Definition

1. Noun:
   • A specific immunological reaction: The "quellung reaction" is a laboratory phenomenon where the capsule surrounding certain bacteria visibly swells when exposed to specific antibodies. This swelling is used to identify the bacterial species or serotype.

Usage

• The "quellung reaction" is a technical term used primarily in microbiology, immunology, and medical diagnostics.
• It describes a confirmatory test result. One observes to identify an organism.
• It is often used with the name of the bacterium being identified (e.g., pneumococcus quellung).

Examples

• Noun:
  • The laboratory confirmed the presence of Streptococcus pneumoniae by observing a positive quellung reaction.
  • The quellung reaction forms the basis of the Neufeld test for typing pneumococci.

Advanced Usage

• "To demonstrate a quellung reaction": This phrase is used to describe the action of performing the test and obtaining a positive result.
  • The antiserum caused the capsule to swell, demonstrating a clear quellung reaction.

Variants and Related Words

• Quellung (noun): Sometimes used alone as a shorter form to refer to the same swelling phenomenon.
  • Capsular quellung is a key diagnostic feature.
• Neufeld reaction (noun): A synonym, named after the bacteriologist who described it.
• Capsular swelling test (noun): A descriptive synonym for the procedure.

Synonyms

• Capsular swelling reaction: A more descriptive synonym.
• Neufeld test: Specifically refers to the test procedure that relies on the quellung reaction.

Notes on Meaning

• The term is highly specific to a single laboratory technique and result. It does not have general or figurative meanings.
• The core concept is the visible, antibody-induced swelling ( is German for "swelling") of a bacterial capsule, which allows for microscopic identification.

Noun

1. the swelling of the capsule surrounding a microorganism after reaction with an antibody; the basis of certain tests for identifying microorganisms
   • pneumococcus quellung