Neonatal meningitis: what is the correlation among cerebrospinal fluid cultures, blood cultures, and cerebrospinal fluid parameters?

BACKGROUND: Meningitis is a substantial cause of morbidity and mortality in neonates. Clinicians frequently use the presence of positive blood cultures to determine whether neonates should undergo lumbar puncture. Abnormal cerebrospinal fluid (CSF) parameters are often used to predict neonatal meningitis and determine length and type of antibiotic therapy in neonates with a positive blood culture and negative CSF culture.

METHODS: We evaluated the first lumbar puncture of 9111 neonates at > or =34 weeks' estimated gestational age from 150 NICUs, managed by the Pediatrix Medical Group, Inc. CSF culture results were compared with results of blood cultures and CSF parameters (white blood cells [WBCs], glucose, and protein) to establish the concordance of these values in culture-proven meningitis. CSF cultures positive for coagulase-negative staphylococci and other probable contaminants, as well as fungal and viral pathogens, were excluded from analyses.

RESULTS: Meningitis was confirmed by culture in 95 (1.0%) neonates. Of the 95 patients with meningitis, 92 had a documented blood culture. Only 57 (62%) of 92 patients had a concomitant-positive blood culture; 35 (38%) of 92 had a negative blood culture. In neonates with both positive blood and CSF cultures, the organisms isolated were discordant in 2 (3.5%) of 57 cases. In each case, the CSF pathogen required different antimicrobial therapy than the blood pathogen. For culture-proven meningitis, CSF WBC counts of >0 cells per mm3 had sensitivity at 97% and specificity at 11%. CSF WBC counts of >21 cells per mm3 had sensitivity at 79% and specificity at 81%. Culture-proven meningitis was not diagnosed accurately by CSF glucose or by protein.

CONCLUSIONS: Neonatal meningitis frequently occurs in the absence of bacteremia and in the presence of normal CSF parameters. No single CSF value can reliably exclude the presence of meningitis in neonates. The CSF culture is critical to establishing the diagnosis of neonatal meningitis.