Neisseria meningitidis

a prominent cause of meningitis and the specific etiologic agent of meningococcal meningitis; it can also cause meningococcal pneumonia, a type of bacterial pneumonia (see under pneumonia). Species can be differentiated serologically into at least 13 groups (A, B, C, D, E, H, I, K, L, W-135, X, Y, and Z); groups A, B, and C are responsible for most cases of disease, with B and C being predominant in Europe and the Americas and A and C predominant in Asia and Africa.