Sterilisation

Sterilisation

Sterilisation is a critical process in the medical field, aimed at eliminating all forms of microbial life, including bacteria, viruses, fungi, and spores, from surfaces, instruments, and environments. This process is essential in preventing infections and ensuring the safety of medical procedures.

Methods of Sterilisation

Sterilisation can be achieved through various methods, each suitable for different types of materials and applications. The main methods include:

Heat Sterilisation

Heat is one of the most common methods of sterilisation, and it can be applied in two forms:

• Moist Heat Sterilisation: This method uses steam under pressure, typically in an autoclave, to achieve sterilisation. The standard conditions are 121°C at 15 psi for 15-20 minutes. Moist heat is effective because it denatures proteins and destroys microorganisms.

• Dry Heat Sterilisation: This involves the use of hot air ovens, where items are exposed to high temperatures (160-180°C) for extended periods (1-2 hours). Dry heat is suitable for materials that might be damaged by moisture, such as powders and oils.

Chemical Sterilisation

Chemical sterilisation involves the use of chemical agents to kill microorganisms. Common chemical sterilants include:

• Ethylene Oxide Gas: Used for heat-sensitive materials, ethylene oxide is a potent sterilant that can penetrate packaging and complex devices.

• Hydrogen Peroxide Plasma: This method uses vaporized hydrogen peroxide, which is converted into plasma to sterilise equipment. It is effective and leaves no toxic residues.

• Glutaraldehyde: A liquid chemical sterilant used for heat-sensitive medical equipment. It requires immersion of items for a specific period.

Radiation Sterilisation

Radiation sterilisation uses ionizing radiation to destroy microorganisms. The two main types are:

• Gamma Radiation: Utilizes gamma rays from sources like Cobalt-60. It is used for sterilising disposable medical supplies, such as syringes and surgical gloves.

• Electron Beam Radiation: Uses high-energy electrons to sterilise items. It is faster than gamma radiation and suitable for large-scale sterilisation.

Filtration

Filtration is used to sterilise liquids and gases that cannot be heated. It involves passing the fluid through a filter with pores small enough to remove microorganisms. This method is commonly used for heat-sensitive pharmaceuticals and culture media.

Applications of Sterilisation

Sterilisation is crucial in various settings, including:

• Hospitals: To sterilise surgical instruments, linens, and other equipment to prevent nosocomial infections.

• Pharmaceutical Industry: To ensure that drugs and vaccines are free from contaminants.

• Laboratories: To maintain sterile conditions for experiments and culture work.

Challenges in Sterilisation

Despite its importance, sterilisation faces several challenges:

• Resistance: Some microorganisms, such as bacterial spores, are highly resistant to sterilisation methods.

• Material Compatibility: Not all materials can withstand all sterilisation methods, requiring careful selection of techniques.

• Validation and Monitoring: Ensuring that sterilisation processes are effective requires rigorous validation and monitoring.

Also see

• Disinfection
• Aseptic technique
• Nosocomial infection
• Autoclave
• Infection control