The process by which a medium is placed at 100°C following steam for 20 minutes each on 3 successive days is?

AIIMS Raipur NO - 2017 (Shift-1)

Applied Microbiology & Infection control

Easy

Appeared in: AIIMS Raipur NO - 2017 (Shift-1)

Explanation

The question describes the exact parameters for Tyndallization: heating with steam at 100°C for a short duration on three consecutive days.
This process is also known as fractional or intermittent sterilization.
The principle is to kill vegetative cells in the first heating, allow heat-resistant spores to germinate into vegetative cells during the incubation period, and then kill these new cells in subsequent heatings.
It is used for substances that cannot withstand the higher temperatures of an autoclave, such as media containing egg or serum.

Option A: Steam under pressure is another term for autoclaving. This process uses temperatures higher than 100°C (typically 121°C) and is completed in a single cycle, which does not match the question's description of a three-day process at 100°C.
Option B: An autoclave uses steam under pressure to achieve a temperature of 121°C for 15-20 minutes in a single session. The question specifies a temperature of 100°C and a three-day cycle.
Option D: Inspissation is a process of heating at a lower temperature (around 80-85°C) for a longer duration, often for several hours on successive days. Its primary purpose is to solidify and sterilize media containing proteins like egg or serum, such as the Lowenstein-Jensen medium. The temperature is different from the 100°C mentioned in the question.

Visual 1: Flowchart - A flowchart illustrating the three-day cycle of Tyndallization, showing the heating, incubation, and spore germination steps for each day.
Visual 2: Comparison Table - A table comparing the parameters (temperature, pressure, time) and uses of Tyndallization, Autoclaving, and Inspissation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Methods of Sterilization as background academic context rather than a clinical decision trigger.
Understanding different sterilization methods is crucial for nurses and lab technicians to ensure that medical equipment and culture media are free from microorganisms, preventing infections and ensuring accurate lab results.
Tyndallization is essential in microbiology labs for preparing specific culture media (e.g., for certain bacteria) that are heat-sensitive and would be destroyed by autoclaving.
What if? - If a nurse needed to sterilize a heat-sensitive liquid that could not be filtered, Tyndallization would be the appropriate method, whereas using an autoclave would denature the components and render the liquid useless.

How to Approach the Question

First, carefully read the question and identify the key parameters of the process described: temperature (100°C), method (steam), duration (20 minutes), and frequency (3 successive days).
Next, evaluate each option based on your knowledge of sterilization techniques.
Recall the definition of an Autoclave (Steam under pressure), which uses higher temperatures (121°C) and pressure in a single cycle.
Recall the definition of Inspissation, which uses lower temperatures (80-85°C).
Recognize that the process of intermittent heating at 100°C over three days to kill spores is the definition of Tyndallization.
Select the option that perfectly matches all the parameters given in the stem.

Concept Tested & Keywords

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