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Neonatal Meningitis: Do We Have a Clue?

Several features can distinguish meningitis caused by gram-negative rods from that caused by gram-positive cocci.

A presumptive diagnosis of neonatal meningitis requires prompt treatment, and clinicians must often choose an antibiotic regimen before knowing the definitive diagnosis. Using a national database, investigators examined discharge records from 150 neonatal intensive care units to determine whether laboratory and clinical parameters could distinguish between meningitis caused by gram-positive cocci (GPC) and gram-negative rods (GNR).

Researchers evaluated results from 14,017 lumbar punctures performed from 1997 to 2004: 86 infants were infected with GPC, and 77 were infected with GNR. Data from infants with shunts and cerebral spinal fluid (CSF) reservoirs were excluded. Overall, 38% of the infants were very-low-birth-weight, and 56% were preterm. Birth weight, gestational age, sex, race, and mode of delivery did not differ between infants with GPC and GNR meningitis. Infants who underwent lumbar puncture after the third day of life were more likely to have GNR meningitis.

Among infants diagnosed with meningitis within the first 3 days of life, 69% of those exposed to antepartum antibiotics were infected with GNR, versus only 30% of those with no antibiotic exposure. Infants with GNR meningitis had significantly higher median CSF white blood cell counts (1217/mm³ vs. 187/mm³) and red blood cell counts (465/mm³ vs. 160/mm³) than infants with GPC. CSF protein content and glucose concentrations did not differ between the two groups. Mortality was higher in GNR infants than in GPC infants (13% vs. 4%). The authors concluded that GNR meningitis in the newborn is associated with older age at presentation, antepartum exposure to antibiotics, and elevated WBC and RBC counts.

Comment: I was disappointed that the authors did not include Gram stain of CSF as a parameter; a positive result on this test can be very helpful for differentiating between GPC and GNR, for diagnosing meningitis, and for determining which antibiotic to use in newborns pending culture results. CSF culture is still the gold standard for diagnosing neonatal meningitis. Clinicians are reminded to obtain specimens before starting antibiotic therapy.

— William P. Kanto, Jr., MD

Published in Journal Watch Pediatrics and Adolescent Medicine April 21, 2006

Citation(s):

Smith PB et al. A comparison of neonatal gram-negative rod and gram-positive cocci meningitis. J Perinatol 2006 Feb; 26:111-4.

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