Boiling water helps in killing all the organisms, except?

RUHS, Jaipur, PB B.Sc Nursing Entrance-2018

Applied Microbiology & Infection control

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2018

Explanation

Spores, specifically bacterial endospores, are highly resistant dormant structures with a tough, multi-layered protective coat.
This coat allows them to survive harsh environmental conditions, including boiling at 100°C, which is a method of disinfection, not sterilization.
To destroy spores, sterilization methods like autoclaving are required, which use steam under pressure to achieve higher temperatures (e.g., 121°C).

Option B: Most fungi, including their vegetative cells and spores (different from bacterial endospores), are readily killed by boiling for a few minutes.
Option C: The vegetative (active, growing) forms of almost all pathogenic bacteria are killed by boiling water within minutes.
Option D: Protozoa and their dormant cyst forms (e.g., Giardia, Cryptosporidium) are effectively inactivated or killed by bringing water to a rolling boil.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Principles of Sterilization and Disinfection as background academic context rather than a clinical decision trigger.
Understanding the difference between disinfection and sterilization is fundamental to infection control and patient safety. Using a disinfected (boiled) instrument for a procedure that requires sterility can lead to life-threatening infections.
In home care or low-resource settings, boiling is a practical method for high-level disinfection of non-critical items like feeding equipment, but it is never a substitute for sterilization of critical items like surgical instruments.
What if? If the question asked about making drinking water safe during a boil-water advisory, boiling would be the correct action because it effectively kills common waterborne pathogens like bacteria (E. coli), protozoa (Giardia), and most viruses.

How to Approach the Question

First, identify the negative keyword 'except'. This signals that you must find the one option that does NOT fit the statement.
The core statement is that boiling water kills organisms. Therefore, the task is to find the organism that survives boiling.
Recall the hierarchy of microbial resistance to decontamination methods. Bacterial spores are known to be the most resistant forms of microbial life.
Evaluate each option against this knowledge: Fungi, vegetative bacteria, and protozoa are all susceptible to heat and are killed by boiling.
Recognize that spores are specifically designed for survival in extreme conditions, including temperatures of 100°C.
Conclude that spores are the correct exception as they are not reliably killed by boiling.

Concept Tested & Keywords

Concept Tested: Principles of Sterilization and Disinfection
Stem keywords: Boiling water, killing organisms
Lead-in keywords: except
Negative lead-in flag: The question asks for the exception, meaning the organism that is NOT killed by boiling.

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