34
Dr Shahla Latif

[Micro] sterilization

Embed Size (px)

Citation preview

Page 1: [Micro] sterilization

Dr Shahla Latif

Page 2: [Micro] sterilization

1866 J Lister suggested antiseptic surgery.

Putrefaction is caused by microbes Wound sepsis is a form of putrefaction Wound sepsis is caused by microbes

Page 3: [Micro] sterilization

STERILIZATION

GERMICIDE/DISINFECTANT

ANTISEPTIC

Page 4: [Micro] sterilization
Page 5: [Micro] sterilization

Nature of heat

Temperature and time

Number of microorganisms

Nature of microorganism

Type of material

Presence of organic material

Page 6: [Micro] sterilization

Dry heat acts by protein denaturation, oxidative damage and toxic effects of elevated levels of electrolytes.

Moist heat acts by coagulation and denaturation

of proteins.

Thermal death time is the minimum time required to kill a suspension of organisms at a predetermined temperature in a specified environment.

Page 7: [Micro] sterilization

Hold the inoculating loop inside an alcohol burner or bunsen burner flame for a few seconds to bring it to redness and then

remove for 15-30 seconds to cool.

Page 8: [Micro] sterilization

Uses glassware, metal

instruments, oils, powder

Temperature 160o/2hours 170o/1hour

Page 9: [Micro] sterilization

Physical: Temperature chart recorder and thermocouple.

Chemical: Browne’s tube No.3 (green spot, color changes from red to green)

Biological: Bacillus subtilis (niger) or 106 spores of Clostridium tetani on paper strips are placed inside envelopes and then placed inside the hot air oven

Page 10: [Micro] sterilization

Incineration >500o Vaporizes organic material on nonflammable surfaces but may destroy many substances in the process

Page 11: [Micro] sterilization

It is employed in food and dairy industry.

Holder method (heated at 63oC for 30 minutes) Flash method (heated at 72oC for 15 seconds) followed by

quickly cooling to 13oC.

Ultra-High Temperature (UHT), 140oC for 1-2 sec and 149oC for 0.5 sec.

Purpose: TO eliminate pathogens like Salmonella, Mycobacteria, Streptococci, Staphylococci and Brucella, however Coxiella may survive pasteurization.

Efficacy is tested by phosphatase test and methylene blue test.

Page 12: [Micro] sterilization

100o for 30 minutes (more time at high altitude). Kills everything except some endospores.

For the purposes of purifying drinking water, 100o for five minutes is a "standard" in the mountains" though there have been some reports that Giardia cysts can survive this process.

When absolute sterility is not required, certain metal articles and glasswares can be disinfected by placing them in boiling water for 10-20 minutes. The lid of the boiler must not be opened during the period.

Page 13: [Micro] sterilization

Instead of keeping the articles in boiling water, they are subjected to free steam at 100oC exposed for a period of 90 minutes.

Media such as TCBS, DCA and selenite broth are sterilized by steaming.

tyndallisation: Sugar and gelatin in medium may get decomposed on autoclaving, hence they are exposed to free steaming for 20 minutes for three successive days.

Page 14: [Micro] sterilization

15 lbs 121oC. 15 minutes

prions 135oC or 121oC for at least one hour are recommended.

Advantages of steam: It has more penetrative power than dry air, it moistens the spores (moisture is essential for coagulation of proteins), condensation of steam on cooler surface releases latent heat, condensation of steam draws in fresh steam.

Page 15: [Micro] sterilization

Heating Period Sterilization

Period Safety Period (½)

Page 16: [Micro] sterilization
Page 17: [Micro] sterilization

USES Culture media, dressings, linen.

PRECAUTIONS Articles should not be tightly packed.

The autoclave must not be overloaded.

Air discharge must be complete and there should not be any residual air trapped inside.

Caps of bottles and flasks should not be tight.

Autoclave must not be opened until the pressure has fallen or else the contents will boil over.

Bottles must not be overfilled.

Page 18: [Micro] sterilization

STERILITY STERILITY ASSURANCEASSURANCESTERILITY STERILITY

ASSURANCEASSURANCE

MECHANICALMECHANICAL

CHEMICALCHEMICAL

BIOLOGICALBIOLOGICAL

COMBINED COMBINED RESULTSRESULTS

Page 19: [Micro] sterilization

Physical method includes automatic process control, thermocouple and temperature chart recorder.

Chemical method Browne’s tube No.1 (black spot)

and succinic acid (whose melting point is 121oC) and

Bowie Dick tape. Bowie Dick tape is applied to articles being autoclaved. If the process has been satisfactory, dark brown stripes will appear across the tape.

Biological method includes a paper strip containing 106 spores of Bacillus stearothermophilus. Culture 55C/5days

Page 20: [Micro] sterilization

CHEMICAL INDICATOR BIOLOGICAL INDICATOR

Page 21: [Micro] sterilization

“It takes more time to kill a large

population of bacteria than it does to kill

a small population,

because only a fraction of organisms

die during a given time interval.

Page 22: [Micro] sterilization

Decimal Reduction Time (D value) = the time it takes to kill 90% of a bacterial population (1 log reduction) under specific conditions.

Critical Items penetrate into body tissues.

Semicritical Items come into contact with but don’t penetrate mucous membranes.

Non-Critical Items come into contact only with unbroken skin.

Page 23: [Micro] sterilization

Filtration antibiotics, injectable drugs, amino acids, vitamins.

Portable units can be used in the field for water purification and industrial units can be used to "pasteurize" beverages.

Essentially, solutions or gases are passed through a filter of sufficient pore diameter (generally 0.22 micron) to remove the smallest known bacterial cells.

FILTER

Page 24: [Micro] sterilization

1884

1891Germany

Page 25: [Micro] sterilization

Earthware candle jar filters:

Berkefield:V(coarse), W(fine),N(middle)

Chamberland: L1 to L13(finest)

Asbestos (Sietz) filters: HP/PYR (for removal of pyrogens),

HP/EKS (for absolute sterility) and

HP/EK (for claryfying). used only once

Sinterd glass filters: 00 to 5/3,washed in running H2O

in reverse direction and cleaned with warm concentrated H2SO4 and sterilized by autoclaving

Cellulose membrane filters:

Cellulose nitrate (old) Cellulose acetate (new)pore diameter 0.015to

12um(0.22um) sterilized by autoclaving.

Page 26: [Micro] sterilization
Page 27: [Micro] sterilization

Air Filters: Air can be filtered using HEPA (High Efficiency Particle Air) filters. They are usually used in biological safety cabinets

Page 28: [Micro] sterilization

Light energy is inversely related to wavelength

Absorption of light: Absorption capacity Time of exposure Intensity of light

Page 29: [Micro] sterilization

U/V RADIATION: (240-280nm) Low energy Low penetration power Produces dimers

Ionizing radiation: X-ray, γ rays High energy High penetration power Produces breaks

Page 30: [Micro] sterilization

Ultraviolet lamps (mercury vapor lamp)

germicidal wavelengths 240-280nm optimum 260nm(absorption max. of DNA) causes pyrimidine dimers thereby inhibiting DNA replication

UV rays don’t kill spores

Used to disinfect: hospital wards operation theatres virus laboratories corridors

Supplement to other sterilization techniques, since microorganisms can be shielded from ultraviolet light in fissures, cracks and shaded areas & it doesn't penetrate glass, paper or plastic.

Page 31: [Micro] sterilization

Products of radioactive decay (alpha, beta & gamma rays)

Or produced in X-ray machine by particle bombardment or nuclear reactors.

Used in sterilization are electromagnetic Xrays & gamma rays and particulate cathode rays (artificially accelerated electrons)

Page 32: [Micro] sterilization

Gamma radiation emitted from cobalt-60, caesium-137 are similar in many ways to microwaves and x-rays. Gamma rays delivered during sterilization break chemical bonds by interacting with the electrons of atomic constituents. Gamma rays are highly effective in killing microorganisms and do not leave residues or have sufficient energy to impart radioactivity.

Electron beam (e-beam) radiation is similar to gamma radiation as it alters various chemical and molecular bonds on contact. Beams produced for e-beam sterilization are concentrated, highly-charged streams of electrons generated by the acceleration and conversion of electricity.

Used for sterilization of items ranging from syringes to cardiothoracic devices. Catgut & nylon sutures, disposable surgical & medical supplies

Page 33: [Micro] sterilization

Direct Damage

Indirect Damage via hydrolysis OH., H H2O→H2O(+)+e‾

H2O(+) +H2O→H3O(+) + OH.(oxidizing agent)

e‾ + H2O→ OH‾+H.(reducing agent)

Page 34: [Micro] sterilization