- The Quellung reaction is primarily used to identify Streptococcus pneumoniae by detecting its polysaccharide capsule.
- When specific anti-capsular antibodies bind to the capsule, it causes the capsule to appear swollen and more refractile under a microscope.
- This reaction is a rapid and specific method to differentiate S. pneumoniae from other bacteria, as the capsule is a major virulence factor and unique to pneumococci in this context.
- Other organisms listed do not typically exhibit a visible capsular swelling in the Quellung test.