Meningitis caused by gram-negative bacilli.

Thirty adults with meningitis caused by gram-negative bacilli were observed from 1968 to 1978 at four hospitals associated with Boston University School of Medicine. Equal numbers of two distinct types of gram-negative bacillary meningitis--spontaneously occurring meningitis and meningitis after neurosurgery--were found. Spontaneously occurring meningitis appeared to be caused most often by Escherichia coli and Haemophilus influenzae. Meningitis occurring after neurosurgical procedures was more insidious in onset, more protracted in course, and more often caused by organisms resistant to multilple antibiotics. Approaches to therapy are based on the differences in character of these two types of meningitis.