Definitions for quellung
This page provides all possible meanings and translations of the word quellung
quellung, quellung reaction(noun)
the swelling of the capsule surrounding a microorganism after reaction with an antibody; the basis of certain tests for identifying microorganisms
The Quellung reaction is a biochemical reaction in which antibodies bind to the bacterial capsule of Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Escherichia coli, and Salmonella. The antibody reaction allows these species to be visualized under a microscope. If the reaction is positive, the capsule becomes opaque and appears to enlarge. Quellung is the German word for "swelling" and describes the microscopic appearance of pneumococcal or other bacterial capsules after their polysaccharide antigen has combined with a specific antibody. The antibody usually comes from a bit of serum taken from an immunized laboratory animal. As a result of this combination, and precipitation of the large, complex molecule formed, the capsule appears to swell, because of increased surface tension, and its outlines become clearly demarcated. The pneumococcal Quellung reaction was first described in 1902 by the scientist Fred Neufeld, both as microscopic capsular swelling and macroscopic agglutination. It has been used to identify the 93 known capsular serotypes of Streptococcus pneumoniae in a diagnostic setting, but in recent years has been challenged by molecular typing techniques which target genetic differences.
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