Polysaccharide encapsulated bacteria, frequently referred to simply as encapsulated bacteria and less precisely called encapsulated organisms, are a group of bacteria that have an outer covering, a capsule, made of polysaccharide.

Do all bacteria have a capsule?

Not all bacterial species produce capsules; however, the capsules of encapsulated pathogens are often important determinants of virulence. Encapsulated species are found among both Gram-positive and Gram-negative bacteria.

What bacteria are not encapsulated?

Among the enterobacteries not having capsules one can quote : Pseudomonas aeruginosa, Shiguelles, Vibrio cholerae which are gram negative bacteria. In the family of Neisseriaceae one can quote Haemophilus ducrey and H. aegyptius which are also gram negative bacilli and which are not capsuled.