Neisseria meningitidis bacteria. Coloured scanning electron micrograph (SEM) of Neisseria meningitidis bacteria, one of the causes of meningitis. They are non-motile, Gram-negative cocci (spherical) bacteria. N. meningitidis is an obligate human parasite and the cause of meningococcal (cerebrospinal) meningitis, the inflammation of the connective tissue membranes lining the brain and spinal cord. Symptoms include intense headache, fever, muscle rigidity and, in severe cases, convulsions and delirium leading to death. Bacterial meningitis is treated with large doses of antibiotics. Magnification: x21,000 at 6x4.5cm size.