Presence of a capsule in Neisseria lactamica, antigenically similar to the capsule of N. meningitidis

Three of thirteen strains of Neisseria lactamica, a species closely related to N. meningitidis, were selected on the basis of their ability to be strongly agglutinated by serogroup B antimeningococcal serum. The presence of a capsule was demonstrated using Alcian blue as a stain for acidic polysaccharide. When reacted with serogroup B antimeningococcal sera, 2 out of 3 N. lactamica B-coagglutanating strains exhibited an extracellular material comparable in size, antigenicity and staining properties to the capsule of serogroup B N. meningitidis.