MICROSCOPIC EXAMINATION AND BROTH CULTURE OF CEREBROSPINAL-FLUID IN DIAGNOSIS OF MENINGITIS

We reviewed the results of microscopic Gram stain examination and rout ine culture for 2,635 cerebrospinal fluid (CSF) samples processed in a n adult hospital microbiology laboratory during 55 months, There were 56 instances of bacterial or fungal meningitis (16 associated with cen tral nervous system [CNS] shunt infection), four infections adjacent t o the subarachnoid space, four cases of sepsis without meningitis, and an additional 220 CSF specimens with positive cultures in which the o rganism isolated was judged to be a contaminant, Because 121 of these contaminants were isolated in broth only, elimination of the broth cul ture would decrease unnecessary work. However, 25% of the meningitis a ssociated with CNS shunts would have been missed by this practice. The most common cause of meningitis was Cryptococcus neoformans, followed by Streptococcus pneumoniae and Neisseria meningitidis., In 48 of 56 (88%) of cases, examination of the Gram-stained specimen revealed the causative organism. If patients who had received effective antimicrobi al therapy prior to lumbar puncture are excluded, the CSF Gram stain i s 92% sensitive. Microscopic examination incorrectly suggested the pre sence of organisms in only 3 of 2,635 (0.1%) CSF examinations. Thus, m icroscopic examination of Gram-stained, concentrated CSF is highly sen sitive and specific in early diagnosis of bacterial or fungal meningit is.