Inoculating loops are sterilized by?

BHU NO - 2015

Applied Microbiology & Infection control

Easy

Appeared in: BHU NO - 2015

Explanation

Flaming is the standard and most effective method for sterilizing metal inoculating loops in a microbiology laboratory.
The process involves heating the loop directly in a flame, typically from a Bunsen burner, until it glows red-hot.
This intense heat causes incineration, which completely destroys all forms of microbial life, including highly resistant bacterial spores.
It is a rapid, point-of-use technique that allows for immediate reuse of the loop, which is essential for aseptic culture transfer techniques.

Option A: A hot air oven uses dry heat over a prolonged period (1-2 hours), making it unsuitable for the rapid, repeated sterilization required for an inoculating loop during laboratory work.
Option B: An autoclave uses moist heat (steam under pressure) and is not practical for the immediate sterilization of an inoculating loop at a workbench. The cycle time is too long.
Option D: Radiation is an industrial-scale sterilization method used for pre-packaged, single-use items. It is not used for reusable laboratory equipment like metal inoculating loops.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Sterilization methods in microbiology as background academic context rather than a clinical decision trigger.
In a clinical microbiology lab, correct sterilization of inoculating loops is critical to prevent cross-contamination of patient samples.
Failure to properly sterilize a loop can lead to the transfer of microbes from one culture to another, resulting in misidentification of pathogens, incorrect antibiotic susceptibility results, and ultimately, a wrong diagnosis and treatment for the patient.
What if? - If a laboratory uses disposable plastic inoculating loops instead of metal ones, they must not be flamed. These loops are supplied sterile and are designed for single use only; they must be discarded into a designated biohazard container after use.

How to Approach the Question

First, identify the item in the question: an 'inoculating loop'. Recognize this as a common tool in microbiology for transferring microorganisms.
Next, consider the context of its use. It is used repeatedly at a lab bench to transfer cultures, so the sterilization method must be rapid and effective at the point of use.
Evaluate each option based on this requirement.
Flaming provides instantaneous sterilization, making it ideal for this purpose.
Hot air oven and autoclave are batch sterilization methods that require long cycles (hours), making them impractical for this specific, repetitive task.
Radiation is an industrial method for sterilizing pre-packaged disposables and is not applicable to reusable benchtop tools.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) pp. 126-128, 127-129