CENTRAL STERILE SUPPLY

44. CENTRAL STERILE SUPPLY • Packaging • Intact wrapper impervious to extraneous microbes, moisture, dust. • Paper , textile , pouch packs , rigid container • Allow suitable printing. • Provide evidence of tampering. • Compatible with sterilization • Should allow adequate air removal, steam penetration, drying. • Allow adequate penetration, release of gaseous sterilant.

45. Risk acquiring HIV, HBV, HCV : by blood, blood products, contaminated medical equipment. • HIV: Percutaneous exposure: 0.05-0.4% Mucocutaneous exposure: 0.006-0.05% • HBV: Percutaneous exposure : 9-30% • HCV: Percutaneous exposure : 3-10% • Patient specimen • Autoclaving at 121°c for 20 min. • Dry heat - 170°c for 1hr. • Boiling for 20-30 min. • Glutaraldehyde 2% for 30 min. • Formalin 3-4%