Which is an example of sterilisation below 100°C?

Appeared in: PGICH Noida NO-2025

Explanation

Pasteurisation is a low-temperature moist heat method used to eliminate pathogens from liquids like milk.
It operates at temperatures significantly below 100°C, such as 63°C for 30 minutes (Holder method) or 72°C for 15-20 seconds (Flash method).
While it does not achieve true sterilization (as it doesn't kill spores), it is the only option that fits the temperature criteria of 'below 100°C'.

Option A: Autoclaving uses steam under high pressure to achieve temperatures well above 100°C (typically 121°C), making it a high-temperature sterilization method.
Option B: Boiling occurs exactly at 100°C at standard pressure, not below it. It is a disinfection method, not a reliable sterilization method.
Option C: Tyndallisation, or intermittent sterilization, involves heating at 100°C for a period on three successive days. The temperature used is 100°C, not below it.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Methods of sterilization by moist heat as background academic context rather than a clinical decision trigger.
Understanding the correct temperature and method for decontamination is a fundamental nursing responsibility for infection control and patient safety.
Selecting an inappropriate method, such as pasteurizing a surgical instrument, would fail to sterilize it and could lead to a severe healthcare-associated infection (HAI).
Nurses must be able to differentiate between disinfection (reducing harmful microbes) and sterilization (eliminating all microbes) to ensure items are safe for their intended use.

How to Approach the Question

First, identify the key phrase in the question: 'below 100°C'. This is the main condition the answer must satisfy.
Second, systematically review each option and recall its standard operating temperature.
Recall that Autoclaving uses steam under pressure and is much hotter than 100°C.
Recall that Boiling occurs at 100°C.
Recall that Tyndallisation is a process of repeated heating at 100°C.
Recall that Pasteurisation is used for milk and other foods at temperatures like 63°C or 72°C.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) pp. 127-129, 129-131

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