Steaming of material at 100°C for 20 minutes for 3 consecutive days is

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2023

Applied Microbiology & Infection control

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2023

Explanation

Tyndallisation, also known as fractional sterilization, is defined as heating a substance to 100°C for a set period over three consecutive days.
The process is designed to kill vegetative bacteria on the first day and then, after an incubation period allows resistant spores to germinate, kill the newly formed vegetative cells on subsequent days.
This method is specifically used for sterilizing materials, like culture media with sugars, that cannot withstand the higher temperatures of an autoclave.

Option A: Inspissation uses a lower temperature (80-85°C) than the 100°C specified in the question.
Option C: Pasteurisation is a disinfection process, not sterilization. It uses lower temperatures (e.g., 63°C or 72°C) and does not eliminate bacterial spores.
Option D: Incineration is a dry heat method that involves burning materials to ash for disposal. The question describes steaming, which is a moist heat method.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Moist heat sterilization methods as background academic context rather than a clinical decision trigger.
In a laboratory or clinical setting, choosing the correct sterilization method is critical for patient safety and the validity of diagnostic tests.
Tyndallisation is essential for preparing certain culture media that are heat-sensitive and would be damaged by autoclaving (e.g., media with sugars or gelatin), ensuring they are sterile yet still functional.
What if the material to be sterilized was a set of stainless steel surgical instruments? In that case, autoclaving (steam under pressure at 121°C) would be the preferred method as it is faster, more reliable, and achieves sterility in a single cycle by killing both vegetative cells and spores.

How to Approach the Question

First, identify the key parameters given in the question stem: the method (steaming), the temperature (100°C), the duration (20 minutes), and the frequency (3 consecutive days).
This is a factual recall question that requires knowledge of different sterilization and disinfection techniques.
Systematically evaluate each option against the parameters. 'Steaming at 100°C' points to moist heat at atmospheric pressure.
The detail '3 consecutive days' is the most unique identifier. Recall the sterilization method that uses intermittent heating to deal with bacterial spores.
Match the complete definition (100°C, intermittent heating over 3 days) to the correct term, which is Tyndallisation.

Concept Tested & Keywords

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