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Evaluation of the efficiency of sterilization methods. Sterility indicators

  1. PHARMACEUTICAL MICROBIOLOGY (BP303T) Unit-Ii Part-3 Evaluation of the efficiency of sterilization methods. Sterility indicators Name: Mrs. Pooja Deepak Bhandare Assistant Professor G H RAISONI UNIVERSITY SCHOOL OF PHARMACY
  2. Content: •Evaluation of the efficiency of sterilization methods. •Sterility indicators 12/8/2022 Sample Footer Text 2
  3. Sterility criteria • Bioburden is normally defined as the number of bacteria living on a surface that has not been sterilized. • The term is most often used in the context of bioburden testing, also known as microbial limit testing, which is performed on pharmaceutical products and medical products for quality control purposes. • • Time and temperature relationship for steam sterilization to ensure that a large number of the most resistant pathogens would be killed.
  4. Sensitivity of microorganisms •Microorganisms shows resistance to heat, radiation and chemicals. • •The vegetative forms of bacteria and fungi are most sensitive. • •The thermophilic bacteria, smaller viruses and mould spores are killed at temperature between 70 to 90°C, while bacteria spores may be destroyed at 90 to 120°C temperatures.
  5. Death rate or Survivor curve • It is determined by assessing the reduction in the number of viable microorganisms resulting from contact with a given destructive force. • This can be represented graphically with a ‘survivor curve’ drawn from plot of the log of the fraction of survivor against the exposure time or dose.
  6. D- Value or Decimal reduction time • Time in minutes at any defined temperature to destroy 90% viable microorganisms is called D- value
  7. Z- value or Thermal reduction time • The slope of the TDT curve is defined as “Z” which is equal to the number of degrees on the temperature scale when the curve traverse one log cycle. • Z is the change in temperature necessary to cause a ten fold change in D-value. • The value of Z for C. botulinum is 10˚C • Every 10˚C change in temperature there is a ten fold change In its death rate. • B. subtilis has Z value of 6.5˚
  8. f- value • Used in the food industry, also called “Unit of Lethality” has been devised called as F- Value • This can be defined as the equivalent in minutes of 121˚C of all heat consider with respect to its capacity to destroy spores or vegetative cell of a particular organisms • The F value for a process is the number of minutes required to kill a known population of microorganisms in a given food under specified conditions. • This value is also used to calculate the probable number of bacterias remaining after the process in food.
  9. Q10 Value or Temperature Coefficient • It is defined as the increase in rate of reaction or killing rate of a sterilization process brought after increasing the temp. by 10°C.
  10. InactivationFactor: • It is the degree to which the viable population of organisms is reduced by applying a sterilization process. • It is obtained by dividing the initial viable count by final viable count. • Inactivation factor (IF) = 10 t/D • Where, t = exposure time in minutes , • D = Decimal reduction time for the same temperature and conditions.
  11. STERILITY INDICATORS • Changing appearances in colour or pattern, the sterilization indicators visually show if cleaning conditions are passing or procedures have been completed. • • Eliminating any confusion or possibility instruments will not be sterile, indicators are used routinely in clinical and research environments where contamination elimination is crucial. • With the temperature resistance required to endure the purification, the sterilization indicators are available in different forms such as tapes, ampoules, and sticks. • Monitoring of sterilization process can be achieved by the use of 1. Physical Indicators 2. Chemical Indicators 3. Biological Indicators
  12. 1. Physical Indicators •Monitoring physical indicators involves observing the gauges or displays on the sterilizer and recording the time, temperature, and pressure associated with each sterilization cycle for each load. • Some sterilizers have recording devices that print out these parameters. •Correct readings do not guaranty sterilization, but incorrect readings can be the first indication of a problem with the sterilization cycle and suggest the load may not be sterile.
  13. i) Moist heat Indicator: A Master Process Record (MPR) is prepared as part of the validation procedure for a particular autoclave The MPR should be checked at annual intervals and whenever significant changes occur in the BPR(Batch Production Records)when compared with the MPR. Microprocessor-controlled sterilization cycles are now a part of modern autoclaves. ii) Dry heat: in dry sterilization processes, a temperature record chart is made of each sterilization cycle and is compared against a master temperature record. iii) Radio sterilization: A plastic dosimeter gives an accurate measure of the radiation does absorbed and is considered to be the best technique currently available for the radio sterilization process.
  14. iv) Gaseous methods: For gaseous sterilization procedures, elevated temperatures are monitored for each sterilization cycle by temperature probes and routine leak test are performed to ensure gas-tight seals. Gas concentration is measured independently of pressure rise, often by reference to the weight of gas used. Pressure and humidity measurements are record. v) Filtration: Bubble point pressure test is a technique employed for determining the pore size of filters and may also be used to check the integrity of certain types of filter devices immediately after use. The principle of the is that the filter is soaked in an appropriate fluid and pressure is applied to the filter. The pressure difference when the first bubble of air breaks away from the filter is equivalent to the maximum pore size. When the air pressure is further increased slowly, there is general eruption of bubbles over the entire surface. The pressure diffference is equivalent to the mean pore size.
  15. 2.CHEMICAL INDICATORS •Chemical indicators use sensitive chemicals to assess critical variables (e.g., time, temperature, or steam saturation) during a sterilization cycle. •They are applied either to the outside or placed on the inside of each instrument unit (e.g., packs, peel pouches, containers, etc… •They do not prove that sterilization has been achieved, but they can provide an early indication of a problem and where in the sterilization process the problem might exist.
  16. I) Browne’s tubes: Most commonly used chemical indicator for heat process Contains small sealed coloured tubes having a reaction mixture and an indicator Expose to high temperature resulting in the change of colour of the indicators.(Red to green) II) WITTNESS TUBES • Consist of single crystalline substances of known melting point contained in glass tubes Ex: Sulphur(115°C), Succinic anhydride(120°C), Benzoic acid(121°C), etc. • A dye may be included to show more clearly that the crystals have melted. • Indicates that a certain temperature has been reached.
  17. III)Heat Sensitive Tape: • It is an adhesive tape used in autoclaving to indicate a specific temperature. • Autoclave tape works by changing color after exposure to temperatures commonly used in sterilization processes, typically 121°C in a steam autoclave. • Small strips of the tape are applied to the items before they are placed into the autoclave. • The tape is similar to masking tape but slightly more adhesive, to allow it to adhere under the hot, moist conditions of the autoclave. • One such tape has diagonal markings containing an ink which changes colour (usually beige to black) upon heating.
  18. IV) Royce Sachet: • It's a chemical indicator used for “Ethylene Oxide Sterilization”. • Its a polyethylene sachet containing magnesium chloride and bromophenol blue indicator. • Ethylene oxide penetrates polyethylene bags and reacts with the contents of the sachet. • At a given concentration - time exposure the color of the mixture changes from yellow to purple due to formation of “Ethylene chlorohydrin”. V) Chemical Dosimeter: • It is the best technique available to measure radiation dose absorbed during sterilization by radiation. • The radio sensitive materials are impregnated in a plastic container and changes color from yellow to red on exposure to the radiations.
  19. 3.BIOLOGICAL INDICATORS •Biological indicators (BIs), or spore tests, assess directly the killing of known highly resistant, non pathogenic bacterial spores. •Geobacillus stearothermophilus (G. stearothermophilus) spores test steam and unsaturated chemical vapor sterilizers. •Bacillus atrophaeus (B. atrophaeus) spores test dry heat sterilizers. •Bacterial spores in the test products are more resistant and are present in greater numbers than common microbial contaminants found on patient-care items.
  20. Sterilization Process Species Used Autoclaving at 121°C Bacillus stearothermophilus Clostridium sporogenes Dry heat at 160°C Bacillus subtilis var.niger Ethylene Oxide Bacillus subtilis var.niger Ionizing radiations Bacillus pumilus Membrane filter (0.45 micrometer) Serratia marcescens Membrane filter (0.22 micrometer) Pseudomonas diminuta