Test: Sterilization and Disinfection - NEET PG MCQ

Geobacillus stereothermophilus and Bacillus subtilis subsp. niger are employed as biological indicators for sterilisation.

Filtration is the most effective technique for sterilising heat-sensitive liquids, including sera and solutions containing sugars, antibiotics, toxins, and vaccines. It plays a crucial role in eliminating bacteria.

• Biological sterilisation indicator for autoclaves: B. stearothermophilus
• Hot air oven: Clostridium tetani nontoxigenic strain

Autoclave: The suggested conditions are:

• Temperature of 121–124°C for 15 minutes at 1.1 bar pressure.
• Alternatively, a temperature of 134–138°C for 3 minutes at 2.2 bar pressure.
• Hot air oven: A temperature of 160°C for 120 minutes or 180°C for 30 minutes is recommended.

Prions represent the most resistant form of structure.

• Isopropyl alcohol and phenol serve as intermediate-level disinfectants.
• Quaternary ammonium compounds, such as Benzalkonium chloride, act as low-level disinfectants.
• Glutaraldehyde, formaldehyde, hydrogen peroxide, and chlorine function as high-level disinfectants.

Heart-lung machines, respirators, and dental equipment are most effectively sterilised using ethylene oxide.

2% Glutaraldehyde and Ophthaldehyde are suggested disinfectants for endoscopes.

Prions can be sterilised using the following methods:

• 0.5% Hypochlorite for 2 hours
• 1N NaOH for 1 hour
• Autoclave at 134°C for 1 to 1.5 hours

A fiberoptic is a pliable, clear fibre crafted from premium extruded glass (silica) or plastic, utilised in laryngoscopes. Fiberoptic laryngoscopes are most effectively sterilised using Glutaraldehyde or ortho-ophthaldehyde.

Semicritical items are defined as those that touch mucous membranes or minor breaches in the skin. These items require a high to intermediate level of disinfectant for proper sterilisation.

For further information, refer to Spaulding's criteria regarding devices.

Evaluating the effectiveness of disinfectants using the Phenol coefficient (Rideal Walker) test involves calculating the Phenol coefficient by:

• Finding the dilution of the disinfectant that successfully sterilises the suspension of S. Typhi within a specified time.
• Dividing this dilution by the dilution of phenol that achieves sterilisation in the same timeframe.

The most frequently suspected pathogen found in sputum is tubercle bacilli. Therefore, it needs to be disinfected using a suitable technique. Chlorhexidine is an antiseptic for the skin, commonly employed for treating burns or for hand disinfection; however, it is not mycobactericidal. Sputum can be disinfected through the following methods:

• Autoclaving: The optimal method.
• Other methods include:
• Incineration of the material,
• Using 5% cresol or phenol, or
• Boiling.

Steam is the favoured technique for sterilising essential medical and surgical tools that can withstand heat, steam, pressure, or moisture.

Metal instruments and surgical blades are more effectively sterilised using an autoclave.

• Benzalkonium chloride serves as a surface-active substance.
• It is commonly utilised as a wetting agent, detergent, and emulsifier.

Savlon comprises:

• Cetrimide 3% (Cetavlon)
• Chlorhexidine 0.3% (Hibitane)