Dr Shahla Latif
1866 J Lister suggested antiseptic surgery.
Putrefaction is caused by microbes Wound sepsis is a form of putrefaction Wound sepsis is caused by microbes
STERILIZATION
GERMICIDE/DISINFECTANT
ANTISEPTIC
Nature of heat
Temperature and time
Number of microorganisms
Nature of microorganism
Type of material
Presence of organic material
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.
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.
Uses glassware, metal
instruments, oils, powder
Temperature 160o/2hours 170o/1hour
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
Incineration >500o Vaporizes organic material on nonflammable surfaces but may destroy many substances in the process
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.
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.
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.
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.
Heating Period Sterilization
Period Safety Period (½)
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.
STERILITY STERILITY ASSURANCEASSURANCESTERILITY STERILITY
ASSURANCEASSURANCE
MECHANICALMECHANICAL
CHEMICALCHEMICAL
BIOLOGICALBIOLOGICAL
COMBINED COMBINED RESULTSRESULTS
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
CHEMICAL INDICATOR BIOLOGICAL INDICATOR
“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.
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.
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
1884
1891Germany
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.
Air Filters: Air can be filtered using HEPA (High Efficiency Particle Air) filters. They are usually used in biological safety cabinets
Light energy is inversely related to wavelength
Absorption of light: Absorption capacity Time of exposure Intensity of light
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
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.
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)
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
Direct Damage
Indirect Damage via hydrolysis OH., H H2O→H2O(+)+e‾
H2O(+) +H2O→H3O(+) + OH.(oxidizing agent)
e‾ + H2O→ OH‾+H.(reducing agent)
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