Ethylene oxide gas is chosen to sterilise flexible fibreoptic endoscopes that cannot withstand steam. By what mechanism does ethylene oxide achieve microbial killing?

• A Precipitation of microbial proteins
• B Oxidation of sulfhydryl groups by free radicals
• C Coagulation and denaturation of proteins
• D Alkylation of proteins, DNA and RNA ✓

Explanation

Ethylene oxide is an alkylating agent: it attaches hydroxyethyl groups to reactive molecules such as sulfhydryl, amino and hydroxyl groups on microbial proteins and nucleic acids, irreversibly blocking replication and metabolism. Oxidation by free radicals is the mechanism of hydrogen peroxide gas plasma, protein coagulation is the lethal effect of moist heat, and protein precipitation is seen with alcohols and phenols. Because ethylene oxide is toxic and explosive, sterilised items must be aerated before use.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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