Outer-Membrane Components Associated with Virulence Meningococcal strains are characterized by the expression of capsular polysaccharide and other outer-membrane structures, including LOS (endotoxin). Outer-membrane blebbing, meningococcal autolysis, molecular mimicry, genome plasticity, horizontal DNA exchange, and phase and/or antigenic variation are all important in meningococcal virulence. Capsule The polysaccharide capsule is a major—if not the major—virulence factor of N. meningitidis. As stated above, meningococci isolated from the blood or cerebrospinal fluid (CSF) of patients with invasive meningococcal disease most often express capsules of serogroups A, B, C, Y, and W-135. Isolates from asymptomatic nasopharyngeal carriers are nongroupable or express B, Y, X, Z,.
