- Quellung Test is an increase in the opacity and visibility of the capsule of encapsulated organisms resulting from exposure to specific, agglutinating, anticapsular antibodies. This test is also called Neufeld reaction or quellung reaction. This test is usually used to diagnose pneumococci infection.
Swollen Pneumococci Capsule
Photomicrograph of Streptococcus pneumoniae bacteria revealing capsular swelling using the Quellung test
