Autoclave sterilization, Exams of Biotechnology

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ASSIGNMENT OF

bioinstrumentation technology

lab

STERILIZATION USING AUTOCLAVE

UNIVERSITY OF ENGINEERING AND TECHNOLOGY

LAHORE (KSK CAMPUS)

Question no. 1:-

What is sterilization?

Answer:-

Sterilization is a term referring to any process that eliminates or deactivates all forms of life and other biological agents including transmissible agents present in a specified region such as a surface, a volume of fluid, medication or in a compound such as biological culture media.

The concept of what constitutes "sterile" is measured as a probability of sterility for each item to be sterilized. This probability is commonly referred to as the sterility assurance level (SAL) of the product and is defined as probability of a single viable microorganism occurring on a product after sterilization. SAL is normally expressed a 10-n^ (e.g., SAL for blood culture tubes is 10-3^ and 10-6^ SAL

for scalpels, implants).

Question no. 2:-

Describe different types of sterilization?

Answer:-

▲ Sterilization using heat

• Steam sterilization
• Dry heat
• Flaming
• Incineration
• Tyndallization
• Glass bead sterilization

▲ Chemical sterilization

• Ethylene oxide sterilization
• Nitrogen dioxide sterilization
• Ozone sterilization

2. High Speed Pre Vacuum Sterilizer:-

The high speed pre vacuum sterilizers are similar to the gravity displacement sterilizers except they are fitted with a vacuum pump (or ejector) to ensure air removal from the sterilizing chamber and load before the steam is admitted. The advantage of using a vacuum pump is that there is nearly instantaneous steam penetration even into porous loads. The Bowie-Dick test is used to detect air leaks and inadequate air removal and consists of folded 100% cotton surgical towels that are clean and preconditioned.

Microbicidal Activity:-

The oldest and most recognized agent for inactivation of microorganisms is heat. D-values (time to reduce the surviving population by 90% or 1 log10) allow a direct comparison of the heat resistance of microorganisms. Because a D-value can be determined at various temperatures, a subscript is used to designate the exposure temperature (i.e., D121C). D (^) 121C -values for Geobacillus stearothermophilus used to monitor the steam sterilization process range from 1 to 2 minutes. Heat-resistant nonspore-forming bacteria, yeasts, and fungi have such low D121C values that they cannot be experimentally measured.

Mode of Action:- Most heat destroys microorganisms by the irreversible coagulation and denaturation of enzymes and structural proteins. In support of this fact, it has been found that the presence of moisture significantly affects the coagulation temperature of proteins and the temperature at which microorganisms are destroyed.

Uses:-

Steam sterilization should be used whenever possible on all critical items that are heat and moisture resistant (e.g., steam serializable respiratory therapy and anesthesia equipment), even when not essential to prevent pathogen transmission. Steam sterilizers also are used in healthcare facilities to decontaminate microbiological waste and sharps containers but additional exposure time is required in the gravity displacement sterilizer for these items.

Question no. 4:-

What is maximum temperature that most pathogens can withstand?

Answer:-

Kb

Question no. 5:-

Name few fields other than medicines where sterilization is required?

Answer:-

Ha

Question no. 6:-

Explain in detail the chemical sterilization?

Answer:-

Chemical sterilization is used for heat sensitive materials such as biological materials, fiber optics, electronics and many plastics. In these situations chemicals, either as gases or in liquid form, can be used as sterilants. Some examples of chemical sterilization is listed below.

Ethylene dioxide (ETO gas sterilization) Ethylene oxide can kill all known viruses, bacteria (including spores) and fungi, and is compatible with most materials even when repeatedly applied. However, it is highly flammable, toxic and carcinogenic with a potential to cause adverse reproductive effects. Ethylene oxide sterilizers require biological validation after sterilization installation, repairs or process failure. A typical process consists of a preconditioning phase, an exposure phase, and a period of post-sterilization aeration to remove ethylene oxide residues and by-products such as ethylene glycol and ethylene chlorohydrine. The two most important ethylene oxide sterilization methods are: (1) the gas chamber method and (2) the micro-dose method.

Nitrogen dioxide (NO 2 ) gas is a rapid and effective sterilant for use against a wide range of microorganisms, including common bacteria, viruses, and spores. The unique physical properties of NO 2 gas allow for sterilant dispersion in an enclosed environment at room temperature and ambient pressure. The mechanism for lethality is the degradation of DNA in the spore core through nitration of the phosphate backbone, which kills the exposed organism as it absorbs NO 2.

Ozone is used in industrial settings to sterilize water and air, as well as a disinfectant for surfaces. It has the benefit of being able to oxidize most organic matter. On the other hand, it is a toxic and unstable gas that must be produced on- site, so it is not practical to use in many settings.

Glutaraldehyde and formaldehyde solutions are accepted liquid sterilizing agents, provided that the immersion time is sufficiently long. To kill all spores in a clear liquid can take up to 22 hours with glutaraldehyde and even longer with

substantial concrete shields to protect workers and the environment from radiation exposure.

X-rays: high-energy X-rays (produced by bremsstrahlung) allow irradiation of large packages and pallet loads of medical devices. They are sufficiently penetrating to treat multiple pallet loads of low-density packages with very good dose uniformity ratios. X-ray sterilization does not require chemical or radioactive material: high-energy X-rays are generated at high intensity by an X-ray generator that does not require shielding when not in use. X-rays are generated by bombarding a dense material (target) such as tantalum or tungsten with high- energy electrons in a process known as bremsstrahlung conversion. These systems are energy-inefficient, requiring much more electrical energy than other systems for the same result.

Irradiation with X-rays or gamma rays, electromagnetic radiation rather than particles, does not make materials radioactive. Irradiation with particles may make materials radioactive, depending upon the type of particles and their energy, and the type of target material: neutrons and very high-energy particles can make materials radioactive, but have good penetration, whereas lower energy particles (other than neutrons) cannot make materials radioactive, but have poorer penetration.

Question no. 8:-

What is thermal death time. Give two ways to determine it?

Answer:-

Thermal death time is a concept used to determine how long it takes to kill a specific bacteria at a specific temperature.

Thermal death time can be determined one of two ways:

Graphical method :

This is usually expressed in minutes at the temperature of 250 °F (121 °C). This is designated as F (^) 0. Each 18 °F or 10 °C change results in a time change by a factor of 10. This would be shown either as F 10121 = 10 minutes (Celsius) or F^18250 = 10 minutes (Fahrenheit).

A lethal ratio ( L ) is also a sterilizing effect at 1 minute at other temperatures with ( T ).

Where T Ref is the reference temperature, usually 250 °F (121 °C); z is the z- value, and T is the slowest heat point of the product temperature.

Formula method :

Prior to the advent of computers, this was plotted on semilogarithmic paper though it can also be done on spreadsheet programs. The time would be shown on the x-axis while the temperature would be shown on the y -axis. This simple heating curve can also determine the lag factor ( j ) and the slope ( fh ). It also measures the product temperature rather than the can temperature.

Where I = RT (Retort Temperature) − IT (Initial Temperature) and where j is constant for a given product.

It is also determined in the equation shown below:

Where g is the number of degrees below the retort temperature on a simple heating curve at the end of the heating period, B (^) B is the time in minutes from the beginning of the process to the end of the heating period, and f (^) h is the time in minutes required for the straight-line portion of the heating curve plotted semilogarithmically on paper or a computer spreadsheet to pass through a log cycle.

A broken heating curve is also used in this method when dealing with different products in the same process such as chicken noodle soup in having to dealing with the meat and the noodles having different cooking times as an example. It is more complex than the simple heating curve for processing.