Which method helps achieve complete sterilisation?

Appeared in: BTSC 3 August 2025

Explanation

Sterilization is a process that eliminates all forms of microbial life, including highly resistant bacterial spores.
Autoclaving uses pressurized steam (moist heat) at 121°C and 15 psi, which effectively penetrates materials and kills all microorganisms by denaturing their proteins.
This method is considered the gold standard for sterilizing heat-resistant medical equipment and surgical instruments to ensure surgical asepsis.

Option B: 70% alcohol is a chemical disinfectant, not a sterilant. It is effective against vegetative bacteria and viruses but cannot destroy bacterial spores.
Option C: UV light is a form of radiation used for disinfection. It has very poor penetrating power and its effectiveness is reduced by shadows or soiling, making it unreliable for sterilizing instruments.
Option D: Chlorine is a powerful disinfectant used for water treatment and surface cleaning. While high concentrations can be sporicidal (acting as a chemical sterilant), the term 'chlorine disinfection' generally refers to a process that does not guarantee complete sterilization.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Methods of Sterilization vs. Disinfection as background academic context rather than a clinical decision trigger.
Understanding the difference between sterilization and disinfection is fundamental to infection control and preventing healthcare-associated infections (HAIs).
Nurses are responsible for ensuring that medical equipment is processed correctly. Using a disinfected instrument for a procedure that requires a sterile one can lead to severe patient infections.
What if? If an instrument is heat-sensitive (e.g., a flexible endoscope) and cannot be autoclaved, a nurse would need to use a low-temperature sterilization method like ethylene oxide (ETO) gas or hydrogen peroxide gas plasma to achieve sterility.

How to Approach the Question

First, identify the key term in the question: 'complete sterilisation'. This is a precise term meaning the elimination of ALL microbial life, including spores.
Evaluate each option against this strict definition.
Recall that autoclaving uses steam under pressure, a method known for its ability to kill even the most resistant spores.
Recognize that alcohol, UV light, and chlorine are common disinfectants, which reduce microbial counts but are not typically sporicidal.
Conclude that autoclaving is the only method listed that reliably achieves complete sterilization.

Concept Tested & Keywords

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

E6 Microbiology OneStop Sastry p. 50-52

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