Those of us who believe in the unvarying beneficence of Mother Nature have yet to contemplate Neisseria meningitidis. N. meningitidis is a bacterium that can live harmlessly in the throats of healthy people. But about 500 times a year in the US it causes bacterial meningitis, a life-threatening infection in which the membranes lining the brain and spinal cord become inflamed. Bacterial meningitis is treatable with antibiotics but even with treatment patients sometime suffer...