A public health laboratory receives samples of animal hides and meat suspected of being contaminated with Bacillus anthracis. Which classical serological test, performed by overlaying a boiled aqueous extract of the specimen with hyperimmune anti-anthrax serum, would demonstrate a ring of precipitation?

• A Schick test
• B Nagler's reaction
• C Dick test
• D Ascoli's thermoprecipitation test ✓

Explanation

The Ascoli test is a ring (thermal) precipitin reaction in which a clear extract of infected tissue, hide or meat is layered under anti-anthrax serum; a white ring at the interface within minutes confirms Bacillus anthracis antigen. It remains useful when cultures cannot be obtained from processed material. Nagler's reaction identifies Clostridium perfringens alpha toxin on egg yolk agar, while the Dick and Schick tests relate to streptococcal and diphtherial toxins, killing those distractors.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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