Attempts to demonstrate a polysaccharide capsule in Neisseria gonorrhoeae

The presence or absence of a polysaccharide capsule on the human pathogen Neisseria (N.) gonorrhoeae is still a topic of controversy. For this reason we compared the results obtained by light microscopy (dry India ink-Fuchsin stain) and electron microscopy (Alcian blue-lanthanum nitrate stain) of encapsulated strains of N. meningitidis and Streptococcus (S.) pneumoniae and of non-encapsulated strains of S. pneumoniae and Escherichia (E.) coli with those obtained using the same methods on strains of pilliated and non-pilliated N. gonorrhoeae. After staining with India ink-Fuchsin no capsules could be demonstrated on any of the N. gonorrhoeae strains studied. If present the capsules on these cells are too delicate to be identified by light microscopy. After treatment with Alcian blue-lanthanum nitrate sections of cells of N. meningitidis and S. pneumoniae generally showed the presence of a capsular layer. Sections of cells of the non-encapsulated strain of S. pneumoniae which possess C (common)-polysaccharide also showed surface associated capsule-like material. Similarly the surface of the cells of the E. coli strain showed material which appeared to be tufts of pili and/or M (mucoid)-antigen. In experiments where the N. gonorrhoeae cells were harvested as early as after six hours of growth a capsule-like material was demonstrated on cells of all strains studied.