Purulent meningitis is a medical emergency in which prompt and accurate diagnosis and rapid institution of appropriate antibacterial therapy are essential to preserve life and to prevent serious and disabling sequelae. Microscopic examination of the stained cerebrospinal fluid sediment is a key to the correct, rapid identification of the microorganism responsible for the meningitis. This initial impression is confirmed when the organism noted on slides can be cultured and identified with greater precision. In clinical practice, however, these two examinations are sometimes neither satisfactory nor conclusive.
Haggerty 1 has pointed out that even in experienced hands a 10% error is inherent in examination of the Gram-stained spinal fluid smear; additionally, no organism is seen on smear but the culture will yield a causative organism in 25% of cases; in 15% no organism is identified on smear or on culture. Meningococci are very delicate organisms and their survival can be jeopardized
GROSSMAN M, SUSSMAN S, GOTTFRIED D, OUOCK C, TICKNOR W. Immunofluorescent Techniques in Bacterial MeningitisIdentification of Neisseria Meningitidis and Hemophilus Influenzae. Am J Dis Child. 1964;107(4):356–362. doi:10.1001/archpedi.1964.02080060358006