National Center for Biotechnology Information NCBI NLM MEDLINE humans pubmed abstract nih national institutes of health national library of medicine adult adolescent aged middle aged Recurrence risk factors 80 and over acute disease meningitis boston hospital mortality pneumococcal infections / mortality bacterial / mortality* bacterial / cerebrospinal fluid cross infection / mortality* gram-negative bacterial infections / mortality gram-negative bacterial infections / cerebrospinal fluid pmid:8416268 doi:10.1056/nejm199301073280104 m l durand s b calderwood m n swartz gram-negative bacterial infections / transmission seizures / etiology