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Definition

noun

A biochemical reaction in which anticapsular antibodies bind to the capsule of a bacterium, resulting in the capsule to swell and its outlines becoming clearly demarcated and therefore is more conspicuous, especially under the microscope.

Supplement

It is done especially with bacteria that form capsules, such as Streptococcus pneumoniae and Haemophilus influenzae. The capsule becomes more conspicuous under a microscope after the capsular antigen has combined with a specific antibody.

Word origin: German quellung for "swelling"

Synonyms:

• capsular precipitation reaction
• neufeld capsular swelling
• neufeld reaction
• quellung test
• quellung phenomenon